My Bushmaster Shorty AK frequently short-stroked through 700 rounds of PMC and Winchester (white box, 55 grain). Had several short-strokes per magazine up through about 300 rounds, and about one per magazine through 700.
This occurred regardless of the magazine used. All of my mags are GI issue, black and green follower, except for a couple of Thermolds.
I'll keep it nice by only saying that I was [b]very[/b] disappointed [:(!] .
As I got around the 700 round count, I discovered AR15.com. Normal lubrication did no good, so after reading the troubleshooting section I tried Tetra grease on the carrier, which was a disaster.
Finally I clipped one turn off of the buffer spring and ran 300 rounds through in one sitting with about 2 instances of the bolt not locking back, but NO short-strokes [:D] .
That was the last time I've shot it, as I transferred here to Korea.
I've got both of my AR's here with me now, and should be taking them to the M16 range next month, and I don't anticipate any problems.
Chris