[BLACKTAIL 8541]

If it ran fine with the original gas block and is now short stroking with the new gas block , you have a gas problem, alignment issue. Do not cut coils off your recoil spring. When you get it functioning again you can damage the gun by excessive impact to the receiver / extension.

 

[Sailormilan2]

I agree with Blackrtail in that you have a gas block issue. When I bought my first 308 AR, a Palmetto PA10, the word was that 308 ARs were often over gassed. Which could lead to "jamming" issues that were sometimes mistaken for being under gassed, ie. short stroking. The bolt was actually going too fast. I also had issues with the bolt not closing fully on the round. That was solved by removing the "donut" under the extractor. Easy job.
My recommendation, is to replace the the gas block, which is probably just a simple, standard non adjustable one. Replace it with an adjustable one. It's actually not hard to do. The hardest part being reinstalling the roll pin that holds the gas tube into the gas block. With the adjustable gas block you can now regulate how much gas that goes into the system. ALL of my AR pattern rifles have adjustable gas block. I don't use the top of the line models either. I'm cheap. I use the cheaper versions.

 

[Plinky14]

I have heard of PSA 308 AR's or their parts not being made to match anybody's 308 AR standards, and people having problems especially when replacing parts or trying to build one custom using their stuff. I had looked into possibly doing a 308 AR build or buying one using their stuff, they're cheaper than many other brands - but I kept running into reports of people having problems and no real solutions. Cheap is often not your friend in boomstickery and it sounds like that can really be the case with 308 AR's and parts.

In general it seems you have to be more careful selecting parts / brands building 308 AR's. There is no de facto standard all parts are made to but instead, a few different types. You can build a certain type (DPMS pattern is a good choice) but sadly on top of type naming by manufacturers there is a lot of confusion and mis-naming of types seen out there. For example, you can find companies out there selling what they call an AR10 "DPMS" Lower. 2 separate animals so those 2 terms really don't belong together.

Even so, you still really have to be careful mixing brands of parts even if all are made to "DPMS / LR308" pattern. Standards is a pretty loose term with 308 AR's and frankly there is some pure junk out there even among those known for high quality AR15 parts. This is another instance of it being best to check with others who built successfully.

Gas systems apparently tend to be very common places you can run into trouble with 308 AR's, there is even variation in where barrel manufacturers locate the gas port and journal - and sometimes as a result the gas tube won't be "long enough" for proper amount (duration) of gas flow from the tube into the gas key to get the bolt/BCG fully out of battery before the supply of gas runs out. ie, the gas key clears the gas tube prematurely and you don't have enough gas to fully cycle.

The 308 AR forum mentioned above is a good place to educate yourself on these issues. There are several people over there who really know their shtuff especially the guy with a shortish alphanumeric handle 85-something-or-another with a gorilla face avatar. I agree they are highly opinionated over there and a little blunt sometimes but when you see the same questions and problems posted over and over again that could have been avoided had the user read/studied some of the guides and troubleshooting pinned posts, or heeded good advice they were given trying to get something working, that I get being a little pointy.

It's best to spend a little time searching, there are some great guides over there.

 

[Jackofalltrades03]

For example, you can find companies out there selling what they call an AR10 "DPMS" Lower. 2 separate animals so those 2 terms really don't belong together.

They did a revision at some point adding a second extractor calling it a Gen II. I think there is some type of interference that doesn't allow them to interchange, but I could be mistaken.

My first Gen LRT SASS has never missed a beat

 

[migunshooter]

It's a under gas issue. how far into the upper receiver does the gas tube extend?

 

[Cool Breeze]

Some time ago a friend had an Armalite that continually jammed no matter what we tried, turned out there was a recall and something wrong with the bolt, receiver or both requiring replacement and or modification at the factory. After that it ran fine....

 

[Jarhead504]

Brother dozerhand: Go to and register at 308AR Forum.com. Those guys over there are the equivalent of the M-14 experts here. They will help you.

I stayed away from the AR-10 Coven as long as I could, but now I have been inducted into it with the AR-10's arts and allurements. Hey, even Brother Art joined in.

Tell them Jarhead504 sent you.

Jarhead504

 

[nf1e]

Yep, they will analyze and suggest corrections in about 5 seconds. Nice to have folks that know their stuff and willing to help newbies.

 

[Tex1001]

I don’t buy the “AR-10s never run right” line.

