Right now, I have only 3 carbines, but I've had as many as 14 at one time and used the same reloaded ammo in all of them. As long as the case was within spec for case length, there was no problem in any of the carbines. I didn't even have any problems with cases that were a bit short since with the tapered case, the cartridge will often not reach the front of the chamber before the sides of the case stop it. The only "problem" I ever had was with one particular Saginaw that must have had a rough gas port. It would accumulate lead in the piston chamber and needed to be cleaned every 3-4 hundred cast rounds. None of the other carbines that I've owned ever had that problem. I should note that I've owned and shot 28 of them including a full auto M2. And yes, I even shot cast in the M2 without problems.