Originally Posted by RidgeRanger
Looks like intentional bullet crimp marks on the case mouth to me. Is the bolt hard to close? It would be crazy hard if the case neck was all the way into the rifling, plus you'd have several other problems. As for the cracks, crappy Winchester brass would be my first guess. Try some different ammo.

That was my first thought too, seen some LC 7.62 brass with crimps just like it. Was this ammunition older or new? I've had older winchester brass crack and split in 22-250 with just a few loadings. Probably not the worst the let them check it and make sure it's good.