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fuel fire desire
March 08, 2017, 12:41
(New issue with charging handle at bottom of thread)



Even though I told myself 5 years ago I would not build another AR after selling everything I had AR related....here I am...


I had a very nice receiver fall into my lap I wasn't expecting, and am looking to go a route I haven't gone before. I'm trying to build a sub 6 pound 16" AR for no other purpose than being a fast shooting range toy. Mind you, all my other AR builds were fairly basic, sticking to Mil-Spec parts. So this would be my first venture into building what amounts to be a race gun.

I'll call this my build thread showing progress as I go, but I'll also use it to post questions as I'm sure I'll have a few being new to ultralight builds. This way I won't have 5 threads asking questions about the same gun.


To start off, here's the goal: Lightweight fast shooting 16" 5.56 that comes in around $1500 on a receiver I already have. I don't mind spending money on parts, but don't want to spend 50-100% more on a titanium part where a weight savings is only a very small amount.


Here's the parts list:

Lower:
(Parts on order already)


Assembled ambi billet lower -9.4oz -
ARUL ultralight stock - 6.8oz -
Taccom rifle recoil system - 2.0oz -
Taccom reduced rate spring - 1.8oz -
Safety selector. - 0.5oz -
Magpul MOE grip. - 2.8oz -
CMC drop in trigger. - 3.2oz -


Upper:



Matching assembled billet upper. - 8.2oz -
Strike industries charging handle. -1.2oz -
Faxon lightweight BCG. - 8.5oz -
Vella industries trident 16.5" hand guard - 11.5oz -
Faxon 16" SS pencil barrel - 19oz -
SLR adj. .625" gas block/ mid tube. - 2.0oz-
Precision armament m4-72 brake - 2.6oz -



Total: 79.5oz/ 4.9lbs, with no optic.

Am I missing anything/ on the right road? Any input would be appreciated!




GASSING QUESTION:

Since I am going with a lighter than usual BCG by 2 ounces, I can foresee having some overgassing issues. Since the goal is lightweight, I'd rather not add weight to the buffer to compensate....it defeats the purpose. I thought that if I used a mid length gas system instead of the typical carbine length on a 16" barrel, the reduced dwell time would lower the amount of gas going into the bolt and help the issue. Am I on the right train of thought? Does anyone think that an adjustable gas block might be needed in addition to this?

Standard A2 spring and buffer, 8.5 ounce BCG (skeletonized, not Ti)



Of course build pics to come......

CG&L
March 08, 2017, 13:39
I use adjustable gas blocks on all AR builds. Not just my ARs but customer builds as well

With the mods you want, it's possible your rifle will run OK without an adj gas block. I wouldn't bet any money on it. I use and recommend the SLR Rifleworks adjustable gas block.

A light weight build should run around $1,100. It's my own personal opinion but I would run a regular BCG and a KAK flash can at 4.2oz
www.kakindustry.com/kak-industry-flash-can

You could also save some money with adding a little weight by using a MI or other hand guard

fuel fire desire
March 08, 2017, 14:18
One of the big costs in the rifle is the lower I already have, and upper I'm going to buy to match. I got a deal on the lower, but as a pair they're still going to be around $500. Not a lightweight set.... but are top quality with pretty neat machining and full ambi controls.

I basically jumped on a deal on a lower and this is the only AR build I haven't tried yet and has been on my mind.


The hand guard is a big cost too, and aside from its light weight....I really like the aesthetics of it being the same length as the barrel with cutouts on the sides for the comp.

This can be done cheaper, yes, but I'm also going for a bit of cool factor too.

The SLR adjustable block was exactly what I was thinking of if it was recommended I go that route. I've only ever used front sight blocks or pic rail blocks before, driving traditional BCG's on traditional buffers/ springs. So the entire adjustable block on an impingement gun is new to me.

Do they work the same as a FAL regulator but with an Allen key? Start with the gas set low and increase gas until running reliably?

CG&L
March 08, 2017, 15:07
Yes, any adj gas block will be set the same way. Load one round in the mag and shoot. Open screw until bolt locks back. After that, it's up to you if you want to go an extra click.

I don't know if you want the clamp type or the set screw type or if it matters.
I started using the set screw type because it's the one you can pin. If you decide to use the set screw type, you'll need a dimpler and the drill jig for the pin. It's a lot simpler to use the clamp type.

jhend170
March 08, 2017, 15:36
You may have to find an ammo brand or load you like and stick with it, tuning the gas to the load. Start going with lightweight components and they can get a bit finicky, but stay consistent in what you feed it and it should run fine.

fuel fire desire
March 08, 2017, 17:10
I don't see a reason why I should not go with an adjustable gas block. I might as well just opt for it. I was probably going to go for a clamp type, just for ease of installation. I don't have access to a drill press anymore.


The barrel choice I made was one of the lighter options available without going carbon, and it had decent reviews (claiming 1.5 MOA with M855). For some reason Faxon only offers their pencil barrel with a mid length gas system.

My train of thought with gassing this gun is that if I can reduce dwell time to compensate for less moving mass, its going to be more in the ballpark of what this rifle will require and can subsequently fine tune with an adjustable block. My other thought, is that the carbine gas system was originally designed for the M4 setup which was a 14.5" correct? It works well with full weight BCG's in 16" guns, erring on the side of over gassing to push through lack of lubricant or excessive dirt. Being that Im stepping outside of the norm for BCG mass, and factoring in the conditions this gun is going to be used in (immaculately clean), wouldn't a mid length gas system help prevent getting into a very over gassed situation? Would I be risking under gassing? (assuming Faxon did their job with drilling a proper port)

Im not trying to pose an argument/ counter argument....Im just throwing out my thought process on the subject so others can comment on the way I think the physics of this rifle works. IANAE

crcksht
March 08, 2017, 17:17
You can use a traditional gas block if you use one of these:
https://www.mgi-military.com/store/index.php?category=17

I modded a pistol length tube for a whisper build with one of their adjustable valves and it works great so the factory built tubes should be good to go as well. The only issue you may have is having to use a handguard where the holes line up with the location of the adjustment screw.

fuel fire desire
March 08, 2017, 17:27
You can use a traditional gas block if you use one of these:
https://www.mgi-military.com/store/index.php?category=17

I modded a pistol length tube for a whisper build with one of their adjustable valves and it works great so the factory built tubes should be good to go as well. The only issue you may have is having to use a handguard where the holes line up with the location of the adjustment screw.


I did not know these existed.....