I agree. The same statement (incorrectly) could be said of almost any firearm design.
I got hooked into a very cheap DPMS 308 Sportical and immediately decided to do a rebuild
because of so many features I didn't like.
It runs like a sewing machine now, after the debugging.
I received help on the project from several here (Thanks guys).

 

[Plinky14]

Yeah once upon a time, one of the last times I took my plinker M1A out to the range (circa 2014), I ran into a couple of young guys that had what they said was a DPMS 308 AR, I liked it. It even had some kind of carry handle and A2 style gas block and pinned FSB on it too... that might have been when the gears first started turning in my brain about a 308 AR... hehe.. but it was nice looking, usual M16/M4 type 2-piece handguard etc. I didn't know what I know now, you don't seem to see many 308 AR's in a true A2 type configuration these days. I don't remember if the carry handle was detachable or not.

They were having a hell of a time hitting anything with it. But it was a problem of.... basic marksmanship. So I tried to sort of help spot them and get some grouping on target, tell them about sight alignment, etc. But it just wasnt going to happen with these guys. They were decent enough and friendly but in the end I ended up wondering how they got that rifle. Or why. There's a detail or two about those guys I'll just... leave out. But they weren't really listening to me. So I just went back to shooting my rifle.

 

[82nd ABN]

I have two custom Armilite AR-10's i built and both run 100% fine all the time. I dont think your problem is the gas block at all. I think it is the weight of your buffer. You said you took coils out of the spring to reduce the force, I would rather have the spring force with a lighter buffer. You do know that buffers come in different weights right? Anytime I ever had a problem with short stroking it was always the combination of the spring and buffer weight. What weight is your buffer that is installed now? What spring are you using? I don't know where you are located but I wish you were around me in PA I would have it running like a champ. I had an AR-15 I built that wouldn't run right. I bought a nice silicone carbide spring and an enondyne hydraulic buffer. It was a 28 inch bbl with the gas port at 14.5 inches. I went and bought a standard rifle spring and buffer and it worked fine. I tried using a combination of spring and buffers and it would not work in any other combination other than standard. I dont know if you have a buffer you can remove weight from but I would get a standard spring and try lightening up the buffer. It is a carbine, does it have a carbine lenght gas system? typically the port is 10.5 inches from the face of the receiver. I am sure that thing has enough gas pressure. I think the buffer is too heavy.

These are two -10's I built using Armilite uppers and lowers as well as their upper and lower parts kits, I also used their buffers and springs and the A2 buttstock and A2 handguard. The rest of the parts are WOA JP Krieger ect. I do run an superlative arms adjustable gas block on the one with the 30 inch bbl.

 

[dozerhand]

Thanks for all the help. This has been an ongoing problem for about five years. A non functioning firearm is no more than an expensive club.
To be clear, it has the correct gas tube. I find it hard to believe that three different smiths failed to align the gas block correctly, the first was a name many of the long range shooters in here would recognize and as a matter of fact I got his name from this group. I wouldn't be surprised if many of you would also recognize the name of the second smith. The third was a local feller of good reputation around here. I was the last to try aligning the gas block. I was very careful to be sure that it was aligned correctly. I I stated in a previous post, I marked the barrel and the block to be sure that the ports lined up. As much carbon as it produces in the bolt carrier you would think if it was leaking around the gas block there would be some sign of it. Today I performed a thorough cleaning and then ran several magazines through it pulling the bolt by hand. Every round cleared the receiver even with a bullet intact, so I don't think it's the ejector. I have replaced the buffer spring and am going to borrow a friend's upper next week and return to the range for a test. If it won't run I'll suspect the lower. If it runs I'll try my upper. If it still won't run I'm going to start saving my money for a new upper. I probably could have bought a whole new rifle for what I've spent on gunsmiths over the last five years. Then I'll have a rifle and I can work with this upper myself when I feel like it. If I get it to run great, if not I'll still have a rifle.
later, dozer

 

[dozerhand]

I am sure that thing has enough gas pressure. I think the buffer is too heavy

View attachment 513301

DPMS style not Armalite, A2 stock and hand guard, 18" standard barrel with mid length gas system, flat top upper with MBUS steel rear and YHM folding front. I'm going to look into the buffer weight, the only thing is that it worked with the original buffer and spring until the gas block came loose. I only changed the buffer and spring after replacing the entire gas system and BCG. But a buffer is a low cost solution compared to replacing the gas system, again.
later, dozer
p.s. the second gunsmith after replacing the gas system and buffer with spring. Told me that the gas port in the barrel was too large and the barrel needed replacement. Does that even make sense?

