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HankC
October 20, 2017, 19:36
I have a 223 AR upper and it is way over-gas. Stovepipe 1/10 if I fire factory brass case ammo. Wolf steel case is better ,while it is weak, but still stovepipes. On my reload with 55gr FMJBT, 4064, I have to load down to 20.5 gr to be 100%. IMR 4064 load data shows starting load is 23 gr. 21.5 gr would stovepipe 1/20. I tried 20 gr 4064, all lock back but powder do not burn clean. I could just load light but at such light load, the rifle does not group well. When it was new, ran well with factory ammo, standard buffer and group tight. I guess it leaked when new but after 100 rounds or so it seals up and over gas. :cry:I am now running 4.9 oz buffer, but does not help much. I know I probably should try adjustable gas block, but I wonder if I can just move the gas block forward to blind the gas hole a bit. Anyone tried that?

Falfan2017
October 20, 2017, 21:58
Ya that could work if you can get it right and get it to stay in place. I tried to drill my own holes to pin a front gas block and it didn't line up quite right so I had to significantly enlarge the gas hoe to get it to run. :facepalm:

Stoney
October 21, 2017, 00:17
if you have a set screw gas block it would be easy to move it a RCH

Tuscan Raider
October 21, 2017, 02:27
Who made the upper?

aquaman
October 21, 2017, 08:42
Just like a steer, all you can do is try...

But do you really think you'll get your gas block perfectly misaligned over "your gas hole" to solve your over gas problem?

Friends don't let friends play with their gas hole.

Just get an adjustable gas block. They're less than $100

HankC
October 21, 2017, 09:32
Who made the upper?
It is Radical, 16" Carbine gas system. I know some dislike Radical, but it was great when brand new!;) My 7.62x39 Radical is great!

I googled and found one guy had the same issue, he contacted Radical and Radical says the gas port is .089", it is big! I can experiment how much to move the block but my main concern is how long it will last. There will be gas erosion to wear out the edge that blinds the gas hole. If erosion is slow, no big deal since I intend to shoot reload anyway. There are cheap adjustable gas blocks around $30, thought about just buy a cheap block and save the headache, but it will be fun to play with it a bit! Also thought about drilling a small bleed hole to vent the gas a bit, if does not work, I can always tap and put and set screw in to make a DIY adjustable block! Another thought is crimp the gas tube, but not brave enough to try it! The tube is thin, it may rupture under pressure if restriction.

richbug
October 21, 2017, 09:58
You can make your own "adjustable block" easy enough. Drill a hole from the side into your gas block where the port is between the tube and barrel(just half way through). Tap it. Screw a set screw into it. Once you have your gas adjusted properly, stake the screw so I doesn't move.

yovinny
October 21, 2017, 10:30
Please enlighten me,,,
Why are your thinking your previously perfectly working AR is now having stove pipe jams as a result of being over gassed ?
How could the gassing have changed ?

I'm sure no AR or much of anything expert, but I would have started by looking at the extractor, ejector, their springs and done a really good chamber cleaning,,,like with a real chamber brush on a drill.

But thats where I'd start on just about any semi-auto...
Especially one thats seen a bunch of wolf steel case....

meltblown
October 21, 2017, 10:44
Please enlighten me,,,
Why are your thinking your previously perfectly working AR is now having stove pipe jams as a result of being over gassed ?
How could the gassing have changed ?

I'm sure no AR or much of anything expert, but I would have started by looking at the extractor, ejector, their springs and done a really good chamber cleaning,,,like with a real chamber brush on a drill.

But thats where I'd start on just about any semi-auto...
Especially one thats seen a bunch of wolf steel case....

Same here. I don't follow a stove pipe from being over gassed. Though I've only built a couple of ARs.

HankC
October 21, 2017, 11:16
Changed ejector and spring, no difference. Checked extractor and removed extractor O ring, no difference. Swapped upper, lower and BCG, problem follows the upper. Since I hand load, I can experiment with different loads, lighter load less stove pipe.

yovinny
October 22, 2017, 16:25
Changed ejector and spring, no difference. Checked extractor and removed extractor O ring, no difference. Swapped upper, lower and BCG, problem follows the upper. Since I hand load, I can experiment with different loads, lighter load less stove pipe.