If I'm lucky enough to have the adjustment hole line up with a key mod slot that looks like it would be the ticket.

I was figuring I would have to do all my gas adjustments with the hand guard off to be able to get to the gas block adjustment.

CG&L
March 08, 2017, 19:30
The SLR adjust from the front, there's no need to remove the handguard. It would be unusual for the hand guard to be so long as to not allow the use of the supplied allen wrench

I use the SLR on my 300 BLK builds. They have the pistol length gas system and some of them require a long handle allen wrenche.

Dwell time is determined by the distance from the gas port to the muzzle. Adding a suppressor will increase dwell time. A comp such a Flaming Pig or Barking Spider is supposed to make a difference and probably does to some degree

fuel fire desire
March 08, 2017, 20:50
The SLR adjust from the front, there's no need to remove the handguard. It would be unusual for the hand guard to be so long as to not allow the use of the supplied allen wrench

I use the SLR on my 300 BLK builds. They have the pistol length gas system and some of them require a long handle allen wrenche.

Dwell time is determined by the distance from the gas port to the muzzle. Adding a suppressor will increase dwell time. A comp such a Flaming Pig or Barking Spider is supposed to make a difference and probably does to some degree

Im planning on using a 16.5" Vella Trident hand guard on a 16" barrel with a M4-72 brake, which are 2.5" long. So that gas port would be buried deep under that hand guard by 7.5". Only the last 2" (the baffle section) of that comp should be poking out.


Same hand guard....but not a M4-72.
http://i.imgur.com/55WbFzq.jpg?fb



No suppressor in the future for this gun. The most it will get is that M4-72, and a blast shield for busy range days.



The more I look at the topside of that hand guard though, the more I think the relief cuts will be large enough to fit a hex key in to reach the block. So the fancy tube might just be a moot point.

CG&L
March 08, 2017, 21:39
That's still no problem with the SLR. They make 3 long handled Allen wrenches, a 5", 8" and a 13"
http://slrrifleworks.com/index.php?route=product/product&path=57_129&product_id=94

I have both the 8" and 13"

It'll slip right through with no problem whatsoever. A 300BLK has a pistol-length gas port and I use long handguards.
The adjustment screw is in front of the gas block on the SLR

fuel fire desire
March 08, 2017, 23:23
That's still no problem with the SLR. They make 3 long handled Allen wrenches, a 5", 8" and a 13"
http://slrrifleworks.com/index.php?route=product/product&path=57_129&product_id=94

I have both the 8" and 13"

It'll slip right through with no problem whatsoever. A 300BLK has a pistol-length gas port and I use long handguards.
The adjustment screw is in front of the gas block on the SLR


Perfect.



Just curious.....but how does the SLR work? I understand the screw does not directly block gas flow. Is it exhausting gas like a FAL regulator?

http://www.tacticallink.com/assets/images/productimages/slrrifleworks/gasblocks/sentry7/slr-sentry7-clamp.jpg

hueyville
March 09, 2017, 02:19
Curly/Pig Tail gas tube increases carbine gas length to rifle. I fix a lot of superlight builds for people but they usually gain weight in process. Can make them work but reliability is more important than weight to me. Whats a pound between friends?

CG&L
March 09, 2017, 10:45
The SLR doesn't vent, it blocks the gas hole

The hole you see on top isn't a vent hole, it's the hole where you pin the gas tube

The flat piece of metal you see on the side is a leaf spring. The screw is squared off past the threads. This is the detent action for the adjustment

Most adjustable gas blocks has a small coil spring for the detent. SLR uses a leaf spring

You may very well end up not liking the SLR for some reason but I like them.
They're on all of my personal ARs and I use them on all of the custom ARs I've built for my customers

fuel fire desire
March 09, 2017, 13:09
The SLR doesn't vent, it blocks the gas hole

The hole you see on top isn't a vent hole, it's the hole where you pin the gas tube

The flat piece of metal you see on the side is a leaf spring. The screw is squared off past the threads. This is the detent action for the adjustment

Most adjustable gas blocks has a small coil spring for the detent. SLR uses a leaf spring

You may very well end up not liking the SLR for some reason but I like them.
They're on all of my personal ARs and I use them on all of the custom ARs I've built for my customers


I have to be thinking of the Superlative Arms then. Got it.


...all the articles and descriptions Ive been reading are starting to merge together, lol.

hueyville
March 09, 2017, 18:12
Nothing about this is a lightweight AR but 22 Nosler burning 25% more powder behind a Barnes Copper Solid or 50 grain ballistic tip is going to be interesting tomorrow. Not final scope or mount but will get me to range and idea of how it shoots.

http://i63.tinypic.com/2z88028.jpg

MistWolf
March 10, 2017, 03:49
It's false economy to try to save weight in the reciprocating mass only to add a useless 5 oz blast shield at the muzzle. It does no good to shave weight where it's needed only to add where it's not.

For an AR to operate reliably, it needs a certain amount of reciprocating mass travelling at a certain speed. Decrease the mass without increasing speed and there will be a loss of momentum. You can try to make up by increasing speed but too much speed causes problems with bolt bounce.

My advice is to get rid of the heavy blast shield thingy, use an A2 birdacage instead of a muzzle brake and run a full weight carrier and the proper weight buffer. That blast shield adds as much as 18 inch/pounds to the moment of the rifle

The Wolf Pup is equipped with an SLR gas block
http://i115.photobucket.com/albums/n289/SgtSongDog/Lil%20Wolf%20Pup/Silent%20Wolf_zpssvjbckoe.jpg

It's a good choice.

The Superlative Arms gas block give you the choice of working by venting gas, or by blocking gas flow

hueyville
March 10, 2017, 04:34
I can't endorse this adjustible gas tube but guy I trust a lot says he uses on every build and never had an issue. At $59 and looks easy to adjust is not very expensive when leaves a person open to use any block they want. Have two mid, two rifle and one carbine length on way.

https://www.mgi-military.com/image_upload/Gas%20Tube-Mid.jpg

For carbine gas plan to use curly tube and adjustible block for lengthening gas system. Like option of having the longer system even if close off any gas or not. These people have a lot of imteresting stuff like lowers can swap mag well front section to AR, AK or 9mm pistol magwell. Swap barrel rifles with a dozen caliber options in one package. The tubes are about only thing they sell I can afford.

https://www.mgi-military.com/store/index.php?category=17

MistWolf
March 10, 2017, 05:12
That "curly que" gas tube is useless. It makes the path the gas travels longer, but it does nothing to change pressure or flow

hueyville
March 10, 2017, 05:27
That "curly que" gas tube is useless. It makes the path the gas travels longer, but it does nothing to change pressure or flow

Dang, chemistry was a while back but believe one of the gas laws says an equal volume of gas in larger container will have less pressure. Science geek please step in here please. Bullet passes gas port and dwell time of bullet to muzzle is same. If gas system is longer then fixed amount of gas is occupying larger area thus pressure would be reduced. How much, so far from higher math calculating the volume of a gas tube is not something can do from memory and not using Google to try and look smarter. Killed all those brain cells on purpose.