 

[brianns]

I sympathize. After 7 yrs I finally figured out I had a bum bolt carrier for my 6.8spc AR. I tried or examined many many things before finally trying a different one in the rifle. I wish Your YHM gas block worked. I’ve considered using them at some point or the RockRiver one that’s similar.

 

[CHARLIED308]

I suggest installing all of the original parts that worked and locate a gas block like the original. Use a magazine that was known to be reliable when you first bought the weapon. Once you know the weapon will run reliably, change one component at a time, not two. When you replace more that one part that affects the gas system, you can run into trouble without knowing which new component caused the problem.

I have some experience with the Armalite AR-10 rifle (not carbine) and they can be ammunition sensitive. They can be set up to run reliably with 168g HPBT Match or 150g FMJ, but normally not both. When the factory set up runs well with 168g HPBT Match, changing the buffer spring may be necessary to run ammunition with lighter weight projectiles. Many have successfully used an AR15 buffer spring to shoot lighter projectiles.

 

[82nd ABN]

DPMS style not Armalite, A2 stock and hand guard, 18" standard barrel with mid length gas system, flat top upper with MBUS steel rear and YHM folding front. I'm going to look into the buffer weight, the only thing is that it worked with the original buffer and spring until the gas block came loose. I only changed the buffer and spring after replacing the entire gas system and BCG. But a buffer is a low cost solution compared to replacing the gas system, again.
later, dozer
p.s. the second gunsmith after replacing the gas system and buffer with spring. Told me that the gas port in the barrel was too large and the barrel needed replacement. Does that even make sense?

Yes and no. A gas port hole diameter is related to the bbl length the distance from the breech and muzzle all these predicate the hole size which sets up the dwell time. I am 100% positive the problem lies it the spring/buffer. Here is one for you, years ago when I built my first AR-15 I was concerned about the gas block alignment. WHat I did is going to sound weird, I took a rubber hose and put it over the gas tube in the upper receiver. I then blew through the hose as I adjusted the thing left and right. When I tightened it down the thing was perfectly centered on the bbl. Since then all the rifles I have built get line up by eye and I never looked back and they all worked. I have used a digital angle finder to align the one with the picatiny rail and the rail on the upper receiver and a reference. A clean rifle is a good place to start although these things are designed to run pretty dirty with no lube. I am certain the problem lies in your spring/buffer combination. A buffer weight for an -10 should weigh between 3.8-5.4 ounces i would imagine you have a roll pin holding the front cap on the buffer. See what it weighs and maybe take one of the weights out providing there is more than one weight in the buffer. Do a little research on different buffer weights and cycling. This may be a good place to start. The Heavyweight Guide to AR15 Buffer Weights
You just have to find the right combination of spring and buffer weight.

 

[peckens]

My buddies brand new Aero ar10 managed to put a bullet sideways into a target at 50yds the other day. Not sure how that happened lol

 

[brianns]

Odin Worx has adjustable weight buffer kits too.

 

[Para Pete]

I stayed away from the AR-10 world for decades until I decided my Scout Squad needed an AR cousin- so I picked up an Adams Arms P1 MOE 16" Small Frame .308 piston AR (DPMS Gen II platform). Good Golly, Miss Molly am I impressed with that rifle.

Now, my heart still belongs to my M1A, but if I was reaching for a rifle to take care of "immediate business"- I would grab the AA P1.... without hesitation.

Ergonomically, the AR is simply superior to the M1A for me- the pistol grip and VFG really make a difference with my physical disabilities. The P1 is almost a pound lighter than the Scout Squad, and it definitely kicks a tad bit more- but the P1 is easier to maneuver due to less weight and the shorter length. And when shooting side-by-side with my standard (DI) AR-15 (300 BLK), I can conclusively say the piston AR runs measurably cleaner than the DI version- there's just no denying that. Also, it is much easier for me to disassemble and clean the .308 AR than either the M1A or the DI AR.

Bottom line: both my M1A and SF-308 AR (and DI AR, for that matter) have been 100% reliable and very accurate, but due to ergonomics, manual of arms, and ease of disassembly/cleaning- I must say my Adams Arms P1 Small Frame .308 AR is kinda my favorite.

Left: DB-15 DI AR 300 BLK ; Right: Adams Arms P1 Piston AR .308

 

[Jackofalltrades03]

The rest of the parts are WOA JP Krieger ect. I do run an superlative arms adjustable gas block on the one with the 30 inch bbl.

I don't think I have ever seen anything close to that......WOW