When I first bought the 39 I shot it stock without problems. After I put the pierce +1 on both mags I have a problem with one of them. First off, they both shoot and feed perfectly when I'm putting HST's thru them. But the problem starts when I shoot federal american eagle target rounds, 185 and 230 grain. The one mag has a problem feeding the last round in and its always the last round, the other mag hasn't had a problem, and remember both have the pierce +1 on. Wierd also is sometimes that last round will spit out completely and when I pull the trigger it goes click with the slide forward, the first time that happened I thought it was a failure to fire but when I looked in the round wasn't even in the chamber, and I look on the ground and there it was. I'll be returning that mag to stock, but wasn't sure if you guys have heard of this.