13.7 issue

[greene]

Just put a new upper together. 13.7 stainless mid gas barrel, kit came with a bcg & gas block/tube. Using a H buffer & carbine spring. Went to do a quick zero, locked bolt back, inserted mag, hit bolt release, round did not fully chamber. Pulled out mag, round then chambered completely. Fired mag until empty & got lock back, put in fresh mag, hit the bolt release & the same sequence happened. Ammo was steel case brown bear. Mags were usgi loaded to 28 rounds. This happened with & without a suppressor on. Any thoughts? Thank you

[gaijin]

I’d try some brass case ammo. See if problem continues, or disappears.
I would guess a chamber issue if brass case ammo chokes as you describe with steelcase.

[Clint]

So it won't feed steel case ammo from a USGI mag and bolt lock.

Could be a friction issue of too much drag or not enough spring.

Inspect the feed ramps for any potential hangups.

Narrow down variables.

Try slingshotting the charging handle vs using bolt release.

Try 10 rounds loaded vs 28.

Try brass ammo vs steel case.

Try a PMAG.

Try a new spring.

[1168]

Inspect the feed ramps for any potential hangups.

See if they’ll grab a q-Tip. Particularly the right side one, if the top round in your mag is on the right.

[georgeib]

In addition to the suggestions already in the thread, make sure that the BCG is sufficiently lubricated. This is even more important for a new build.

[17K]

I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.

[1168]

I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.

Funny you should mention that. I actually had some problems today with some metal mags if unknown manufacture. Some barely held 30, some only held 29 (damaged lips implied, but not really looked at). With my full-time suppressor host and its heavy-ish spring, I had trouble getting the first round to strip without the push-jerk inertia trick. The BCG was clean-ish and lubed.

There may be something to be said for the top round having a little space, and PMags do that, for sure. I never have trouble with my own GI mag collection, though.

[Clint]

Agreed, the top round of 30 certainly needs room to push the stack down as it pivots.

The OP was downloaded to 28, so probably not that issue in this case.


Funny you should mention that. I actually had some problems today with some metal mags if unknown manufacture. Some barely held 30, some only held 29 (damaged lips implied, but not really looked at). With my full-time suppressor host and its heavy-ish spring, I had trouble getting the first round to strip without the push-jerk inertia trick. The BCG was clean-ish and lubed.

There may be something to be said for the top round having a little space, and PMags do that, for sure. I never have trouble with my own GI mag collection, though.


PMAGS certainly feed rounds higher and with less friction.

Yes, this can eliminate feed issues in many cases.


I have encountered this quite a few times with a new build, especially if using brand new g.i. mags. I think it’s just a friction issue as everything is all brand new.

One thing I have found, and one of the reasons why I exclusively use them, is that you can change nothing but the mag and it will feed with a Pmag.

[greene]

Cleaned barrel & chamber. Put it on a lower with an A5 system. Problem went away. Shot steel & brass from usgi & pmags fully loaded. Thanks

[Glock9mm1990]

What mags where you using?

[Disciple]

OP reads
Mags were usgi loaded to 28 rounds.