308 AR Cycling Issues

[kcstott]

Yeah... if you're having cycling issues, don't get a heavier buffer.

BCG is "bolt carrier group" - i don't know why you'd get a heavier bolt carrier, or even if you can get one.

I had the problem that my AR-10 didn't cycle well after I first built it, too. I had to use a rubber mallet and a tool to get the bolt carrier out of the upper and pull the spent case out.

This is not a chamber issue. This is probably a break-in issue. The bolt and barrel extension probably lock incredibly tightly after a round is fired.

After I cycled the bolt a few hundred times, and managed to get a full 20 rounds through the rifle, it cycled flawlessly. I haven't had a jam since.

I don't think he means a heavier then stock bolt carrier as he had a light weight bolt carrier.

I still don't understand people monkeying with a solid design. Different weight buffers and bolt carriers Captured springs yada yada yada....

Start off with a stock weapon built the way it was meant to be then change one piece at a time as if you run in issues you know very easily what caused it

[bruss01]

I don't think he means a heavier then stock bolt carrier as he had a light weight bolt carrier.

I still don't understand people monkeying with a solid design. Different weight buffers and bolt carriers Captured springs yada yada yada....

Start off with a stock weapon built the way it was meant to be then change one piece at a time as if you run in issues you know very easily what caused it

Thanks, you are correct about the carrier. Originally I was using a low-mass carrier from JP Enterprises. I switched out to a full mass (normal) carrier and the problem changed.

I kinda hear you about monkey with a solid design but I build up my AR's from bare receivers. I don't like to buy a whole rifle and then throw half of it away to replace it with the premium parts I wanted in the first place. With my 5.56 AR's that seems to have worked (or else I got lucky) and it may be because the platform is more standardized.

I honestly don't mind having problems because a gun that shoots perfectly from day one isn't going to teach me much about how and why the guns work and what makes them NOT work. This is part of the learning curve and I welcome it. I'm just trying to tap the collective intelligence of the board here to figure out how to figure it out, LOL. A bit of time, effort and expense goes along with that process, understandably. I'm just trying to minimize the "expense" part at this stage of the game.

[kcstott]

Well I still say shot the crap out of it. It needs to be broke in for sure.

Hand cycling helps but live fire is best and yes that is an expense all by itself

[Marinos]

You need an adjustable gas block. I fought through the same issues you were. I guarantee it's over gassed. Reducing the gas a little will allow the case time to contract making for a clean extraction.

[ar15barrels]

Here's the thing, I think it IS cycling just fine... in fact maybe a bit over gassed for some of the components. Switching to the heavier BCG helped... no more stuck cases. An 18" is not terribly short but it is shorter than most 308 barrels.

I've heard of people having issues like this and a heavier buffer or heavier spring helping. I just would like to try to narrow it down and have a bit more certainty before I lay down $100 for a part and then find out it's not what I needed.

If switching to a heavier buffer helped, reducing the gas flow with an adjustable gas block will absolutely help.
After you have the adjustable block, go back to the low mass carrier and de-tune the gas block some more.

[bruss01]

If switching to a heavier buffer helped, reducing the gas flow with an adjustable gas block will absolutely help.
After you have the adjustable block, go back to the low mass carrier and de-tune the gas block some more.

This is making a lot of sense to me. I believe I will give this a try. The adjustable gas block is useful for fine-tuning anyway so even if it doesn't fix the problem it's probably still a useful upgrade. Thx.

[bruss01]

Gun works now. Adjustable gas block did the trick. Thanks all!

[Dr69er]

AR gas guns in .308's are typically over-gassed (they will usually have larger gas port diameters than needed) thus creating various Issues with cycling, etc...

Most AR 308 barrels will have chambers that were cut and designed for bolt actions or non gas guns (thus resulting in tight chambers and resulting Issues)...

AR gas guns in .308 tend to function best and have the least amount of Issues when using rifle length gas systems (which they were originally designed for, as
was the AR-16/M-16 rifle as well)...

I would also tend to agree with a previous poster to buy mostly stock AR-308 parts from established/well known manufactures to help avoid Some of these
Issues...

Finally, the best Investment in a AR-308 would likely be a adjustable gas block especially if it is a non rifle length gas system...

