John Many years ago I shot a MK II bull barrel a LOT. I would shoot it until it hung up, usually about 1500 shots, hose it out with brake cleaner, squirt some WD 40 in there, and go back to shooting. I don't believe I ever disassembled the gun.
This was using Aguilla ammunition, which was very dirty, but shot really, really well. Put many cases of shells through that little gun.