Ok,,I follow all that..

When you swapped out the lower, did the other lower contain the standard 3oz buffer and spring or did you also swap in that 4.9oz buffer ?

Sorry, I'm still trying to understand why a stovepipe means it's 'overgassed'.
When it doesn't stovepipe, does it chuck the empties to the next county ?

hueyville
October 22, 2017, 17:30
Remove front sight tower or gas block and measure distance to gas port where meets vent hole in barrel and distance to where lines up with hole in gas tube. Find a happy spot between the two and drill hole. A decent holding fixture and drill press help. Make sure and center punch your hole after mark where want it so drill bit doesn't walk. If you have a mill even better.

http://i66.tinypic.com/2lw4why.jpg

Can see from another angle.

http://i68.tinypic.com/t6rmg1.jpg

After drilled clean up well and use a blind hole tap or grind down point on standard tap or by time get nicely cut threads the point of tap will impact opposite side of gas vent and either strip your threads or start cutting into opposite side giving gas a divot to cause you to have to block more of the hole with your grub screw.

http://i66.tinypic.com/vfgkd3.jpg

Now you have a nicely tapped hole for grub screw, I use a hardened screw to prevent erosion.

http://i67.tinypic.com/30mlr3s.jpg

Thread in your screw, adjust till rifle runs exactly as you want, remove counting turns meticulously. Clean and degrease, apply Loctite and replace screw counting turns exactly the same number as took to remove. Test fire before thread locker dries in case needs tweaked but not too much as want your Loctite to stay and dry till screw has no danger of backing out. I have a more complicated system where drill partially into opposite side and use bigger screw that totally blocks gas vent then drill hole small hole through screw as slowly increase size till rifle runs correct. This allows me to drill a second screw for suppressor use. Just swap sews when install suppressor and rifle will be gassed correctly for can. Have a host of other tricks as well.

This is why we need a build tips problem solving stickies. At least third time have posted this.

4x401
October 22, 2017, 17:50
Stovepipe=Low gas pressure, too heavy recoil spring/buffer.

NOT, "Over-gassed".

HankC
October 22, 2017, 17:53
Ok,,I follow all that..

When you swapped out the lower, did the other lower contain the standard 3oz buffer and spring or did you also swap in that 4.9oz buffer ?

Sorry, I'm still trying to understand why a stovepipe means it's 'overgassed'.
When it doesn't stovepipe, does it chuck the empties to the next county ?

The other lower is my lower for 7.62x39 which has 4 Oz (maybe 4.6 Oz can't remember) buffer, heavy hammer spring and heavy recoil spring. Would not lock back with the heavy spring but still stovepipe. Not as bad. I don't really know how far it kicks brass since I reload and use brass catcher, standing brass catcher, not the kind attached to the ejection port. When shooting steel case, it kicks to the front and I don't really know where they land! Before it started doing stovepipe, it ejects brass to nice 3-4 o'clock, just like my good ARs. When it started doing stovepipes, it kicked brass to 1 O'clock and some even hit the free float handguard and leave dings on the rear edge of the HG. Front edge of ejection port has obvious ding marks. From time to time last spent casing would find in the chamber and facing backwards. With light load, it now kicks to 2-3 O'clock. This is my only AR doing this. My the other two 223 AR uppers run great with 3.0 Oz buffers and standard springs on the same lower before I switched the lower to heavier buffer. I haven't shot them for a while.

By the way, when I hand cycle, brass all eject fine at 3'Oclock and land 5 ft away. AR ejector is on the bolt, not like AK or FAL that ejectors are on the actions. On ARs, how far the ejection is independent from how fast the bolt travels (how hard hitting ejector). But bolt travel too fast may not allow enough time for the brass to be ejected out of the port. Not expert, just my opinion and the reason why I think it is over gassed.