Timber Wolf
March 10, 2017, 08:51
That "curly que" gas tube is useless. It makes the path the gas travels longer, but it does nothing to change pressure or flow

I don't know much, except I bought a no-count non-functioning CAR (really cheap, less than parts value) that I "fixed" by replacing the pig-tail gas tube with a standard carbine length tube. Runs fine now.:)

MistWolf
March 10, 2017, 14:10
Increasing volume decreases pressure in a closed, static system, but things are more complicated than that in a dynamic, open system. The flow from the barrel is still more than enough to keep the gasses at peak pressure, even with the small increase in volume of the curly que gas tube and flow rate will remain unchanged

hueyville
March 10, 2017, 15:29
May be the placebo effect but use them all the time, often in rifles have fired with stock carbine tube and rifles to cycle a little slower though a buffer change, and sometimes a spring swap, usually accompanies the curly tube. Have used on problem uppers that were no longer problems after and never had a rifle fail to function flawlessly after adding.

Bought an oddball 18" barrel with carbine gas. Thing was harsh even with a spring change and heavy buffer. Did the buffer and spring at range and best groups of the day with said rifle were all hovering around 1 MOA. Before next range trip added a curly tube and nothing else. Rifle was shooting 3/4 MOA next trip out with same ammo and same shooter but could have been conditions or any number of things. Any parts change affects fitment of the parts it attaches to. They really don't cost much, they make me "feel" better and rifle "feels" a tad better but could again be the placebo or some N.Y. Times liberalism infecting my feelings.

Know several people that are of same opinion that assemble a lot of uppers. I assemble or repair an upper on average of once or twice a week. All pistol length and most carbine length gas get one and never had a gun throw an issue due to it. Could see one that got dinged or not installed properly causing an issue but don't see any way if done right can hurt the rifle.

Built a few SlideFire rifles when trip across a deal on stock and its as cheap or cheaper than a milspec carbine setup. One adventure purchased three N.I.B. and sold one to a friend. Built two blem Anderson receiver sets with curly tube and H2 buffer which ran perfect. Friend put his on a stock Smith M&P 15 and had issues getting it to bump fire. Put a curly tube on his upper, handed him a H2 buffer and next trip to range rifle bumped perfectly. Was it the tube, buffer or combination of two? Dunno, just never had a rifle run worse and most seem better so buy them six at a time. All five of my carbine length 6.8's have one and none have had a failure to feed. fire or extract from first trip to range and on down the road. Who knows, when the first lot of adjustable gas tubes arrives they may end up on every rifle that would have gotten a curly before.

MistWolf
March 10, 2017, 17:47
Making more than one change at a time isn't a good way to evaluate how a single change affected the rifle. One way to test the curly que tube would be to install it on an AR with an adjustable gas block. Then test to see how many clicks it takes to get the AR to lock back with the curly que compared to a standard gas tube.

The curl does help absorb shock from the flow and allow the tube to flex. That's why various pneumatic/hydraulic systems have curled tubes in some places.

I find that when tuning an AR, it's best to start with a known baseline for the reciprocating mass and spring rate- that is, to start with a carrier and buffer weight and appropriate spring- and match the gas flow to match

fuel fire desire
March 10, 2017, 17:48
It's false economy to try to save weight in the reciprocating mass only to add a useless 5 oz blast shield at the muzzle. It does no good to shave weight where it's needed only to add where it's not.





The shield was QD and for busy range days, as to not be 'that guy' in the next stall with an obnoxious brake. I already don't shoot my braked .308 if I can't be at least 4 stalls down from the next person as a courtesy. The 5.4oz was entirely removable and attached to A2 style mounts, which the M4-72 had. BUT.......it's a moot point, since the OD of the shield is larger than the ID of the hand guard I'm using. So it's not going on anyway.


I'm choosing the M4-72 because back when I was doing research for brakes on my DSA, it kept popping up as the most effective with the people running scientific comparisons. The reason I ended up with the M11 on the DSA, is while it was slightly less effective at reducing recoil, many claimed it was noticeably less obnoxious. I've been very happy with their product.

MistWolf
March 10, 2017, 17:52
I knew why you wanted a blast shield. I'm just pointing out that using an A2 birdcage instead of a brake and a blast shield is a better way to avoid being "that guy"

fuel fire desire
March 10, 2017, 18:55
I knew why you wanted a blast shield. I'm just pointing out that using an A2 birdcage instead of a brake and a blast shield is a better way to avoid being "that guy"

Gotcha.


I've actually never shot a 5.56 with anything other than a A2 cage. But I've been so thoroughly impressed with how well the Precision Armament works on the DSA, I'd love to see how little recoil I'd get out of an already light recoiling rifle. I'm actually excited to see what this low mass, adjustable gas, brake setup will yield......and I guess continue to be "that guy" lol.

hueyville
March 11, 2017, 10:26
Have put brakes on several personal 5.56 and 6.8 spc II AR 15's run for extended time, as in over a year, then swap to flash hider that accepts suppressors and from shooters end no real difference in felt recoil or muzzle climb noticed. Did make people at range happier when no can. If weight is issue seen standard flash hider in aluminum and titanium that weigh almost nothing.

