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Old November 16, 2019, 19:50   #1
hueyville
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AR 10/LR 308 Adjustable Gas Blocks

Got a PM asking about AR 10 adjustable gas blocks. Below will be the response I sent to user who asked. I love Superlative Arms Bleed Off gas blocks on AR 15s so was first unit put on a jumbo AR and discovered it didn't function properly in bleed off mode so had to do a bit of research and learning. So now to my PM reply below and let the flames, disagreements, name calling and thread drift begin!!!

My quick answer and now we can hash it out like a bunch of middle school kids on the playground:

Often it's what I find on clearance sale from a reputable vendor but be sure its marketed for AR 10 by manufacturer not just retailer. What type of build is this, a mostly milspec get rounds down range reliably or a rifle that will punch tiny groups and make first round cold bore kills at extended distances? I consider the barrel the heart of a build. What price range barrels are you considering? If buying a $400 to $900 premium tube will want more adjustability to slow cyclic rate down as much as possible while keeping 100% reliability. If buying all bargain Palmetto or similar parts for a build to launch rounds you just need the ability to rough tune gas for reliability.

I use Superlative Arms bleed off gas blocks on most of my mid to upper tier AR 15 builds but read this discussion thread about what happens when used on an AR 10. It will educate you some on how AR 15 adjustible gas blocks are not as happy, happy, joy, joy on a jumbo AR build.

https://forum.308ar.com/topic/14657-...ble-gas-block/

Notice Primary Arms has an entire section of gas blocks they sell specifically for the AR 10 and the Superlative bleed offs are included. People and especially vendors do not seem up to speed on the different needs between to two rifles and seems to be an assumption if it fits it will work.

https://www.primaryarms.com/MCategor...308-Gas-Blocks

This thread discusses the issue deeper and as I have found an adjustable gas block, especially if use suppressors, is necessary on many AR 10s but few manufacturers are throwing research and design toward an AR 10 specific block.

https://www.ar15.com/forums/ar-15/Ad..._/121-691997/?

Syrac Ordinance advertises this block for both AR 15 and AR 10. Understand it uses a flat wire spring inside that seems to stand up to the AR 10/AR 308 better than others. I have three on AR 10 builds of mine and have given me no trouble and done the job asked thus far.

Syrac Ordnance Gen II Click-Adjustable Gas Block

https://www.midwayusa.com/product/1003403975?pid=332827

http://www.nokick.com/Syrac_Lockable...so-agb-cob.htm

JP makes several adjustable gas blocks marketed for use on both AR 15s and AR 10s. I have two different models of JP adjustable blocks on AR 10s, one of each linked and both do what I wanted them to do. One was $49 and the other $99 on sale but links show street price a bit higher. Actually bought two of each during sale but the other two are in parts locker unused as of yet. When see a sale on good parts buy extra....
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Old November 20, 2019, 20:47   #2
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Almost stunned this thread has gotten no discussion. Have always read manufacturers specs before installing an adjustable gas block before using on AR 10 to make sure it's rated for a jumbo AR. Even on AR 15s there are lots of specialty parts for AR 15 pistols like buffer assemblies that are for 5.56/300 BO only. Can't use with 6.8, 22 Nosler, 458 SOCOM, Valkyrie, 6.5, 270 AR, etc. I do have some Battle Arms Development short 4" pistol buffers rated for 5.56/300 BO only that have modified for use successfully with 6.8, 22 Nosler and 458 SOCOM (only in subsonic for 458). Dead Foot Arms 2.5" buffer is 5.56/300 BO rated only but have modified so holds up to 6.8 and 22 Nosler.

When began building AR 10's in 338 Federal, 6XC, 6.5 Creedmoor and 358 Winchester to experiment with best cartridges to do specific jobs ran into issues that when throwing AR 15 parts on oversize receivers. Have a 13.7" 358 Winchester with pinned Form 1 suppressor that built when looking to achieve a high horsepower subsonic rifle. Liked fact 358 Win uses a 308 bolt face and finding someone to spin me a barrel wasn't overly difficult. Wanted to go shorter and had read that a 12.5" tube with 1:12 twist would work but limited choice of powders to get complete burn before projectile left muzzle so ordered up a 13.7" 1:14 twist 358 Federal barrel and pinned a 5.5" Form 1 can built with over size diameter tube to get as much internal volume and still keep barrels OAL as short as possible.

