Home Forums Hunting & Shooting AR and Tactical Rifles AR10 cycling problems with suppressor

I've been running a Christensen CA10 308 for almost a year now, and it's a sub-moa rifle all day long. It was overgassed from the factory, so I dropped a superlative arms gas block on it (i had a suppressor on order) and it quit destroying my cases. I recently received my SilencerCo Omega suppressor, and that's when my serious woes appeared.

The superlative arms block is supposed to have a blowoff for running suppressed. Essentially, the first 4.5 turns are standard block restriction, and anything beyond that blows gas out the front so it doesn't come back in your face. it's supposed to be the bees knees when running a can. BUT, even at full blowoff, I'm still getting massive overgassing. I can run restricted to a tolerable degree, but it's not 100% reliable suppressed (I either eject to 1 o'clock and ejector stamp my brass, or eject at 4 o'clock and get a jam every mag). I've yet to get any response from the mfg.

So my current plan is a Sprinco Orange spring, as it seems that increasing buffer pressure should decrease the overgassing problem I'm having. I also think I need to drop spacers in the buffer tube, as the bolt opens nearly .5" past the bolt catch, and broke the catch last week while I was testing my block suppressed.

Has anyone fought this fight before? I'm relatively new to AR's. This is the only one I've owned, and it's the first time I've shot suppressed. I'm really trying to make it run like a top (I have a bet with a friend that I can make it through a 3gun match, suppressed, without a jam) but I'm not sure i'm on the right path. Any guidance from the masses?

I've been through that before and spent a lot of money to find out what works. The adjustable gas block helps but doesn't completely fix the issue. You need more weight in the recoil system (carrier, buffer, spring). My issues were fixed by the Tubb carrier weight system (tungsten), Tubb AR-10 recoil spring, and a heavier buffer. Not sure which BCG they use but if its a "low mass" bolt carrier, that will not help the situation either.

Basically you want to do whatever it takes to delay unlocking of the bolt and slow down the carrier during cycling.


Oh, and did you say MOA all day long?

https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/9834630/1

Thanks wareagle. I'll look into the tubb gear today. Any thoughts on what spacers to use? Or will a new buffer fix that issue (I'm assuming a longer buffer would stop the bolt from moving so far back into the tube)?

And thanks for the link! I've been running a red dot on the rifle, but my scope mount should be here this weekend. Far easier to get solid groups when your sight doesn't cover most of the target lol. I'll have to print out a few of those targets and see what I can do.

I've been there as well, but fixed it with a better gas block. Mine runs 100% even with a lightweight carrier and carbine buffer; I didn't find any need for heavier weight in the recoil system once the gas was tuned correctly. First thing - get a simple screw-adjustable gas block, with no clicks or that stupid bleed off system. Something like the Seekins block, where adjustability is infinitely variable between full closed and full open.

Yondering, I've read that screw type blocks have a tendency to freeze up when they get hot and dirty. Have you dealt with that at all?

So.... The Tubb carrier weight system has been discontinued. It looks like I'm going with a Sprinco Orange spring and a spacer (I may start with a stack of quarters first) to see if that helps me any.

All the better, I don't want the adjustment to change.

I frequently change between suppressed and unsuppressed, so I need to be able to alter mine back and forth.

Why would you use a spacer?

The bolt moves past the bolt catch by about half an inch. Apparently, when they overrun the bolt catch, they get a running start when they come back and hit it, and it's the primary cause of broken bolt catches. A guy at my last 3gun shoot told me to find a spacer to drop in the back of the buffer tube so that the bolt could only come as far as it needed to clear the bolt catch but no more.

Are you by chance running a carbine buffer in a rifle tube?

I am running what the factory put in. I'm not sure what you're asking. I know the buffer is 2.5" long and it's in a collapsible Magpul ACS stock, but that's all the factory gear.

I do as well, and don't need to change anything. I have the rifle tuned to function on full power loads (it won't cycle most mil-spec stuff), and it ends up slightly overgassed with the suppressor on but not too bad and function is 100% both ways. That's with a bolt carrier that's 1/2 oz lighter than an AR15 full auto carrier, carbine buffer, and standard spring; no problem at all when the gas is tuned right. It's an 18" barrel and rifle gas btw; a shorter gas system may have more trouble.

If you want the rifle to run both mil spec and hotter loads in one setting, you'll have a lot more trouble when adding a suppressor in the mix too.

Also, keep in mind that some 308 AR setups use longer buffer tubes and standard buffers, while others use standard tubes and shorter buffers. Don't mix and match between those setups. You may have a long tube and short buffer. (When I say "standard" I'm referring to mil-spec AR15 dimensions.)

One more thing to consider - a lightweight carrier is a lot easier on the bolt catch. Standard 308 carriers are massive, and all that reciprocating mass does make them harder to shoot well IMO; adding heavier buffers and stronger springs does not help either.

Ok if you have a collapsible stock then it sounds right. I just have never heard of a spacer for inside of a tube, there is one for A2 stocks that goes on the outside but that's all I've heard of. The bolt catch should not touch the BCG until the mag follower pushes it up. I've seen one break and it was cast, put in a mil spec catch and never another problem.

A big +1 to all of that.

I wouldn't worry about that with your rifle unless its been a problem. 3 gunners have lots of tricks up their sleeve but not all of them are universal or beneficial for all setups.

This has not been my experience, especially with a can on the end.

More mass keeps the bolt in battery longer which means less movement while the bullet is in the barrel. This is even more important for guns with short gas system lengths and over sized ports. It also further allows for chamber pressures to drop so extraction is more reliable. With a lightweight carrier, I experienced more damaged brass, bent case rims, and bolt speed was so fast it occasionally led to feeding issues as the bolt would out run the magazine spring.

There is a reason JP (traditionally a 3-gun company) came out with a FMOS carrier for large frame AR's and it wasn't to decrease reliability. You can absolutely make a 308 run with a lightweight carrier though, I won't argue that. I just found that more mass in the recoil system made my rifle more reliable, forgiving, and accurate with a suppressor and different loads.

Here's a good article for large frame 308's.

https://gunsmagazine.com/big-chassis-ars/

I already broke one bolt catch. I was trying to get my gun gassed down to where it wouldn't lock open (per instructions by the mfg of my gas block) and it was an hour or more of constant locking open on an empty mag. The guy i shoot with is a local gunsmith who gave me that advice. It made sense given the circumstances.



This tracks with what I have seen with this rifle. it's always been overgassed, and had a serious problem with coming out of battery while still under pressure. I was stamping case heads and had expanding necks to a degree i'd never seen. And thank you for that link; I'll look into it after the steel match tomorrow

We've discussed this before, but restricting the gas correctly also keeps the bolt in battery longer, without needing to add extra mass. It doesn't matter if the gas port is oversized or not when you tune the gas correctly with an adjustable gas block. From what I read, I'm pretty sure most who have issues are not doing that part correctly.

I just have to shake my head when so many people have problems tuning these but won't listen to those who've been successful. I use mine under all the conditions discussed above, including very hot loads (which so many "experts" claim 308 ARs can't handle), and never have issues with mangled brass, swipes, stamping, or anything else; 100% function all the time with the loads it's tuned for. A couple others I've tuned for friends have been the same way; it just doesn't have to be that hard and there aren't any secrets, just a lot of bad information out there from supposedly "reputable" sources.