After many thousands of rounds of heavy loads they will start to go out of time. This means the cylinder won't quite come up to perfect alignment with the forceing cone of the bbl...

Trust me, they aren't "nearly" as fragile as james is implying. "If" they were, i'd have shot a dozen of them to junk long ago!! I have two M-29's that are dash 2 series,that i bought new. Do you know how many years old that makes them? Both are still tight and still shoot excelent!

Drilling Man