Also, some say the stovepipe may due to bolt travel back too far and behind the ejection port opening. Not this upper. The bolt face is about 1/8-3/16" in front of the rear edge of ejection port. I tried bring the buffer tube in one more thread, no difference. Actually, when I look at my 2 308 ARs, the bolt faces are far behind the ejection ports.

HankC
October 22, 2017, 17:56
Stovepipe=Low gas pressure, too heavy recoil spring/buffer.

NOT, "Over-gassed".
Then why stovepipe 1/3 when I loaded to 26 gr 4064, less if lighter load and now at 20.5 gr it runs 100%?

yovinny
October 22, 2017, 21:16
I honestly dont know,,,but I'm just not seeing 'overgassed'
And while the AR has a plunger ejector as opposed to a receiver mounted one, bolt cycle speed will effect ejection.

I'm no expert, but Hell, I built a ton of AR's before I ever even heard the term overgassed used in reference to an AR...But those were all 'standard' type rifles, before the AR morphed into the thousands of options available today.

Personally, I'd run a chamber brush on a drill and clean the chamber spotless, put a standard buffer back in it and load up some factory LC ball ammo and try it.

Maybe I'm crazy,,,but it sounds more to me like youve got a lacquered up chamber from that wonderful wolf steel case ammo, than more of anything else.
IE: Regular loads in brass cases are expanding and sticking in the chamber for too long, while those less expanding and gripping steel cases seem to work and eject better....yours wouldent be the first or even the fiftieth I've seen that with.

Just my .02
Cheers, YV

Falfan2017
October 22, 2017, 21:44
An ar can be over gassed but not sure it would cause stove pipes. I've heard you may have failure to strip a round from the magazine and cause unnecessary wear and tear on the gun.

hueyville
October 23, 2017, 08:10
I honestly dont know,,,but I'm just not seeing 'overgassed'
And while the AR has a plunger ejector as opposed to a receiver mounted one, bolt cycle speed will effect ejection.

I'm no expert, but Hell, I built a ton of AR's before I ever even heard the term overgassed used in reference to an AR...But those were all 'standard' type rifles, before the AR morphed into the thousands of options available today.

Personally, I'd run a chamber brush on a drill and clean the chamber spotless, put a standard buffer back in it and load up some factory LC ball ammo and try it.

Maybe I'm crazy,,,but it sounds more to me like youve got a lacquered up chamber from that wonderful wolf steel case ammo, than more of anything else.
IE: Regular loads in brass cases are expanding and sticking in the chamber for too long, while those less expanding and gripping steel cases seem to work and eject better....yours wouldent be the first or even the fiftieth I've seen that with.

Just my .02
Cheers, YV


Bingo. Also mixing and matching lowers to uppers and expecting one buffer to be happy with all uppers is a mess. Lowers are freaking $30, triggers $19, stock $39 (with buffer tube, spring and buffer), plus $20 in other parts. I can often build a complete lower for $75 and Palmetto sells for $129 on clearance already built. I think too much swapping uppers and lowers is a mess waiting to happen. Anyone running Wolf, Tulammo or any lacquered steel case 5.56 or 7.62 NATO ammo will only have woe and misery. Buy an SKS if shooting steel case ammo.

Every build I do runs 100%, I adjust gas and swap buffers just to tune it to run soft as possible and still be 100% reliable. Build rifles out of free used parts abandoned by clients at LGS upgrading their OEM parts and screw them up using proper build techniques like torque values, squaring parts and using good ammo and have rifles with under $100 in parts investment that run 100% with non adjustible gas and standard weight buffers. Worked on an upper recently that was so out of square that has to chase threads after squared it. Guy who screwed it together had never heard of squaring the upper and when put the torque wrench on barrel nut to reassemble actually asked what kind of wrench I was using. If build your AR with nothing but a universal tool and magazine well holding fixture it's not going to be right even if works.

HankC
October 23, 2017, 16:16
but it sounds more to me like youve got a lacquered up chamber from that wonderful wolf steel case ammo, than more of anything else.
IE: Regular loads in brass cases are expanding and sticking in the chamber for too long, while those less expanding and gripping steel cases seem to work and eject better....yours wouldent be the first or even the fiftieth I've seen that with.

