what would happen?

[Sheldon J]

45 acp is a rimless cartridge are you meaning being too long to headspace properly.I just looked the GAP is a lot shorter and has a thicker case wall due to higher pressures it looks like it will fire but probably jam in the gun,some people were thinking about cutting down 45 ACP brass to reload for 45 GAP but thats looking for a kaboom due to the thinner case and higher pressure of the gap cartridge do not do it you could seriously injure yourself or others

Let me give you the condensed version, the GAP round being shorter but basically the same Dia. chambered and fired in the ACP pistol (by accident). However due the the fact that a ACP round has a larger rim and is longer I would bet that you could not get one to either feed or fully chamber in a GAP pistol

[DefensiveCarry.com]

[anautical45]

I have one for ya!

Just after I got my Pro CDP II. I was at the range for the 2nd time with it and had my son with me. I was letting him put some rounds thru it and he needed more ammo. I gave him 20 bucks and he bought a box and came back and started shooting. He got over 40 rounds of the 50 and the gun FTE a couple and came over and ask to see what was going on. He had fed a whole box of 45 Gap thru the gun with no problems. The range officers were all amazed and the inhouse gunsmith could really believe it fired with no problems until the end. Didn't hurt the gun. Still works 100% today.

Steve