i have a marlin model 60 that my father gave my son. we fired it quite a bit last year with no problems. i took it apart over the winter and refinished the stock and now 1 out of three or four rounds wont feed all of the way into the chamber. they will go in about half way, then you have to push the bolt the rest of the way closed to fire. i have taken it apart two more times and cleaned thoroughly but it still fails to feed. any ideas on things i may check for.