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View Full Version : Feeding issues on new CMMG Spr Upper


jerryballs
05-02-2008, 3:40 PM
So just got a CMMG upper from a friend of mine and it worked great with xm193....But when I added the green tip 855 stuff it would fire the first round, eject the casing and reload nothing into the chamber...I thought it was the mag, but I changed that out and it continued to do it only with the xm855 stuff...

Any ideas? I am going to try a different BCG when I have time...but I was totally confused...

I tried searching but couldn't find much..

Thanks in advance

Jerry

Sgt Raven
05-02-2008, 4:24 PM
So just got a CMMG upper from a friend of mine and it worked great with xm193....But when I added the green tip 855 stuff it would fire the first round, eject the casing and reload nothing into the chamber...I thought it was the mag, but I changed that out and it continued to do it only with the xm855 stuff...

Any ideas? I am going to try a different BCG when I have time...but I was totally confused...

I tried searching but couldn't find much..

Thanks in advance

Jerry

Do you have a rifle or carbine buttstock? If you have a 'heavy' buffer it might be short stroking.

aplinker
05-02-2008, 4:33 PM
Yeah, if it's a heavy buffer it could be an issue. Mid-lengths don't need the carbine fixes.

Try loading one round and see if the bolt locks back - that's pretty much 100% short stroking.

Sgt Raven
05-02-2008, 4:47 PM
Yeah, if it's a heavy buffer it could be an issue. Mid-lengths don't need the carbine fixes.

Try loading one round and see if the bolt locks back - that's pretty much 100% short stroking.

Or sometimes a Ďenhancedí BCG can cause problems too.

+1 on single loading and see if the bolt locks open.

jerryballs
05-02-2008, 6:28 PM
so with one loaded the bolt will not lock back after it fires... It just stays closed.

My stock is a magpul ctr carbine stock.... Is that the problem?

Sgt Raven
05-02-2008, 9:24 PM
so with one loaded the bolt will not lock back after it fires... It just stays closed.

My stock is a magpul ctr carbine stock.... Is that the problem?

No, itís the power of the load. Since your rifle functions fine with XM193 then either the XM855 is loaded weak or something is slowing down the cycling of the action. It can be the wrong buffer, an enhanced BCG, or a under powered load. If you had a rifle buffer tube, spring, and buffer then Iíd say a weak load. Or even not enough lube, AR15/M16 run best when run wet. You can't use to much lube on the BCG as any extra will be blown off.

jerryballs
05-02-2008, 9:37 PM
No, itís the power of the load. Since your rifle functions fine with XM193 then either the XM855 is loaded weak or something is slowing down the cycling of the action. It can be the wrong buffer, an enhanced BCG, or a under powered load. If you had a rifle buffer tube, spring, and buffer then Iíd say a weak load. Or even not enough lube, AR15/M16 run best when run wet. You can't use to much lube on the BCG as any extra will be blown off.

That's great info... Thanks

When you say "enhanced" BCG, what does that mean?

Thanks
j

vega
05-02-2008, 9:50 PM
Bolt Carrier Group.

jerryballs
05-03-2008, 7:12 AM
Bolt Carrier Group.

right but what does enhanced mean?

Red_5
05-03-2008, 11:35 AM
"Enhanced" can mean a lot of things, but in the context of this discussion, heavier than standard.

Your trouble is most likely weak ammo if it runs fine with ammo other than the stuff that doesn't cycle.

scfast
05-03-2008, 11:45 AM
Sounds like short stroking maybe under powered ammo...make sure your running it wet i had no problems w the xm193 either. I did shoot it dripping....we are running the same stock and and also the buffer i presume.it's not the bcg.