I visited one of the best gun shops in my part of the state this week and during the time there, my friend who is not only a salesman, but the shop's gunsmith, asked ME if I'd tried shooting a .45 GAP round from a.45 ACP Glock pistol! He stated that, while he hadn't tried it himself, he was sure it would work. I replied that I had not even considered doing so. He is much more knowledgeable about all things Glock than am I! I only know definitely that .45 ACP WON'T work in a .45 GAP, but what ABOUT the reverse?