On your trigger selection a one piece drop in trigger is not user serviceable in most cases. Anything goes hinky and either have a complete replacement trigger or your rifle is a stick. Below is the trigger put in my 22 Nosler build. It is a free take out from a S&W M&P 15. Totally milspec and totally serviceable with common parts. Put in lower with OEM springs (I use a Brownell trigger jig) cover engagement areas with old fashioned Crest toothpaste or fine lapping compound of choice and cycle about 30 to 50 times. Remove from rifle or jig, clean very well, clean again and reassemble with JP Enhanced Reliability Spring kit 3.5 or 4.0 version. Used the 3.5 and without putting in my hammer and sear jig or doing anything special came out at 3.3 pounds. Has a little creep and no travel. Feels like most $200 two stage triggers and have exactly $9.95 in it plus squirt of toothpaste.

http://i63.tinypic.com/2uq0yzs.jpg

http://i63.tinypic.com/n3nj9y.jpg

If anything goes wrong down the road can replace any spring or part on the fly with contents of spare parts kit that goes everywhere I do just like first aid kit. Yep, weighs maybe half ounce more but utterly reliable and if lightning struck can fix it. Have three one piece triggers with broken internals people have given me. Someday plan to do autopsies on them. If your rifle will ever be pressed into defensive situation a 6.3 pound rifle that doesn't break is better than a 5.9 pound stick. Load magazines to 28 instead of 30 rounds and makes up difference. That's one of my pet peeves with saving a few ounces on a build, Use 55 grain ammo instead of 62 and 30 rounds time six spare magazines has made a bigger difference. Or buy 40 grain varmint bullets, what use in house so don't have shoot throughs and round leave room, house and into a neighbors. Bet a sub six pound can be built using mostly standard parts. In fact know it can as have a few, started on billet magnesium receivers, used light profile 14.7" barrels and all else was standard parts unless optics added more than a small pistol size red dot.

fuel fire desire
March 11, 2017, 14:21
I have been very lucky with LPK's in the past, where they are crisp out of the box with little pre travel or creep. That said, I've handled some off the shelf AR's that felt just plain bad. Since my goal for this rifle was to essentially fill the role a Caterham does next to a Wrangler in the same garage (my SA58), I decided to go the easy route to getting a neat-o feeling trigger.

I was originally looking at the ELF, as it has been claimed to have no measurable take up or creep with a VERY positive reset....but ultimately shied away from it for its cost. Aside from having the trigger shoe I was looking for (flat with a bottom notch to index on), the CMC showed to have very little pre or over travel with a "near glass rod" break (referencing the article 'Drop In Trigger Roundup'). The final reason I decided upon it, in addition to its reviewed stats and shoe, was I stumbled upon one on a flash clearance for $100.

I understand it's essentially a sealed unit, and being a 'race' part in a 'race' gun it will not have the life, reliability, or drop safety if a mil-spec or even performance LPK group.

With all that said, if it comes down to this being used as a defensive carbine over my "combat oriented" and "ready standby" SA58....... either I'm in desperate doo doo and it's in the trunk of my car on range day when SHTF, or I'm handing it off to a friend to fight with me, in which case I'm in deep deep doo doo. In the highly unlikely situation I'd have that CMC fail in combat within the scenario where I was unable to access my 'grab n go' DSA, WITHIN the need to fight with a carbine.........either I'm standing shoulder to shoulder with Rick Grimes...or I'm dead/ soon to be dead already.



ANYWAY... tldr:

I went with a drop in to get instant performance so I would have to do less work myself.


If it's a sunny beautiful day, I'll take the Caterham out for a few laps around the block, but if I ever need to take that nasty ragged Jeep trail in horrible conditions....I'll bear the weight of the 10+ pound FAL.

hueyville
March 11, 2017, 17:04
One of the best articles have seen reviewing 13 different drop in trigger groups. Almost a must read on the subject.

http://www.thetruthaboutguns.com/2016/04/jeremy-s/ar-15-drop-in-trigger-roundup/

fuel fire desire
March 11, 2017, 19:23
One of the best articles have seen reviewing 13 different drop in trigger groups. Almost a must read on the subject.

http://www.thetruthaboutguns.com/2016/04/jeremy-s/ar-15-drop-in-trigger-roundup/

That's exactly what I started my research with. Great article.

fuel fire desire
March 14, 2017, 21:17
Lower parts are in, and it feels like christmas.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/Santan2_zpstn1aa1kx.jpg



Everything went together easy like I was expecting. The biggest worry I had was the CMC fitting with play in the trigger, since theres no tension system with this drop in. Laterally its solid, transversely it has just a hint of wobble, but its not felt unless you pinch the trigger shoe and try to move it side to side. It takes a bit of force for it to move, and it doesn't wobble on its own or under normal trigger pressure. Its pull is smooth, with no take up, but there is creep. Its not felt unless its being pulled very slowly while actively looking for creep since its not much, and the weight drops off the further into the pull you go.....and that hides it. Under a normal press, it does have that smooth glass-like break. The shoe sits further forward compared to a standard LPK, which is perfect for my large hands. Comfortable, predictable, and Im sure quite fast. Worth my $100.

http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/santan6_zpsmfkmsxtd.jpg


The Ace stock went together easy, but not how I expected. It came with a cap on the end of the tube that I thought was part of the butt plate attachment system, but its not. The tube threads into the receiver, a clamp goes on where the traditional end plate would go to keep it from unthreading, foam goes over the tube, and the butt plate clamps on to the tube. Super easy. The instructions were vague, and all I can figure that cap was for is to add another 1" to the LOP. Combined with the rubber pad, that gives 2" of adjustment to total LOP. Not bad. I added the rubber pad, but left the cap/ spacer off. The aluminum butt plate has a waffle pattern cast into it, so the rubber isnt required, but its a super soft tacky rubber that helps keep it planted.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/santan1_zpsxukvt7tg.jpg

2336
March 14, 2017, 23:58
I don't see a reason why I should not go with an adjustable gas block. I might as well just opt for it. I was probably going to go for a clamp type, just for ease of installation. I don't have access to a drill press anymore.


The barrel choice I made was one of the lighter options available without going carbon, and it had decent reviews (claiming 1.5 MOA with M855). For some reason Faxon only offers their pencil barrel with a mid length gas system.