What you say make sense but I don't have any lacquered steel case 223s! I only have polymer coated steel case 223s and only shoot steel case occasionally. The chamber looks clean and I cleaned a few times after steel cases, I will give it a good clean up and try anyway before I monkey with it. Easier anyway.

hueyville
October 23, 2017, 18:30
Just an FYI for suppressor users with light machining equipment on homebrew gas blocks. Have the pictures on my computer but saving to put on my AR 15 site and if do a Utube channel will use there as well. A verbal description will do the job for those that can do the job.

Several ways to approach, screw (threads make for easy way to seal gas leaks), plug that uses C Clip and inserts into opposite side of front sight tower or bargain low profile gas block to support it and keep lined up and supported on both sides or method of choice based on tools at hand and imagination. I use a machine screw/small fine thread bolt. Locate best area of front sight tower or low profile gas block to drill a hole that is perpendicular to gas port travelling from barrel port and gas tube port.

Screw method:
Drill hole totally through gas block with pilot bit making sure it dead centered the gas pathway. The drill/machine out larger than diameter of gas pathway (generally about 0.160" diameter) enough that will be able to drill screw to become a constricting point allowing amount of gas flow you prefer. I use a #18 machine screw at 0.2947" diameter with 20 threads per inch pitch which requires a final drill size of 0.2280" before tapping.

Use an Allen hex drive button head socket cap screw and thread through front sight tower till head bottoms out creating a total stoppage of the gas pathway. Head may be slightly oversize and need to be turned down just a tad and if extends out opposite side in manner might create snag or just looks bad and can't get length from your industrial supply might have to machine down length a tad and chase threads. Now you have a single shot AR if reinstall as is.

Now choose a way to scribe a vertical or horizontal line, doesn't matter which, it's personal preferance. Line needs to be straight and true across end of screw and extend about 1/8" beyond on either side. I use a spring loaded center punch that fits snugly in sight tower gas pathway to mark dead center of pathway on screw. Now decide if want to start with suppressor on or off as we are going to drill two intersecting holes of different sizes perpendicular to each other. I generally start with can on and use an "S" stamp to remind me its suppressor line scribed when fully seated.

Remove screw and I start with a # 45 (0.820") wire size drill bit and drill hole, insert and test. Usually needs to be opened up more but can't make it smaller so take small steps. If doesn't cycle go to a number 92 then 93 and on up till rifle cycles with 50 grain, 55 grain, 62 grain, 69 grain and 77 grain factory loads. Usually end up in the # 44 (0.0860") or #40 (0.0980") range. 0.9335" seems to be a popular gas port size to run suppresed.

Once you have my port size correct for running suppressed, remove can and turn screw counter clockwise 90 degrees (scribe lines in block for the setting as well) and mark screw with centerpunch again. Start with a #54 (0.0550) and start working my way up till runs 100% reliable with 50 grain, 55 grain, 62 grain, 69 grain and 77 grain factory loads. Usually hit it before or buy # 44 wire size drill bit (0.0820). Believe Daniel Defense uses 0.0760" gas port.

Now for the worst part, sometimes a port needs to be opened up some so an adjustible block can have the available gas to operate or so I have been told and have read. The odd thing is I have never had to open a port except on a wildcat none standard cartridge usually on barrel that came undrilled and was too conservative when drilled port first tI'm as know can alays open more but shrinking a port is quite difficult. Many barrels have different port sizes based on length of barrel, length of gas system and diameter of barrel. A heavy barrel often has a slightly larger port size than mid weight or skinny barrel as port hole is longer thus gas is restricted for an increased length of travel. Port size is measure by many not in diameter but area. As in square millimeters/micrometers or square fractional inches. Unless a person is very confident in their build knowledge and skills or has really good information I caution against opening up ports but seeking a solution with different gas block.

