A few years back, I built a 9mm upper and used endo mags in a poverty pony lower. Due to problems with the barrel, I had three kabooms that destroyed three of the endomags.
Because they were a relatively new item at the time, they asked me to send them in so they could see how they held up. All three kabooms blew the base off of the pmag, and cracked the magazine bodies. They then sent me new pmags and endomags to replace the destroyed ones. Just to make some ARFCOM understands, it was a short chambered 9mm barrel that caused the Out of Battery kaboom and had nothing to do with the endomags. Once the barrel was replaced, the gun ran fine without any problems. I wish they would make endomags in 45 acp.