My train of thought with gassing this gun is that if I can reduce dwell time to compensate for less moving mass, its going to be more in the ballpark of what this rifle will require and can subsequently fine tune with an adjustable block. My other thought, is that the carbine gas system was originally designed for the M4 setup which was a 14.5" correct? It works well with full weight BCG's in 16" guns, erring on the side of over gassing to push through lack of lubricant or excessive dirt. Being that Im stepping outside of the norm for BCG mass, and factoring in the conditions this gun is going to be used in (immaculately clean), wouldn't a mid length gas system help prevent getting into a very over gassed situation? Would I be risking under gassing? (assuming Faxon did their job with drilling a proper port)

Im not trying to pose an argument/ counter argument....Im just throwing out my thought process on the subject so others can comment on the way I think the physics of this rifle works. IANAE

Just my two cents worth. I built a lightweight carbine using a 16" Gunner profile barrel (mid-length gas) and am very pleased with it. I'm using a standard M16A1 BCG, nothing special and an H2 buffer, inside a Cerro Forge flat-top upper with BUIS - no red dot yet. Runs just fine, never have had any FTF, FTE - no problems whatsoever. And the rifle weighs a shade over 5 lbs. The Faxon barrel has netted me way less than 1 MOA accuracy! This Faxon barrel is the third one I've used - buy Faxon with confidence! Great products and excellent customer service!

fuel fire desire
March 15, 2017, 11:24
Just my two cents worth. I built a lightweight carbine using a 16" Gunner profile barrel (mid-length gas) and am very pleased with it. I'm using a standard M16A1 BCG, nothing special and an H2 buffer, inside a Cerro Forge flat-top upper with BUIS - no red dot yet. Runs just fine, never have had any FTF, FTE - no problems whatsoever. And the rifle weighs a shade over 5 lbs. The Faxon barrel has netted me way less than 1 MOA accuracy! This Faxon barrel is the third one I've used - buy Faxon with confidence! Great products and excellent customer service!

That's great to hear. I had not bought anything from them before.

I ordered the barrel last week, and will brobably order their lightweight BCG in the next week or two.

fuel fire desire
March 16, 2017, 12:08
A thought just came to me...... Head spacing.



I have a vague understanding that adjusting the head spacing on an AR requires reaming the chamber or lathing threads off the receiver, but how important is it (or rather how many of you) actually check head spacing on an AR with a go/ no-go on a casual parts bin build?

Is it worth buying a set of go/ no-go gauges? (I know...better safe than sorry etc.). Both the bolt, BCG, and barrel are from the same reputable company, and the upper is a high end billet (not just a $50 anderson). Even if I found an issue, I could do nothing about it without the assistance of a shop.

hueyville
March 16, 2017, 12:22
Barrel has no headspacing issues 99.9% of time if extension if factory installed with milspec bolt. Exceptions are some of the ARP and JP enhanced or reinforced bolts that won't close on most milspec extensions. That said, will recommend all builders show a new rifle the go/no go gauges anyway. If doing a one time build borrow them. I will mail you a set if return when finished.

hueyville
March 17, 2017, 20:51
Been thinking about building a lightweight AR 15 in racing bike terms. Pay $25 to $50 per gram to save weight using titanium and carbon fiber. Went to DSA and looked at their titanium parts.

Put a kit in my cart. Titanium Flash Hider, Ultralight Gas Block, Buffer Tube Lock Ring, Hammer/Trigger Pins, Takedown & Pivot Pin Set (divoted lightest set), Forward Assist Kit, Buffer Retainer Plunger, Pistol Grip Retaining Screw, Titanium Firing Pin all totalled $278. Have not figured weight savings but most are half or more than half the weight of steel. Seen several carbon fiber forearms that are paper light.

If used these in conjunction with one of the billet magnesium receiver sets and DS enhanced lightweight titanium parts collapsible stock and some other parts have handled with a 14.7" light profile barrel bet a five pound AR can be built. While senseless, have the billet magnesium upper and lower receivers, carbon fiber handguard plus the titanium parts are in my cart and may push the buy button. Have seen super lightweight pistol grips so out of being to cool kid on the block and having a rifle that weighs what some of my pistols do putting project officially on backburner.

fuel fire desire
March 18, 2017, 16:45
I appreciate the offer on the gauges!

I have this same thread running on a local board too, with another offer from someone on the other side of town.


I'm not sure when exactly I'd be able to test it though, as everyone seems to be out of the 16.5" Trident....even Vella direct. That's the last component I have to order.



I did get lucky and found a Sig Romeo3 on sale for $100 off. I think that's about the lightest optic that can co witness that's out now.


I can't find a total weight anywhere, but weight without mount is 1.4oz, and that mount looks pretty light.

EDIT:

HERES A WRITE UP ON THE ROMEO3 (http://www.falfiles.com/forums/showthread.php?t=412575)

fuel fire desire
April 07, 2017, 22:34
I was getting rather worried about getting my hand guard in. Apparently its out of stock everywhere, and backordered from the manufacturer. I found a too-good-to-be-true online store that I had not heard of before that had them listed as "in stock" and for $50 below every other store. I placed my order weeks ago.....and heard nothing from them. Multiple phone calls, emails......and no response. They took my money, but the status of my order on the website stayed at "pending" over the last few weeks. I was planning on giving the store one more email before calling my credit card company next week, but.....IT SHOWED UP!




So now I have all the components. I still need to get ahold of a 1-1/4" crows foot to torque the barrel nut down (I have a wrench, crows foot on order), but I at least got a chance to mock it all up to get a feel for its balance.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/C3EDBBEE-EFCD-4128-9DDC-02B7F84CA7BC_zpsrxvgzyfl.jpg


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/5D38B177-065C-471F-9776-449595ED6039_zpsly7h0l2g.jpg


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/F7A44773-22AA-402C-8940-B77676737104_zpsd6zla0be.jpg


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/0410B07B-5579-47FC-8F75-5F349C468EF2_zpscv6i3dyu.jpg


Aesthetically its exactly what I was looking for. The hand guard ends just shy of the baffles on the comp, and the red charging handle breaks up the monotone black just enough to be interesting without being obtuse IMO.


Its not as "shockingly" light as I had hoped, and I think a lot of that is the illusion of weight given by that big heavy comp on the end of the barrel. With it off, it feels MUCH lighter, so its just a perceived weight issue from the over all balance of the rifle. Its still a well balanced 5.5 pound AR with optic that points quickly and instinctively, so Im pleased.

Final assembly and tuning to go.

hueyville
April 08, 2017, 10:16
If ordered your barrel nut tool, good move, need to have correct tool for the job for future maintenance. Same as with the go/no-go gauges have one that don't use too often (yesterday needed it on a "free" upper fix) that will mail along with the gauges. Use all the tools, when finished mail back. You only pay postage one direction. Have AR tools all over the county and country since over years have upgraded, bought doubles when saw a sale, etc. Yesterday LGS asked to borrow two specialty tools when stopped to pick up my AR 15 milling fixture had loaned them. Have to do some custom cuts in a pick rail to fit a set of tall pistol sights on top of the Flaming Pig build which will be visible through the C More and save the set ordered that cowitness with C More for next pig build as plan to use another C More on it then scope the third.

