Good evening All, got a question for you regarding AR15 magazines.

I have a DPMS rifle, and I have 5 magazines for it, 4 MAGPUL, and the metal one that came with the rifle.

The issue is that when the last round is fired from any of the magazines, the bolt does not lock to the rear, it slams forward onto an empty chamber.

Not sure if this is a magazine or a rifle issue. Anyone else ever run into this.

The rifle is brand new, only about 200 rounds through it.

Look forward to any and all ideas and suggestions.

What ammo are you using and did you do a thorough cleaning/lubing before firing it?
Tomac

Your weapon could be doing 2 things, short stroking or the bolt catch isn't engaging.

If it's short stoking, there's not enough pressure to fully send the bolt to the rear.  There might be enough to strip new rounds off and keep it cycling, but not enough to engage the bolt catch.  Try using some 75gr 556 to see if it helps at all.  You could also change to a lighter buffer or clip the spring a couple links.

If the bolt catch isn't engaging (My personal prediction), then what's happening is that the magazine follower isn't fully engaging the bolt catch and it's not raising enough to stop the bolt from slamming forward.  This could be caused by friction between the lower/boltcatch/rollpin that's fighting the force from the mag follower, or by the bolt catch having too short of an arm.  The follower is coming up, but the bolt catch just slides around/over it and stays down.  My friend fixed his by using Hexmags; they fit a little tighter in his magwell and was able to hit his shorter arm.  Or, brownells has extended bolt catches that you can file to size.

9mm bolt catch

Let us know how it goes.

What I would do is first
With an empty gun, pull back on the charging handle fully to the rear and manually engage the bolt stop.  Does the bolt stay to the rear?

If so, Put an empty mag in the firearm with the bolt closed.

Pull back on the charging handle and let it go.
Does the bolt lock back?  If it does, it's an ammo problem with short stroking.

If it doesn't look to see if the follower on the mag engages the bolt stop

Follow the instructions to ensure proper cleaning and lubrication (slightly heavy on the lube, especially when new).  Test fire with new brass cased ammo and Pmags.  If it still fails, call for factory support.  Do not change or modify anything, or there is a high likelihood that you will not get warranty work done.

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