Very diry ammo. For instance, my brother shoots with Wolf, I will use anything else (PMC, Federal, Winchester, etc). Both of us will fire 150 rounds through a clean rifle. His rifle will have a bunch of red and green flakes all in it, and also a bunch of black soot or whatever it is. My rifle will be basically clean. I can imagine after 500 or so rounds his rifle would be jamming due to all this crud that is clogging up his chamber and action. I'd shoot it if I was super broke though, and not worry about it, but as long as I have a few extra dollars I think that other ammo is better for that reason.