Please I need help and an intervention from my family won't fix my addiction. Afraid may find something more expensive than poodle shooters and 1911's to fixate on. Have promised myself no more FAL kits when four left are done. My promise to wife is hear on out only trade up on FAL's, increase quality rather than increase numbers. L1a1's and especially a decent L2a1 is exempt from FAL as don't even share same names or measurement systems. Very nice looking rifle. Just received two of the SIG full length fixed carbon fiber stocks. So pleased ordering a third today while available cheap.

fuel fire desire
April 10, 2017, 18:47
Started final assembly today. The big hold up I have is the accu-washer kit I had from another build was for a .308, and is way too large for this 5.56. I had completely glazed over that fact. So I still need to order more parts to get the comp on.


The reaction rod was a huge help in assembly. I had no fear of damaging the receiver, especially with the multiple attempts at torquing that was needed with this particular nut. The small threaded holes had to be square to the receiver, and the kit came with three foil shims to help align them under torque. I used white lithium grease on the nut (recommended by the manufacturer). Everything seems to have gone together alright. Recommended torque was 30-80 ft/lbs, I got it to 40.

http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/2E231A06-7DE1-4C1A-9E36-39A571C26453_zpsrnamcsxo.jpg

http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/C5FD7A5B-4519-4168-ABDE-71E12865A5BA_zpsjckqx9q6.jpg


The hand guard kit was one precision machined unit. There was absolutely no slop in sliding the guard over the nut, and it docks absolutely flush to the receiver. The barrel extension and feed ramps mate PERFECTLY to the receiver. Its such a precise fit, I can drag my fingernail across the inside of the receiver and not feel where the barrel extension ends and the receiver begins. That just blows me away, especially on parts made by two different manufacturers.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/19053F34-A125-44D3-91BB-4ED7DE846860_zpsqotdf3jg.jpg


The gas system disappears under the hand guard with the black block and tube. I am so happy I found a black tube to match everything. I was hunting for a red one to accent the red charging handle, but I think that would have pushed the appearance of the rifle just over the gaudy threshold. I still cant get over the level of precision and quality all of these parts have, especially as a finished assembly. I definitely got what I paid for.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/3EEF8215-F3C1-42CC-AF95-F4CD2F4FAA08_zpsvh5yqzvj.jpg

http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/C6AE3067-4424-4FDF-9E4A-09E3F7BD3FEC_zpsuuvzym1w.jpg

Before I get the headspace checked on it Im going to finish final assembly. I still need an Accu-washer kit to torque the comp down, and then the hand guard after it. Im also going to go for a low mass buffer kit with reduced power spring that was recommended by someone on another board.

https://taccom3g.com/product/rifle-recoil-system/

It looks like that saves me 3.4 ounces overall, and 4.5 ounces in moving mass. Incredible.

That will get total wight of the rifle under 5 pounds (without optic). 79.5 ounces

Its almost fun time.....almost.....

fuel fire desire
April 24, 2017, 21:39
I finally received the Go/No-Go gages and gas block tool, so today was test and tune day!


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/5C6A182E-0522-4E41-9FEB-87A20D471723_zps6r0ehsta.jpg


I am simply stunned as to the performance of this rifle. With no exaggeration, it recoils like a 10/22. Letting it sit on a bag, stock hanging in the air, lightly squeezing the trigger yields about one inch of rearward movement. When shouldered no recoil, muzzle climb, or muscle dip is felt at all. It reminds me of the kind of "recoil" my old paintball gun gave me 15 years ago.



The one thing I was not expecting though, was how BRUTAL the concussion is with this brake. Not only does it feel like a slap in the face, but the pressure imbalance within my sinuses gives me a feeling similar to that when you knock your head hard on a low hanging wood beam unexpectedly. Ive never felt such a thing with a 5.56....or even big bores before. My braked 16" DSA has nothing on this gun for rearward concussion.

http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/3C24F18F-11F0-4567-8AB1-121725A908A1_zps7mjpeueb.png



The gas venting off of the brake comes right back at you too. Straight down both arms and into my face. Not uncomfortable, but something I was not expecting. This is what my hand looked like after about 80 rounds free handing the rifle like in the above pic. The M4-72 is one hell of a brake.


http://i129.photobucket.com/albums/p205/fuel_fire_desirels1/firearms/0269F825-1B54-4C10-B194-99D2F40350D8_zpsbfncwraf.jpg




I set out to build a sub 6 lb AR with minimal recoil, and got one just under 5 pounds with ZERO muzzle movement even with minimal support. Mag dumps while transitioning between a 25 and 100 yard target yielded all rounds on paper. THOROUGHLY impressed with this build.

hueyville
May 12, 2017, 09:32
For those of you with overgassing issues and suppressors, have now tested two of these hard and did so well just got this first care package. Website says out of stock but if call they have plenty and be sure to tell them the "hillbilly" recomended their product. More people I send, better they treat me. Not trying to be a salesman but sharing some products that work well.

http://i65.tinypic.com/2urxaut.jpg

http://i65.tinypic.com/2ur8lg0.jpg

These are especially great on builds with OEM handguards as can just stick Allen wrench through a hole and tune your rifle. Have run two SBR's hard with these. One has had a binary trigger for a while and second got one a couple weeks ago. Taking an SBR and running mag dumps with a bin are is tough on a rifle. Also in one of the rifles have an MGI Rate Reduction Buffer with their extractor D-ring in bolt. Here is theor little Q and A about the device.


Q:***What is the approximate number of rounds per minute with both rifle and carbine models?
A:***Our Rate & Recoil Reducing Buffer is self adjusting. In general this means that the more you need it the more it does. As an example of this, in recent test with two of our demo guns, we received the following results. The 11 1/2 inch barreled carbine was initially firing 1016 rounds per minute (rpm). After installing the MGI Buffer, the rate of fire dropped 271 rpm to a rate of 745 rpm. Our 20 inch barreled demo gun was initially shooting at a rate of 771 rpm. After installing the MGI Buffer the rate of fire fell 133 rpm to a rate of 638 rpm.*

Q:***There should be a caliber rating for these buffers?
A:** The MGI Rate & Recoil Reducing Buffer, was designed to work not only in the standard M4 / M16 / AR-15 platforms, but also with MGI's Modular Weapon System (Hydra). Because of the basic mechanical function of the buffer, it works very well with all of the calibers you mentioned. Basically, the harder you push it, the harder it pushes back to counter the recoil. It's function is similar in nature to that of placing a hammer in each of your hands and swinging them towards each other meeting in front of you. When they meet, they will cancel out the energy in each other coming to a stop. If you swing both hammers harder, they will cancel out each other's forward momentum. This is the same as the carrier moving to the rear as the buffer weights are moving forward to help cancel out the rearward energy of the carrier. Changing to a larger caliber just causes the weights to be hitting the carrier that much harder.