Throwing this in for general information on port pressure since some folks like charts and graphs as port pressure is a subject builders and reloaders need to educate themselves about:

http://www.ar15barrels.com/tech/223plot.gif

To get this on topic I am still in agreement with others here. OP needs to agressively clean his rifle of all the goop from lacquered steel cases, polish chamber (can link threads where owners of reputible custom AR shops have said exact same thing about lacquered steel turning into glue in hot chambers causing rifles to seem to be malfunctioning when issue is cheap ammo and improper cleaning), and try some good brass case factory ammo. If doesn't fix issue then buy an adjustible gas block. Trying to slip one forward for partial blocking of port can work but is poor solution. Even though I sometimes build rifles for under $100 with lots of junk box parts, from sale parts in $250 range or nice rifles with $800 plus in parts not counting optics a person can be too cheap or ignore the real issue and create a bigger mess. Shooting steel ammo in AR's or nice 7.62 NATO battle rifles is ruining rifle and going to cost more in end than what's saved on ammo. Clean, clean again, then clean it and shoot some good brass case factory ammo and take steel cases and loading errors out or equation aND report back.

yovinny
October 24, 2017, 07:17
What you say make sense but I don't have any lacquered steel case 223s! I only have polymer coated steel case 223s and only shoot steel case occasionally. The chamber looks clean and I cleaned a few times after steel cases, I will give it a good clean up and try anyway before I monkey with it. Easier anyway.

Polymer, lacquer, whatever they happen to be using, it can cause issues.
Why those issues seem to differ between different rifles and why it leads to issues in rifle A, while seeming to never cause an issue in rifle B, is the real question...:confused:

And you usually cant see it in the chamber in my experience, or at least to my eyes. You can sometimes see evidence on fired cases, but again, that dosent seem to be without exception.

Where you'll see the evidence is on the cleaning patches after taking a rotary brush to that chamber and especially the neck area of the chamber, where it seems to migrate and build up and cause this issue..

Same issue we've see in the FAL years past,,,and why it's become well known to stick only with brass cased ammo and away from steel case wolf,,,but I've 'fixed' the same issue in probably 3x the amount of AR's now...And I only do work for friends or club members.:wink:

Btw,,,wet the chamber good with any cleaning solvent, run a chamber brush on a battery drill in there maybe 10 seconds, swab it out...repeat 3 or more times untill the patches come out clean...

HankC
October 24, 2017, 17:10
hueyville,

How do yo keep your adjustable gas block from stuck in one position? I read the screw will be frozen after maybe 200 or so rounds unless removed to clean the threads from time to time.
Also, in order to block the gas flow the screw needs to be at least the gas passage hole size, but I look at a low profile gas block, the gas hole is about #10 size and the distance between gas tube hole and barrel hole is also about that much which means if drilling is off a bit the screw will interfere with the gas tube or barrel.

EDIT 10/29/2017: Cleaned the chamber real good with bronze brush/solvent and also JB bore paste, went to range this morning. Still stovepiped with my reloads at 22gr of 4064 like before. Also tried reloads left over loaded with 22.5 gr 4895 that stovepiped before and I set them aside for bolt gun, stovepiped!

hueyville
October 24, 2017, 18:35
Below is a partial compilation of material have on port sizes. Actually have huge amount of data have researched, compared and put into charts that make sense to me and it's a constant work in progesterone as add information as find it. Currently have charts for 5.56, 6.8 spc II, 300 BO, 7.62 NATO (AR 10) and adding 22 Nosler along with other cartridges as find then confirm. Some is specific, some is a range. As in all things AR YMMV as every situation is different and as mentioned before, barrel diameter plays a role in port size as well as barrel length, gas system length and cartridge/caliber along with running suppressed or unsuppressed.

When read about some people opening up their port for increasing reliability makes me want to cry as absorb their preceived knowledge and experience building AR's. Others it's obvious they know what they are doing and fully comrehend the implications as well as have a logical reason to do so. If can't explain reason for opening port and theory behind what is happening across the entire system when do so your rifle may need to be at a gun smith sooner rather than later.

