they require high velocity 22 ammo, so forget anything match grade. thats the one advantage I have when my friend and I go to the range, he has a S&W 22a, and I manage to edge him every time with my KMK-678GC, and if we switch guns he usually beats me. he found out very quickly that the S&W jams on regular power ammo in a box of 300 he had a jam on at least 1 out of every 2 clips, when switched to high velocity it jammed only 3 times out of 250 rounds.