not sure, I used good bases and rings but I think the slam of the bolt going back and forth.. especially the forward motion of the bolt ####ed them....
both cases it was crosshairs going SPROING..... buthe replaced them lickity split and I sold the new ones on the board and went and bought a luepold rifleman for $250.
frankly the best deal going for a scope is the luepold rifleman line....
as an aside the only other scope brands I have had problem with was a simmons scope on my mini14 back in the early 90's that went tits up (adjustments would not hold and every shot looked like we where playing bingo) and the other one was a bushnell rimfire model, one half of one crosshair came loose.
you pay for what you get,,,.... why buy twice when for a little more you can get something decent.