AR-15 Gas Port Sizes

24" rifle 5.56 0.0890"

20" rifle 5.56 0.0935"
20" rifle 5.56 0.0960"
20" rifle 5.56* 0.0980"

16" mid 5.56 0.0780"
16" mid 5.56* 0.0810"

16" carbine 5.56 *0.0625"
16" carbine 5.56 *0.0650"
16" carbine 5.56 *0.0700"
14.5" carbine 5.56 *0.0670"
14.5" carbine 5.56 0.0860"
11.5" carbine 5.56 *0.0810"
11.5" carbine 5.56 0.0890"

Length Barrel Diameter. Gas System O.A.L. Min Port Max Port Average Port Pressure
7.5" 3.850" 0.068" 0.077 41,223 psi
10.5" 3.850" 0.088" 0.093" 36,610 psi
11.5" 0.625 3.850" 0.079" 0.088"
11.5" 0.750" 3.850" 0.083" 0.091" 27,763 psi
14.5" 0.625" 8.375" 0.060" 0.075" 22,169 psi
14.5" 0.750" 8.375" 0.066" 0.083" 25,366 psi
16" 0.625" 8.375" 0.057" 0.074" 17,832 psi
16" 0.750" 8.375" 0.069" 0.085"
20" 0.625" 6.875" 0.085" 0.091"
20" 0.750" 6.875" 0.091" 0.095" 16,062 psi
24" 0.825" N/A 0.085" 0.089"

Gas System Lengths From Rear of Extension
Pistol Length 4.846" Approximmate 4"
Carbine Length 7.866" Approximmate 7"
Mid Length 9.866" Approximmate 9"
Rifle Length. 13.241" Approximmate 12"

Gas Port Pressure (Note for .223 SAAMI not 5.56 milspec)

http://ar15barrels.com/tech/223plot.gif

Average Gas Port Pressure:

http://www.guntweaks.com/uploads/1/9/6/5/19655623/ar-gas-gystem-port-pressure_1_orig.png

One of these end up on more of my carbine length budget builds than not. Some say does nothing but gas has to expand and travel same distance as mid length before starting the unlocking process of bolt. I also have these with two turns that extend the tube to full rifle length and mid length tubes with one turn that simulates rifle length gas in a mid length gas rifle. Need a way to measure recoil impulse on two rifles set up 100% exact except for curly tube on one and straight tube on the other. Have two rifles buit for that purpose. All is same except the gas tubes. Have no idea how I co u ld measure bolt unlock time and bolt thrust speed and force. Have used powders before that realized quickly had much higher port pressure in rifle firing.

CFE 223 is discussed by many to have extremely high port pressure to the point myself and others do not use it in 5.56 anymore. It's pressure curve is peaking at the mid to rifle port length in an AR barrel. Only AR load I use it for was my first batch of M855A1 projectiles in 22 Nosler as was most accurate powder when pushed past 3,500 fps with the miltary's new 5.56 projectile. Since my initial load development have read where others have found a powder that gets both velocity and accuracy out of them which is rare. Even dot mil uses a special batch of custom built M4's when they demonstrate the new round to the brass, congressional committees, etc who paid for them. Odd thing is they generally shoot full inch or even more smaller groups with a 1:8 barrel compared to both 1:7 and 1:9. Odd but well known among operators and prolific researchers.

The curly tube helps calm down the super high pressure curve passing gas port by giving a longer path for the gas to travel and more area for it to expand into. Luckily when discovered CFE 223 was only powder had in my inventory that would push the new projectiles over 3,500 fps and keep them in the 1.5 MOA range in the Nosler had one rifle length curly tube left have been saving for three years. Threw it own and combined with adjustible gas block and balancing gas flow, buffer weight and extending distance gas had to travel a tad my brass showed less pressure signs velocity stayed up with slightly less standard deviation and accuracy may have improved a tenth of an inch or so as slowed the gas system and bolt unlocking time down a tad. Have a long chart with times it takes bolt to unlock from primer ignition but this post is splitting enough hairs already.

https://cdn.shopify.com/s/files/1/0222/2126/products/cobratac_carbine_length_pig_tail_gas_tube_large.jp g?v=1471626779

