Good to hear there is some consistency to manufacturers. I have one as well and I can tell you it is my favorite semi-auto .22 pistol. I think your 555 is def. an off box. I have the 333 boxes (same stuff different quantity) and they ran fine. In fact, the only ammo I had a problem with was winchester super X plastic sleeve ammo, which I thought would of done a great job in it. Bulk CCI mini mags (Choot'em stuff) had a couple of fail to fires, but fired on the second try. Good dents on the rims too. Have to be poorly packed primer for sure. CCI Tactical ran all day with no problems at all. almost 600 through it and it was smooth as butter. These are great pistols, easy to keep clean, easy to use. I was getting tight groups for a beginner too (3 inches with the odd flyer) at 25 yards.