Using Barnes 250 grain Tipped Triple-Shock X (TTSX) copper solids whether in subsonic or supersonic full power are impressive stoppers. Cast 250 to 285 grain gas check bullets are inexpensive and still develop an impressive thump in 358 Win. 250 grain Woodleigh Hydrostatically Stabilized will break down a grizzly bear. Nosler 250 grain Accubonds will deliver a thump to big game as do Woodleigh 310 Grain Weldcores along with a host of projectiles in the 250 to 300 grain range.

At one time had gone AR 15 crazy and built poodle shooters in 5.728, 20 Practical, 204 Ruger, 223/5.56, 22 Nosler, TAC Six, 25-45 Sharps, 6.5 Grendel, 6.8 spc II, 270 AR, 300 BO, 300 OSSM, 375 and 458 SOCOM and a mix of various wildcats. Except for leaving one pair of 5.728s with binary triggers for wife when her bones are aching more than normal I tore down every AR build I had that was not in 223/5.56, 22 Nosler, 6.8 spc II and 458 SOCOM. Those four cartridges will do everything possible I have found in an AR 15 chassis and allowed me to sell a bunch of low round count barrels to buy barrels in my four cartridge fleet plus freed up a pile of parts to build the extra rifles in my four standard poodle shooter cartridges.

Like the years of playing with AR 15 cartridges to find the ones that best suited me am now in same mess with AR 10s. My first pair were in 338 Federal. Second pair was a gift from God as was able to buy a pair of $900 retail 6XC barrels for $100 each and a White Oak Armament built side charging and top charging upper for $250. Ended up with a pair of 6XC gas fed rifles that will float 115 grain DTAC bullets out to 1,000 and 1,200 yards with absolute surprisingly stunning accuracy and only had $1,500 in the pair not counting optics.

Where I really learned about AR 10 gas blocks needing to be built a bit tougher than AR 15 was the first 358 Winchester mentioned above. After working up a myriad of loads for it and running a ton of cast through it along with super heavy subsonics and full power supersonic loads began having issues changing settings on the gas block. Was a pain to unpin the suppressor to get the block off and it was near welded in place. Discovered where gas port in barrel vented gas up into block the gas port in block was showing major erosion along with adjustment screw and detent spring had come into pieces. Had to find a replacement that would not erode as quickly and especially eat up any small internal parts before even had rifle broken in. Did a lot of research and rebuilt the 338 Win.

Soon as my next pair of ultra premium 6.5 Creedmoors come off the bench plan is to build either a 450 Marlin or 450 Raptor. Am also intrigued by the 375 Raptor as well so odds are at least one will get built for testing. Also becoming intrigued with the 500 Krater and it's 5,000 ft/lbs of muzzle energy. It uses a cut down 300 RUM case and holds about a half keg of powder. It is also extremely accurate and likes Barnes copper solids and a lot of the LeHeigh specialty projectiles. My guess is like AR 15s will end up building ten or twelve different cartridge AR 10s, test the lot then pair them down to four or five total cartridges that best suit my needs for the AR 10 fleet. Of course this means when building rifles like the 500 every part including gas blocks are going to have to be carefully selected or may be picking some of the small bits and pieces of an adjustable gas block out of my weak hand. Don't think many AR 15 parts makers are considering their gas block might end up attached to an AR 10 designed to kill dinasaurs.
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Old November 20, 2019, 20:55   #3
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I am curious about AR-10 barrels and adjustable gas blocks - but I'm also wayyy over budget on firearms expense for the year and my PSA-10 runs just fine for the moment.

I may investigate this later, as I think my PSA might benefit from a better barrel and possibly a slower/less violent recoil impulse. My is likely over-gassed from the factory to be reliable but it's not easy to hold shot after shot off the bench. I do really enjoy shooting it though.
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Old November 21, 2019, 00:19   #4
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I find a lot of rifles over gassed to ensure reliability rather than returns to factory. Daniel Defense swapped port size several years ago on AR 15s when started getting people using steel case Chinese ammo sending their $1,200 to $1,800 rifles back for function issues. We would show owner they worked fine with M193 which is dirt cheap but they didn't care wanted to shoot the super cheap Chinese ammo.