Now to throw some more information at the OP who mentions how his reloads react oddly or differently than might expect in his overgassed rifle. I discuss then phenomenon more than occassionally in threads both in AR section and Ammunition section but going to quote from an article that have trimmed and then link to it in entirety.

different rate propellants will “peak” at different areas as*the expanding gases and the bullet travel through the bore. Slower-burning propellants peak further, and that means more pressure is available at the gas port location in an*AR-15, for instance, as the bullet passes it. If the system is oversupplied, then the system is overworked. Compared to ideal function when gas supply is delivered as engineered, mistimed peak pressures can result in the bolt unlocking too quickly and excessive bolt carrier velocity rearward. The system just gets hit too hard. The extractor tries to yank the case out of the chamber too soon, before the case is released from its grip on the chamber walls (from being expanded through firing). Spent-case condition shows a measurably more abused hull. Always keep in mind that this is all happening in about 2 milliseconds. The average time a bullet spends in the barrel, for most modern centerfire rounds, is 0.002-second. Timing is everything.

Moving the port forward effectively delays the wave of gas moving through the bore, kind of repositioning its peak with respect to its outlet; there is more space available for expanding gases. It also allows a little slower-burning propellant, which can take more advantage of the longer barrel.

All this changes with different chamberings and rifle configurations. Carbine-length barrels are particularly sensitive to port pressure because the port is located farther back.There are a few surefire things that will alert you when your rifle is exhibiting “over-function” symptoms, such as spent-case condition showing excessively blown (extended) case shoulders, extractor marks on the case rim, and a generally explosive sensation in functioning.

In a more extreme circumstance, an over-accelerated carrier can “bounce” back from its rearmost travel so quickly that a round can’t present itself in time to be picked up by the bolt, or the bolt stop can’t engage quickly enough to hold the bolt carrier.

Sometimes what appears to be a “light” load is actually not. I’ve seen excess pressure leave a spent case in the chamber because the extractor lost its grip, and I’ve seen chunks pulled right off case rims. That’s severe. That’s also another cause for the “short-stroke” appearance of over-function: the extractor issue has slowed the carrier. If you are having any problems with “over-function,” solutions include retrofitting an adjustable manifold, increasing carrier mass, and installing a stouter buffer spring.


http://blog.cheaperthandirt.com/reloading-2/

Am working from my tablet and bookmarks plus some files going to be using on my new website. Do not have all of my information at home so the 5.56 port information is incomplete but hope this post helps explain how many different things are going on. When you say your lighter loads work better, it may be that you have moved the pressure curve further forward and raised port pressure making gas system see a heavier load. Sounds weird but it's been discovered by more than me. I learned the hard way with CFE 223 and some out of spec bullets where had mixed weight pull downs in same bag. CFE 223 is a monster on chamber and port pressure if hit the wrong node when shooting a ladder.

So clean that rifle good. Get some decent brass factory ammo and try again. If problem persists my next move would be adjustible gas then play with gas settings and buffer weights till it was happy. If adjustible gas set for correct buffer doesn't fix the issue I do take in uppers from Files members and run them through my wringer for free. I even pay return shipping but can only take the upper, can't receive the entire rifle or lower. More than willing to help as fixing problem uppers is one of the things that has made me a better Lego builder.

Edit:
Spent twenty minutes laying out my charts so all data would line up under its appropriate headers. Looked perfect in preview mode and dang interface mashed it all together when posted. Now will have to put it all in a chart and convert to image so makes better sense. Had barrel length, barrel diameter, two different port size charts all nearly laid out with gas length and port pressure to all get squashed. Dang it. Most of you should figure out the data if need before get converted to charts.

hueyville
October 24, 2017, 18:52
hueyville,

How do yo keep your adjustable gas block from stuck in one position? I read the screw will be frozen after maybe 200 or so rounds unless removed to clean the threads from time to time.
Also, in order to block the gas flow the screw needs to be at least the gas passage hole size, but I look at a low profile gas block, the gas hole is about #10 size and the distance between gas tube hole and barrel hole is also about that much which means if drilling is off a bit the screw will interfere with the gas tube or barrel.

