Hi all, I went to shoot my RRA M4 for the first time today. I was using both SA surplus and also winchester JHP. The SA was fine, except for one failure to fire - I guess just a bad round - but the out of 25 rounds of the winchester, 4 rounds failed.  Each time, the bullet had been pushed down into the cartridge. I was using 2 USGI mags, 1 with a green follower that I know for sure I was using when one of the rounds did this, but I'm not sure if these failures happened in the same mag or in 2 different ones. Does it sound like a mag problem, or a bad batch of ammo? Thanks.

Jake

It sounds like a Failure to Feed (FTF).  The magazine is probably at fault, where the rounds aren't stripping straing and clean.  Sounds like they're hitting off center, into the chamber face and pushing the bullet in.  Check your mags and you will probably find feed lips bent or cracked.

Could also be the Jacketed Hollow points not feeding properly into the chamber because of the shape.  They may be getting hung up because the tip is flat.

I dont think they were even leaving the magazine. Ive looked at both mags and there are no bent lips or cracks or anything. I guess I can try changing the springs. If it is the JHPs not leaving because the tip is flat, and assuming the mag bodys isnt at fault, what is the remedy for that? New springs? Just dont shoot them?

IMO, the Winchester JHP that you are using is not suitable for semi-auto use.  That is, if the bullet is being pushed into the case, the bullet may not have a cannelure (groove) in which the case mouth is crimped.  Cannelures and/or pretty stout crimps are used on milspec ammo to prevent the bullet from being pushed back into the case.  IIWM, I'd use milsurp or milspec and stay away from commercial ammo.  If a bullet gets pushed back into a case in such a way that the cartridge can chamber, you can end up with dangerously high KB-like pressures.

Noah

You need to put a few hudred rounds through the rifle (and then clean it) before you decide you have a problem. Hollow points wouldn't be my choice of ammo.

Quoted: If a bullet gets pushed back into a case in such a way that the cartridge can chamber, you can end up with dangerously high KB-like pressures. Noah

Yes this is true...and its why crimping ammo intended for autoloaders is a good idea