People are always complaining about the hammer following bolt and other issues that get with binary triggers. My first Franklin was a Gen II that they soon said had to swap buffer spring and buy their expensive bolt carrier to reduce issues. Already had the MGI tube in the SBR with welded can but rather than buy the expensive bolt and spring added this buffer with the Tubbs Flatwire spring in the rifle and it runs flawlessly once gas was adjusted. Have now had a hammer follow issue once with the new Gen III binary telling me will see more if don't get ahead of it so have another rate reduction buffer on the way. My cousin dropped one in one of his select fire M16A2's and said will be adding to all of them. Says it calmed it down to point is smooth as butter. Just dropping 100 rpm or so and getting gas tweaked makes quick gun 90% more reliable.

MGI adjustable gas tube view from above rifle:

http://i65.tinypic.com/qnqp80.jpg

Pulled rifle for this picture from vault and figured would carry as extra truck rifle today. can see how easy to access adjustment screw is, much easier than chasing a lot of low profile adjustable gas blocks under a freefloat hand guard. Actually second redundant long gun backup. Have a 6.8 behind the seat that takes a multi-caliber quick change can, a 22 Nosler in case see a ground hog or crow in the distance (farmers are planting and their wife will bake you a pie if kill crows eating the fresh corn seedlings) and the newer 5.56 one stamp binary trigger AR 15. Keep copies of all BATFE forms in brief case so no matter what might carry, have correct form in the truck. Keep a sharp eye on the briefcase as has a SIG 9mm with Osprey can in the bottom 24/7/365. If were to have to defend myself, if have time or anticipate it will reach in briefcase and grab the SIG just inside rather than the SIG on my belt as it doesn't bust ear drums though if have that much time can grab the Sonic II earplugs from console. Wear them as part of regular day if working in the hood.

Edit to the last of OP's post:
Have a PRI Quiet Control Brake on the 22 Nosler in truck with 18" barrel. Not only does it work very well, it has lowest sound signature at operators end of any 5.56 brake have used personally. Did try it on a 5.56 Wylde before the Nosler just to see how it acted for comparison. Others at the range say its less oppressive than most 5.56 NATO rifles with brakes if off to the side and the Nosler is burning 25% more powder.

http://www.precisionreflex.com/Detail.aspx?PROD=186715

hueyville
May 14, 2017, 18:27
Installed first test unit of MGI adjustible gas tubes beginning of this thread. Used it in the single stamp SBR with Gen II Franklin binary trigger, Tubbs Flatwire buffer spring and MGI Rate Reduction Buffer. Between the buffer and tube got the #1 one stamp SBR running perfect. When the others arrived threw one on #2 one stamp SBR, swapped the Slash heavy buffer for an H2 building a new lower using a Mag Tactical lower and a Gen III Franklin binary trigger with provided buffer spring. Friend who worked with me today wanted to run some AR's while out and had a perfect place to play, 400 acre tract with over a mile of timber before anything of consequence. Took both the one stamps, Flaming Pig with other Gen III binary, curly gas, the Slash Heavy Buffer and supplied buffer spring. Also a pair of 14.7" 6.8's with only enough rounds to set gas and optics run till today. Ran the 6.8's with multi-caliber quick change cans.

Guessed gas setting on rebuild of the #2 one stamp and didn't adjust gas on either of the 6.8's using pair of AAC 762SDN-6's. Ran all the guns hard as possible. Buddy had never used a binary and had some learning curve, I ran them all harder than ever had for extended period of time. Took 24 mags of 5.56 loaded 25 rounds each and 12 mags of 6.8 loaded 20 rounds each plus some odd ammo choices. All the 5.56 was fired through binary triggers with a few singles to verify optics then alternated doubles, bursts and mag dumps. 600 rounds of 55 and 62 grain bullets were sent down range in super fast fashion through three different setups and two generations of Franklin binaries without a single failure to feed, fire, extract, hammer following bolt or bolt running over hammer.

Also ran 20 rounds of 40 grain varmint bullets, 20 rounds of 69 grain SMK's and 20 rounds of 77 grain SMK's through the three binaries selected at random. Even trying to trip them up with the 40 grain and 77 grain bullets all ran perfect in single, double and raped ape speed. Ran mostly 90 grain Gold Dots through the 6.8's but did run a couple mags of 110 and 120 grain ammo to see if they would bend rims of cases without changing gas settings. All brass looked fine. Amazing how fast two people can run through 1,000 rounds of ammo with most of it in binary. Having all mags loaded and organized helped as well. Friend has left and now have to get back in the shop a few minutes to make up for two hour shooting break. Now have total trust in the binary triggers but will have Rate Reduction Buffers in the other two soon as they get here. The rifle with this device was the calmest of all and wanted to run.

Very pleased and had pair neighbors to property (knew we were coming and be shooting) come over who were stunned when told them none were select fire weapons. Explained binary and it's legal status but the price tag and big pile of empties looked way too expensive for their tastes. If paid retail instead of home rolled the ammo cost would make the binaries less fun. May even run the 1911 and the SIG 9mm before go home as already have cans on and didn't take time to shoot them. Bet if had been pulled over while on trip four suppressed AR's, three AR's with three position triggers and two pistols with cans would have gotten backup called while sorted through all the stamps. Gotta love America some days...

fuel fire desire
August 18, 2017, 15:29
The plot thickens..... the charging handle moves while firing. The bolt does not strike it. The gun is not over gassed. The latch holds strong when tugging on the handle.

I finally had a chance to take it out again. Different ammo, regassed the gun, same issue. The charging handle even jumped with the gas system OFF.

I took some slow mo video with my iPhone to see the sequence of events. It surprised me.

1. Trigger is pulled
2. Gun fires
3. Charging handle latch moves completely to its rearmost position
4. Charging handle begins to move backward
5. Bolt unlocks and begins to move
6. Charging handle moves rearward and stops on its own at 1.5" rearward, moving independent of bolt
7. Bolt reaches rear most position of travel (does not strike buffer)
8. Bolt moves forward, catching charging handle and sliding both home.


I put my thumb behind the charging handle while firing. It hit my thumb with almost no force, even just 1mm behind the closed position. It did not move my thumb.

Here are stills from the video....


These first two are with the gas system completely OFF. No bolt movement.