In same circumstances I might make same decision or just put an adjustable block on from factory with simple three position lever on my $1,000 plus gas guns with instructions to use setting that gives 100% reliability with least felt recoil. All $399 to $499 rifles would over gas them a tad. I like to tune my rifles for best function and accuracy so use a lot of adjustable gas blocks and keep a full variety of buffers in range kit.

Building all the odd balls, especially wildcats where port size has no standard and can't buy factory ammo then adjustable gas is mandatory. Also never can tell when I am going to swap a rifle over to a suppressor. Recently was at range with friend who had a Palmetto AR 10 in 308 and I happened to have one of my DPMS Oracles with a binary trigger. He wanted to try the binary trigger and was stunned to discover the recoil impulse of my rifle with two rounds going off almost simultaneously was less than his Palmetto firing singles.

I went to truck and swapped his buffer spring to a chrome silicone flat wire then upped his buffer weight two numbers and he was a grinning fool. Told him if wanted to spend 100 bucks to float his forearm and add adjustable gas could shrink his group size and reduce recoil a tad more. Next paycheck he is brining his upper to the shop, I offered to fix it now and let him pay parts bill when able but he wants to shop forearms rather than just choose from the dozen or so AR 10 units in my parts locker.
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Old November 21, 2019, 14:03   #5
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So by your last post, I could potentially shrink group size by:
  • Adjustable gas block
  • Additional weight in bolt carrer
  • New flat wire recoil spring

Might be worth a shot. Certainly easier than removing the whole barrel assembly.
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Old November 21, 2019, 14:52   #6
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Even more if add free float forearm at same time. What your doing is increasing time bolt stays locked if do it correctly allowing projectile to be farther down range before bolt unlocks and starts causing rifle to move. Same principle as too little travel in trigger and hitting trigger stop before sear drops hammer, moves firing pin, igniting round and sending projectile down bore. Learned this years ago with F Class rifles and trying to take all creep an travel out of triggers. Removing the creep is good but when trigger trips sear need a little movement for follow through or trigger hitting stop will move rifle before overcome lock time.

Adjust gas to slow cyclic rate and keep bolt locked longer will keep rifle settled till projectile totally clear rather than quick bolt movement inducing movement of rifle before projectile clears. I can set up an AR with over 1,000 rpm cyclic rate or slow it down to 550/600 rpm. On my varmint and paper punching rifles have adjusted cyclic rate and found for me if keep them at low side of 600 rpm vs 900+ rpm will get better groups. Also by adjusting your cyclic rate to slower speed can reduce recoil which in itself increases accuracy.
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Old November 21, 2019, 19:53   #7
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When I bought a Windham Weaponry 308 a number of years ago I contacted them about using a can on the rifle. They told me they recommended the POF Dictator adjustable gas block. Said most of the guys in the plant were running them on their personal Windham 308's. I put one on and it's been flawless in the years since I installed it. The only problem I did have was POF didn't include the screws to install the gas block. We called two or three times and each time the lady said they were shipping them out that day but they never arrived. I got tired of the run around and just ordered a small box of that size screw from some out fit I forget the name of now.
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Old November 22, 2019, 08:15   #8
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I noticed as of today the Syrac Ordnance thingie is being reported as discontinued in may sites duckduckgo found.
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Old November 22, 2019, 17:56   #9
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Quote:
Originally Posted by raubvogel View Post
I noticed as of today the Syrac Ordnance thingie is being reported as discontinued in may sites duckduckgo found.
As happens to many good products that cost a few dollars more. Price shopping in a glutted market where many consumers don't look much deeper than price and function kills many a fine product. Good thing I tend to stockpile performance parts when find on sale so have enough to tide me over while researching their replacement.

For the money Ergo adjustable gas blocks are the best buy but I only use them on mid level poodle shooter builds where adjustable gas may be needed on occasion for a suppressor. Can get them for $39.99 to 44.99 street price and have a big pile from a $29.99 sale last year. Have used them on 5.56, 6.8 and 22 Nosler but not on any that will be adjusted often. Mostly use as a way to tune gas as cheaply as possible on rifles want to do more than swap buffer weight.

