I picked up a G22 .40S&W over the summer and have been shooting it every weekend in IDPA matches. I reload the .40S&W and have been all along. I had something strange and scary happen at today's match. Half way through the 3rd stage I pulled the trigger and immediately felt a sting on the inside of my right hand. I looked down and the magazine had been blown out the bottom of the gun and a piece of the magazine release fell onto the ground. I was not cut or hurt except for my pride due to my shooting buds thinking it was a double charge. I don't think it was a double charge since 2x the powder will not fit into the case. The report and recoil felt a little weak. I'm wondering if this is a case head separation. I had one case in this batch of brass that showed cracking and separation. I'm not sure if this is how the gun would react to a case head separation and thoughts? The load used was 4.5gr of Red Dot (max in Alliant manual is 5.1gr) behind a 170gr round nose bullet.