Gun at rest, charging handle fully latched at home.

https://i.imgur.com/v3N98UY.jpg


One frame after firing, before recoil impulse moves rifle rearward, charging handle latch moves to its rear most position, striking its stop. Charging handle just starting to move rearward. (It only takes 1/4 the distance the latch has moved in this photo to unlatch the handle.)

https://i.imgur.com/rx8bP2d.jpg




Another post coming with more images....

fuel fire desire
August 18, 2017, 15:33
This is with the rifle properly gassed. Bolt does not strike the buffer stop, but reverses direction on its own and catches the hold open.


Rifle at rest.

https://i.imgur.com/lOHgx2w.jpg


Immediately after firing. Bolt is still locked and closed, charging handle latch unlocked, charging handle beginning to move.


https://i.imgur.com/dVIF9Lq.jpg


Charging handle moving rearward. Bolt now unlocked and moving rearward.

https://i.imgur.com/etp93Vf.jpg



Bolt and charging handle moving freely rearward. Bolt moving 4x's the speed of the charging handle.

https://i.imgur.com/bmMSCYO.jpg



Bolt nearing its rearmost position, ejecting brass. Charging handle still moving rearward.

https://i.imgur.com/IHB0MLu.jpg



Rifle at rest. Bolt locked open, charging handle resting where it lies 1.5" aft of home.

https://i.imgur.com/6P1wYdu.jpg







My thought is to change out the handle for a different one......but looking at the way it's acting I'm afraid any other extended latch handle might act the same way. Thoughts?

jhend170
August 21, 2017, 15:53
My pistol is a SanTan. As a lefty I LOVE that lower! To keep mine lighter though I went with a standard mil-spec DD upper, but I'm sure it's only a few oz diff. Anyway it's good quality stuff.

As far as the moving CH goes... is there an unusual amount of crap inside the upper? Wondering if you have a lot of gas leaking internally and possibly blowing it backward. Another possibility is the CH is bent slightly. It can catch on the gas key and be drug back as the bolt cycles. In any case I'd be looking for wear marks on it in unusual places, as well as on the BCG and inside the upper as well.

hueyville
August 22, 2017, 08:33
I would try simplest solution first. Swap in any charging handle you have and see if it does the same thing just so know if it's the CH itself or another issue causing your problem. I have only bought one new fancy charging handle in my life. Gotten a lots in trades and junk box buys but recently found a deal on U.S. made milspec charging handles for $9.99 each with free shipping on orders over $100. Have a big box of assorted extended latches find in sale here and there and if a rifle needs an ambidextrous or extended just dig out best latch in box for job and keep building. Would love to find a big box of old milspec steel AR charging handles at fair price.

A fubared charging handle is a mess, have about half dozen stashed back and when build dedicated fighting rifles that will be put at top of stack for defensive/offensive rifles use one of my steel stash. Was stunned when my last 18" 6.8 build came out at 6.5 pounds with scope, 20 round Lancer mag and A2 stock. Was not trying to build a light rifle, just happened. Working on an 18" 6.8 now that just the upper will likely in excess of 7.0 lbs and ready to find time and finish to see if it shoots enough better than the lightweight to warrant the extra weight.

fuel fire desire
August 22, 2017, 15:15
Okay...... so after doing some research, talking with SI, and talking with a metallurgist on another board, this is my conclusion as to why this is happening...using a lot of what the metallurgist's told me.


Being the latch is opening fully as seen in the second pic in first post talking about this problem, with the gas system off and no bolt movement, I really think the two key properties at play here are Young's Elastic Modulus (http://www.engineeringtoolbox.com/young-modulus-d_773.html) and Density (http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html). Elastic modulus in this instance is the ability of the metal to store energy for a given displacement and the critical area being displaced is the small section of the latch which surrounds its vertical hinge pin. The high polar moment of inertia (https://en.wikipedia.org/wiki/Polar_moment_of_inertia) of the latch geometry creates larger displacements of the outboard (release trigger) section of the latch as metal density increases. These two differences should offset each other, except for the fact that the 'stop' for the latch in either case is the aluminum floor of the latch slot in the upper receiver.

The high polar moment of inertia of this particular latch geometry is likely the bad actor here. If the outboard release trigger section of the latch were reduced to a flat plate, as in a GI issue latch design, its polar moment of inertia would be dramatically reduced and it would not be able to respond to recoil impulse with anywhere near as much vigor.

I doubt I'd take the time to attempt to return the item to the original seller, as it was purchased back in April sometime. I'd have to review build notes to reference even where I bought it from. I can always use it on a future more traditional build. I plan on replacing it with a latchless style charging handle (specifically the SI Phantom or Blakhawk) to get myself completely out from under any other latch "springboard" issues with other similar extended latch designs.


When placing my thumb behind the handle while firing, little to no force was transferred into my thumb. Only a small tap. This was experienced with my thumb either 1" or 1mm aft of the closed position. I believe the only impulse moving the handle aft is the collision of the extended latch release against the handle itself when it reaches its most extreme swing of travel. Not mechanical interference with the gas key or over gassing (as this is a low mass setup on a 16" mid gas barrel with the gas turned way down).





TLDR: I think the initial recoil impulse is causing the extended portion of the latch to springboard off of the catch portion of the latch. An issue I have NEVER seen, or even heard of, on a 5.56 AR. So either SI has an engineering issue with the shape of their latch, causing it to act as a spring, or its an issue unique to this rifle.

Im thinking a latchless handle is the next thing to try. (I don't have a mil spec handle laying around to try in the mean time)

hueyville
August 23, 2017, 08:17
That was a mouthful. Glad I am happy with inexpensive milspec charging handles and don't have to understand all that. ;-)

fuel fire desire
August 23, 2017, 08:24
That was a mouthful. Glad I am happy with inexpensive milspec charging handles and don't have to understand all that. ;-)

Yay race guns.....

jhend170
August 23, 2017, 08:37
TLDR: I think the initial recoil impulse is causing the extended portion of the latch to springboard off of the catch portion of the latch. An issue I have NEVER seen, or even heard of, on a 5.56 AR. So either SI has an engineering issue with the shape of their latch, causing it to act as a spring, or its an issue unique to this rifle.

Im thinking a latchless handle is the next thing to try. (I don't have a mil spec handle laying around to try in the mean time)

If your theory is correct it's likely a non-milspec part not playing nice with another non-milspec part at the heart of the issue. It may come down to trying multiple latches to see what goes best with the SanTan upper. You may even want to contact them to see what they recommend or what they put on their Hailstorm model AR as it appears to be an ambi billet piece of some sort.