You never did say exactly what you're shooting but I have a Mark I that had feed problems and after having a gunsmith strip and clean it and still having the same problems I replaced the magazine which cured it. Seems the spring was weak.
It's a Mk II Government Model. It's just something that it's always done. I bought it back in 1989, and it's done it since day one. I've tried different magazines, cleaning methods, solvents, lubes, etc... I guess it's just part of the "personality" of the gun. No big deal. I just make sure that once I've given the gun a good cleaning that I put 100 rounds through it before using it for competition. It's no big deal. After that 100 round guestimate, it NEVER jams. I couldn't even begin to guess how many rounds I've put through it: At least 100,000 rounds, and that's just how it is.
Mark