Have big pile of Superlative Arms Bleed Off but those are for 5.56, 6.8 and 22 Nosler suppressor builds or premium varmint rifles want to fine tune my gas and keep as much gas out of receiver as possible. If get in a bind can usually count on JP to have a precision adjustable gas block for specific need but generally pay for their products. That said I probably have over fifty JP 3.5 Enhanced Reliability Spring Kits purchased when on sale marked down from normal $9.99 price to $6.99 as know 70% or more of all milspec triggers I install will get their spring kit in the fire control system.

Have not done a recent big dig research effort on AR 10 adjustable gas blocks but with several builds already mostly gathered plus several others planned to point have secured receiver sets just in case world goes loopy and prices for receivers triple or more they are in house along with my normal extra sets keep as feel unprepared if don't have spares. Had 1,800 rounds of M193 5.56 ammo that I really have no use for come in this week because it was dirt cheap with free shipping and if ammo prices go loopy will lament letting the deal I got go by without bringing a few more in. Have a nagging feeling that dirt cheap AR anything prices are soon to be a thing of the past.
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Old November 22, 2019, 18:04   #10
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SLR is great and adjust form the front. I use SLR on my 308 AR as well as my AR15s.
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Old December 03, 2019, 00:31   #11
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I just ordered a 22" X-Caliber 6.5 barrel to use for one of my 6.5 builds as felt it was a fair price, get good reviews and have lots of options. First opotion I really liked was ability to choose larger muzzle thread sizes to give more meat at muzzle to reduce chances of belling. I went with 3/424 thread size which is an extra 0.125" of meat at threads. For fifteen bucks was able to throw in bead blasting which saves me the effort, just degree and shoot it with a load of Cerakote in whatever color suits me on day it gets color.

Also for and extra $80 they will cryofreeze which in my precision bolt rifles over the years has always done well and my rifle smith still recommends all his clients send their barrels off for cryo treatment or order them with it if offered. Gave the option for gas length up to rifle +2" which of course I clicked on the extra two inches then on gas port it gave option of non adjustable gas block or adjustable. If choose the non adjustable they drill port best size for cartridge and length of gas system. If choose adjustable they drill port slightly oversize so user can crank up the gas if they want but they don't necessarily recommend this they just say with a good adjustable gas block have a wider range of gas settings if have a larger port.

Got to totally configure as much of barrel as I wanted from diameter to rifling which I chose a 1:9 5R since all my other 6.5 tubes have 1:8 twist. Figured doing so much different may as well mix the mongrel up as much as I could without going completely nuts and price tag totaled $435 which feel is quite fair. Barrels are hand lapped for whatever that is worth. It's the skill of person doing the lapping, not just the fact it's hand lapped. By late spring should have a good selection of 6.5C rifles with various barrel prices, lengths and rifling to see if can turn out one or two that will shoot. Am interested to see if the extra bit of twist allows stabilizing longer and heavier bullets for days a man may need to buck a hard to read wind.
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Old December 03, 2019, 09:32   #12
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1:9 is slower than 1:8. Isn't that contrary to the customary idea that a faster twist is better for long, heavy bullets? Just curious about your thinking.
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Old December 03, 2019, 10:46   #13
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I've had the Superlative Arms and the SLR gas blocks. I have about 8k-9k .223 out of the Superlative, and while it has finer adjustment points, it does seem to get carbon fouled heavily after that many rounds. The SLR seems solid, I have a GenII version, but I haven't had enough through it to tell. I would say though, if you plan on suppressing and fine tuning it, go with the Superlative.
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Old December 03, 2019, 11:55   #14
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Quote:
Originally Posted by M90A1 View Post
1:9 is slower than 1:8. Isn't that contrary to the customary idea that a faster twist is better for long, heavy bullets? Just curious about your thinking.
Yes, it is.

I have the SLR block on my 6.5 Creedmoor. Great accessory
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Old December 03, 2019, 13:46   #15
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Was thinking backwards. Read way too many ads in four days. It is actually a 1:7 twist 6.5C barrel from X-Caliber. Bought the BSF carbon wrap in 1:8 and ended up finding an 18" single point cur rifled barrel just a little bit after I made that post so way fat on 6.5C barrels now.
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