Thanks for reaching out Jeff! Gosh, the only explanation that comes to mind is that they accidentally sent you 45 ACP which is 0.205" longer than 45 GAP, but I'm certain you would have noticed that kind of mix-up. Buffalo Bore loads to SAAMI specs, so their ammo should by all means chamber in a Glock. I suppose a grave manurafturing defect or some extreme damage during shipment could have caused the bullets to creep forward in their cases, although that seems unlikely. It's all just conjecture anyway since I can't observe the FTF. I'd definitely reach out to Buffalo Bore if I was you – they ought to have greater insight than I can offer. Wish I could be of better help!