Good luck to all you AR-308 guys and glad everything worked out for the OP.

[bigbob76]

Start off with a stock weapon built the way it was meant to be then change one piece at a time as if you run in issues you know very easily what caused it

The problem with that approach is that it requires logic and reason.

[bruss01]

The problem with that approach is that it requires logic and reason.

The other problem is buying a whole rifle and ending up throwing half of it away when you upgrade to the performance parts you wanted from the start, and could have built from the git-go. Both approaches work, trade offs are made either way.

[kcstott]

Performance parts.

You mean a High speed price tag...

The real issue is thinking a hodge podge of parts is going to function well together.

Like I said with unproven setup you have to start at ground zero. and you have to know what to look for. Everyone assumes a lack of cycling means under gassed. and in a lot of cases it's the exact opposite. As you found out.

Glad to see you got this puppy up and running.

[ar15barrels]

Everyone assumes a lack of cycling means under gassed. and in a lot of cases it's the exact opposite.

A lot of people would do well to read and REALLY understand this before they go about troubleshooting AR gas systems:

https://www.ar15barrels.com/prod/operation.shtml

[Carcassonne]

Still hoping for suggestions. The thing that leads me to think "heavy buffer" may be the answer is that switching from low mass carrier to full mass changed the problem, lessening the severity. Just looking for tips on narrowing this down, since I don't want to shell out 100 bucks for a heavy buffer if that's not likely to be the issue.

Heavy buffer and an Orange recoil spring is suppose to slow everything down. I have the same problem with my PA-10. I just ordered a heavier buffer, but I have not tried the Orange spring yet.

http://www.sprinco.com/tactical.html

.

[ar15barrels]

Heavy buffer and an Orange recoil spring is suppose to slow everything down.
I have the same problem with my PS-10.
I just ordered a heavier buffer, but I have not tried the Orange spring yet.

Spring tension is actually about the smallest factor in the whole equation.
You could equate changing spring tension with splitting the weights between a standard weight carbine buffer and an H1 carbine buffer, or about the same as switching from an SP1 carrier to an M16 carrier.
Overall, spring changes will make VERY little difference.
Switching buffer weight will have much more effect.

[Carcassonne]

The other problem is buying a whole rifle and ending up throwing half of it away when you upgrade to the performance parts you wanted from the start, and could have built from the git-go. Both approaches work, trade offs are made either way.

Buying a high dollar gun doesn't mean you will get one that works.

Here Nutnfancy talks about his LaRue AR-15 that doesn't work. https://www.youtube.com/watch?v=V_CRqxDLrl4

I purchased Springfield's top of the line (most expensive) National Match M1A rifle. It was a complete P.O.S. Rusty WWII surplus guns with surplus ammo shot better groups than the M1A with Black Hills Match ammo.

I also bought an Olympic Arms upper in the early 1990's that came with a pitted bolt that wouldn't head-space a Clymer go-gauge. I had to machine the bolt myself. It took 2.5 years to get the upper after it was ordered because of Olympic's backlog do to Bush-the-First's assault weapons ban, so I didn't bother to complain or return it. I was just happy to finally get it. The rest of the rifle worked great, and I still have it today.

My PSA PA-10 308 is having problems. I knew it might since I did some research before I made the purchase. I am having the same problems as everyone else. I do not feel like sending it back because in single shot mode (as opposed to semi-auto from a magazine), it has better accuracy than I expected. As long as the barrel is accurate, I can fiddle-fart with the other stuff to make it work.
So far I have replaced the extractor spring ($2), cut 2 coils off the ejector spring, and purchased a heavy H3 buffer ($40). I have also purchased a NBN fire control group ($35) even though I didn't need it. I needed a new hammer and trigger for another AR, so I just decided to pay a little more and get the NBN group, install it in my PA-10, and then install the old PA-10 group in the other rifle. I bought a 1/4-28 tap ($5) and some set screws ($1) so I could make a poorman's set trigger. I also purchased Magpul buttstock, grip, and handguard because I didn't like the original ones. I have a little more work to do on the rifle before I am finished with it. I may also have to buy the Orange spring in the link above.



.