Yes, no room for error drilling your screw but they are cheap. If mess one up you out a nickle. After I finish machining they also get heat treated for hardness to reduce erosion. I have nice programmable heat treating oven but can do it the old fashioned way if want or plan on replacing when erodes. I don't do this often, it's more of a "can I make it work?", yeah it worked, shoot a few rounds suppressed and unsuppressed, get bored and put in vault with all the other stepchildren. My full on defensive, varmint and paper punching rifles usually have a nice commercial adjustible block. Love the Noveske Switchblock on a Noveske barrel but your $700 into a barrel and gas block.

Mostly with front sight towers do the grub screw, adjust gas for single purpose and lock it in place for life. The home brew adjustible gas blocks were a project to see if could make it work and if didn't have a decent lathe don't think could have kept it all sqaure even on my big commercial drill press. Probably cost me more in time than buying half a dozen adjustible blocks but sometimes I do thing just to see if it's possible. If have spare time, a half dozen screws odds are most can get it to work. I use anti-seize goop on my threads.

Have not really put one of described adjustible blocks in combat conditions. May hold up 10,000 rounds but the two in the vaults saw a couple hundred or so rounds each before put them back. Only have two settimgs, suppressed and unsuppressed. Your gas flow adjustment is done with the drill bits and stays static. Suppressed or turn 90 degrees for unsuppressed. Imagine one could turn some on its own under heavy sustained fire but put one on a binary lower one range session, screwed on quick change can and ran a half dozen mag dumps back to back with no issue then did the same with suppressor off in umsuppressed setting.

MistWolf
October 25, 2017, 21:10
Stovepipes in an AR aren't cause by short stroking.They are caused by either ejection or extraction problems. My thoughts are that it's more likely to be ejection than extraction.

HankC
November 05, 2017, 10:57
Update!

I fixed it by moving gas block forward 0.080"! Put the 3 Oz buffer back, fired 80+ rnds factory ammo and some of my reloads, that stove piped before, all good!

As I edited last weekend in post #22, a deep cleaning of the chamber did not make much difference. I decided to experiment moving the gas block to blind the gas port. I know I should just buy an adjustable gas block, but I had a hard time to remove the flash hider! I don't have a barrel vise. I want to experiment with moving the gas block anyway. Below is how I determined how much to move.

With gas block coming off the barrel gas block stop, I checked the gas port size with drill bits, it is indeed 0.089"( #43 drill bit) as reported by another guy on internet. Way too big! While the gas block has 10-32 set screws and block gas hole is opposite to the rear set screw, I guess they likely machine the 2 holes together and #10-32 drill bit size is #21 which is 0159".
If the gas block hole is perfectly aligned with the barrel gas port, moving 1/2 of the block gas hole diameter will blind 1/2 of the barrel gas port and give me 0.089/2 =0.0445" gas passage!

While Colt 16" barrel AR Carbine has 0.063" gas port, so is my spare Anderson barrel, 0.063" is the goal. I just need to be close, don't need to be perfect since I reload anyway.

Another factor is the barrel gas hole position vs gas block. I measured the distance from the gas port CL to barrel gas block stop, also the distance from block set screw hole CL to the rear edge and determine the gas port will be 0.02" forward to gas block hole if the gas block is installed against the stop which is how it was before. Using barrel gas block stop as the reference point, my math tells me --

Moving gas block .08 away from the stop, the port hole should be .0445 + (.0795-.08) + .02=.064 egg shape!

The barrel gas hole has carbon residuals around it, the distance between the rear edge of the carbon mark to the gas port rear edge is roughly 0.055". If I move 0.080" will blind the gas port by 0.025" (0.080-0.055). The 0.089" gas port dia - 0.025" = 0.064" Confirmed!

I use feel gauge to shim the block to position the block to 0.080" when reinstalled.

Works now! Not sure how many rounds it will last due to gas erosion but I'm happy for now.:)