Gulp. Found out my AR-15 wouldn't feed hollowpoints too well...

[stubbicatt]

How is there a mismatch between the barrel extension feedramps and the receiver? It is a rifle style ramp, not a mismatch, at least not that I can see.

OP. Seriously, for $12 you can buy a PMag. Try that first?

 

[M1key]

I would touch-up the feed ramp and try P mags.

M

 

[MistWolf]

Good grief! The ramps are not FUBARed, they are simply mismatched. What Stress_Test has is a barrel with M4 ramps mounted in a rifle upper.

Before attempting to cut the upper to match the barrel extension, know what you're getting into. It will be very easy to slip and gouge something or make the cuts too deep, too wide, the wrong angle or any or all of the above.

It would be simpler (and not very expensive) to get a stripped upper receiver cut to match the M4 ramps and swap the barrel over. The rifle upper could be sold to recoup some, if not all, of the cost. If you have the tools or can borrow them, mounting a barrel to an upper isn't difficult. Another option is to find someone nearby who has the tools and experience and show up on their doorstep with rifle & parts in one hand and a pizza & drinks in the other

http://www.bravocompanyusa.com/AR-15-Upper-Receiver-s/33.htm

 

[M1key]

Try Pmags first.

I would not use a Dremel. A few passes with a rat tail file and polish with a little emery cloth.


M

 

[3twelves]

Good grief! The ramps are not FUBARed, they are simply mismatched. What Stress_Test has is a barrel with M4 ramps mounted in a rifle upper.

Before attempting to cut the upper to match the barrel extension, know what you're getting into. It will be very easy to slip and gouge something or make the cuts too deep, too wide, the wrong angle or any or all of the above.

It would be simpler (and not very expensive) to get a stripped upper receiver cut to match the M4 ramps and swap the barrel over. The rifle upper could be sold to recoup some, if not all, of the cost. If you have the tools or can borrow them, mounting a barrel to an upper isn't difficult. Another option is to find someone nearby who has the tools and experience and show up on their doorstep with rifle & parts in one hand and a pizza & drinks in the other

http://www.bravocompanyusa.com/AR-15-Upper-Receiver-s/33.htm

You are making mountains out of mole hills....

 

[michael5446]

polish all feed ramp edges with the dremel... once brass gets marred or chewed up on the way in you are pretty much doomed...

 

[Walkalong]

It would be simpler (and not very expensive) to get a stripped upper receiver cut to match the M4 ramps and swap the barrel over.

This is easy, and would improve chances of feeding, but the M4 barrel extension mated to a standard upper ("OK" in the pic on page one) is really no worse than a standard extension mated to a standard upper.

Try different mags first.

 

[Stress_Test]

UPDATE:

Ok, I think I may have an answer, or at least part of an answer.

I got some dummy function-check rounds so that I could cycle everything without chambering live rounds at home. I tried it first with one of the AR-Stoner mags that was already loaded. I put the 4 dummy rounds in to top off the mag. I cycled these 4 dummies through the action multiple times, both using the bolt release and also pulling the charging handle back and letting it fly. No problems there.

I tried it with the other AR-Stoner mag, which was empty (I didn't load it up because earlier I had already managed to slice my index finger on the sharp edge of the mag lip of the other mag! ) so this 2nd mag only had the 4 dummy rounds in it.

I released the bolt on the first round, and it chambered ok. I ejected that round, and let the bolt fly forward again. It jammed this time. The round had only come partway out of the mag, and the bolt had jammed against the side of the round, a little bit before the neck/taper of the case. I cleared that jam, and the last two rounds fed okay.

Further investigation of the mag revealed that the feed lips (?) may be too wide apart, and possibly the mag body itself. When I push down on the four loaded rounds in the mag, the top two rounds almost try to go side-by-side instead of remaining in a staggered stack. (the other mag didn't do this).

I tried again, this time slowly opening and closing the bolt by hand so I could observe what was happening. It appeared that as the bolt slid back over the next round in the mag, the round would flip up at an odd angle and not stay down in the mag. Letting the bolt forward slowly, sometimes it would catch the round correctly and guide it to the chamber. Other times it would ride over the top of the round and cause a jam (I assume because the rim of the round was angled downwards too far when the bullet was flipped up). Also, on two occasions, the last round in the mag would pop completely free of the lips when the bolt came back; the follower would hold the bolt open and the round would be lying loose in the receiver. I think this may explain how some of the jams occurred where the tip of the bullet nose-dived in front of the ramp and stopped: If the round popped completely free, it could've been lying on top of the magazine pointing downward when the bolt came forward again.


So hopefully I've found the problem. It'll be a while still before the range opens again for me to confirm. I can let someone else use this mag in their AR, and if they start having jams, I think that'll be the clincher.

The bad part is, it may be hard to find anymore new mags now!!

 

[rcmodel]

I was thinking we said bad mags in posts #2 - #6?

rc

 

[David E]

LUBE it!!

 

[Stress_Test]

I was thinking we said bad mags in posts #2 - #6?

rc

Conventional wisdom and experience wins again!! Who wudda thunk it!?




Too bad I already Dremel'd everything and changed the barrel, the upper, the lower....



JUST KIDDING!!


Anyway, I don't know if this is truly the answer until I shoot it again, but it sure looks like part of the problem at least. I'm pretty sure the mag shouldn't behave the way this one does.