308 Mag Issues

[Ljapilot]

My 308 gas gun runs great and has no issues when using Knights 20 round magazines. When I swap to a Magpul or Lancer 20 I get numerous failure to feed. The bolt ends up over the back of the case with the bullet jammed. I would write it off as a magazine but I’ve tried multiple Magpul and Lancer mags. I am shooting M118LR and 168/175 FGMM. This occurs normally with a low round count in the mag but not exclusively. Also, never an issue if cycled by hand.

Any ideas what would cause this would be appreciated. I would like to be able to run the “cheaper” mags reliably.

 

[LRRPF52]

Talk to me more about this .308 gas gun.

 

[Ljapilot]

Talk to me more about this .308 gas gun.

What more would you like to know?

It is a Lanxang VL34 20” 308. All is factory except the buffer. I put a slash’s heavy buffer in it.

 

[LRRPF52]

Any reason you changed the buffer from a company that makes a $3600-$3800 rifle?

Maybe they know what makes it run reliably and it doesn’t need the buffer replaced?

On their site, they show the rifles with Magpul 7.62 NATO PMAGs.

Put the original buffer back in it, and see what happens with PMAGs.

I’ve seen large frame .308s that wouldn’t run on PMAGs, switch to Lancers and they ran like raped apes for 2 days straight of shooting.

 

[Jsp556]

They make guns that run 35k rounds without cleaning, on the original barrel, and still deliver 1/2 moa accuracy with off the shelf ammo. How tf are you having issues? Lol

I’d put the factory buffer and spring back in it.

 

[Jgault]

308’s are just finicky AR’s. I have one that will run on every mag I’ve tried, my other with one bolt carrier(2a armament) will run all mags, then if I change the bcg to Faxon it will do the same as you described with Magpul mags but run on everything else I have. Because 308’s aren’t made to a universal spec every part from different makers can be a little different. The problem (I think) with the Faxon bolt in mine is the lugs are a slightly different shape combined with the pmag sitting slightly lower and looser than my other mags causes the malfunction.

 

[Ljapilot]

Any reason you changed the buffer from a company that makes a $3600-$3800 rifle?

Maybe they know what makes it run reliably and it doesn’t need the buffer replaced?

On their site, they show the rifles with Magpul 7.62 NATO PMAGs.

Put the original buffer back in it, and see what happens with PMAGs.

I’ve seen large frame .308s that wouldn’t run on PMAGs, switch to Lancers and they ran like raped apes for 2 days straight of shooting.

I put a heavy buffer in it to tame it being overgassed. They make the gun where it will run any ammo. The M118 and FGMM was way overgassed then add a suppressor. I wanted to cut the gas and recoil.

The gun runs great on the kac mags. No issues what so ever. It’s only the pmag s and lancers.

What was the issue with the rifle you mentioned? Why didn’t it run on pmags but was fine with lancers? That’s the information I’m trying to find out.

 

[hlee]

You got the money for a $3600 rifle. Buy a pile of KAC mags and call it a day...

 

[FCS]

My 308 gas gun runs great and has no issues when using Knights 20 round magazines. When I swap to a Magpul or Lancer 20 I get numerous failure to feed. The bolt ends up over the back of the case with the bullet jammed. I would write it off as a magazine but I’ve tried multiple Magpul and Lancer mags. I am shooting M118LR and 168/175 FGMM. This occurs normally with a low round count in the mag but not exclusively. Also, never an issue if cycled by hand.

Any ideas what would cause this would be appreciated. I would like to be able to run the “cheaper” mags reliably.

KAC allows for a slightly longer OAL.
M118LR might actually be dragging slightly in MP or Lancer mags, causing delay in getting round up for bolt to catch. Gen2 MP mags are a little longer inside than Gen 1. Lower round count, less pressure pushing up the round...

Best wishes on troubleshooting the issue.

 

[Ljapilot]

@Jgault and @FCS thanks for the info.

@Jsp556 I’ve shot that rifle. Don’t know what the round count is but is was 3/4 MOA rifle for me. Their rifles are very impressive. Good group of guys that work there as well. I will always recommend them.

@hlee that is plan B. Just looking for info on ways to maybe not have to do that. 3.6k on a rifle is one thing 1k on mags is completely different in my mind.

 

[LRRPF52]

I put a heavy buffer in it to tame it being overgassed. They make the gun where it will run any ammo. The M118 and FGMM was way overgassed then add a suppressor. I wanted to cut the gas and recoil.

The gun runs great on the kac mags. No issues what so ever. It’s only the pmag s and lancers.

What was the issue with the rifle you mentioned? Why didn’t it run on pmags but was fine with lancers? That’s the information I’m trying to find out.

Polymer mags have thicker feed lips so the cartridge in-presentation sits lower than metal mags.

Metal mags have different feed lip angles and dimensions specific to how the rim is positioned, and how the hand-off of the cartridge from the magazine is controlled as the projectile rides up the feed ramps.

If the angle is too much as the cartridge is being pushed up the feed ramps, you’ll get FTFeed.

PMAGs in certain receiver sets place the cartridge presentation lower. They’ve gone through several iterations of 7.62 PMAGs. I have the 1st Gen versions which run like raped apes in my .260 Rem that GAP built for me many years ago.

You can also try the IMI 7.62 mags.

 

[Ljapilot]

Seem to of found something that works for now. It would seem the nose was sitting too low. I put a small pad on the back of the mags and 100 rounds later no more issues. Going to get a couple more hundred rounds before I look for a permanent solution.

strange how such a small thing can make a world of difference