[taylor6400]

I have a build (my first) that i think has a slight problem somewhere. It shoots and runs all my mags fine. But it wont lock open on an empty mag. I can manually lock it, and if i pull the bolt open slowly on an empty mag it will catch. But normal shooting or quick cycling and it wont catch. Is there something i can adjust? ITs almost like the mag spring is not quite enough to get the bolt catch high enough. But they are all pretty new Pmags. Suggestions?

Thanks

 

[Quickdraw Limpsalot]

One of three problems.

a) Your magazine follower and/or spring are worn/weak (Does it happen with multiple mags?)

b) Your mag catch is broken/flawed (New gun?)

c) You're gun is short stroking. The bolt carrier group is coming back far enough to eject the spent casing, but not far enough to clear the bolt stop.

It's most likely the mags, or plain ol' dirt.

 

[thisismyusername]

Quickdrawn has some good suggestions.

OP, what weight buffer are you running? What BCG are you running? As far as the short stroke, you might have to experiment with different buffers to address.

 

[John A.]

The Pmags I have, occasionally will not lock the bolt back when empty. Especially that straight 20 rounder I have.

GI mags work, without fail.

Aside from the earlier recommendations, there may be some excess anodizing, or tight restriction preventing free movement of the bolt stop as well.

Or too heavy of a buffer or buffer spring steamrolling over top of the stop on its' forward movement.

 

[taylor6400]

Im not even sure of the buffer weight actually. I bought the Spikes complete middy upper with BCG, buffer and spring. I have the other buffer my Magpul stock came with. I will try GI mags with current buffer first and then try changing the buffer and see if they work ont he pmags. I dont think its short stroking though as if i just rack it on an empty mag it wont catch unless i go slow. I will try the GI mags...the Pmags are almost new so maybe there is just a slight flaw with Pmags.

ETA: I have a Spikes lower and a Stag LPK FWIW

 

[Quickdraw Limpsalot]

So how many Pmags are you having this problem with? How many have you tried? As John A. mentioned, is there any crud around the bolt stop? Does it move freely?

You apparently have a bad follower, weak mag spring, or sticking bolt stop (assuming the geometry on the bolt stop is good - I've seen bad bolt stops missing the part that is pushed up by the follower straight out of new parts kits.)

 

[taylor6400]

So how many Pmags are you having this problem with? How many have you tried? As John A. mentioned, is there any crud around the bolt stop? Does it move freely?

You apparently have a bad follower, weak mag spring, or sticking bolt stop (assuming the geometry on the bolt stop is good - I've seen bad bolt stops missing the part that is pushed up by the follower straight out of new parts kits.)

I only tried 2 mags because thats all i shot and the rest are loaded. Its not crud...its a brand new build. Maybe things just need to wear in a bit. I will get out this weeknd and run a couple GI mags through it and a coupel more Pmags and see what happens.

On the flip side...my first build seems to run well with this exception.