This is interesting: Educational Zone #130 - Does Cleaning a .22 Rimfire Rifle Barrel Hurt Accuracy? - Page 1 I felt an experiment was in order. I have a new Ruger MkIII with 5" bull barrel. From all accounts I've read on the web, Ruger MkNs are a nightmare to clean. I guess "nightmare" is a relative term. Was it more difficult than say, a Beretta 92F? Yes. But, I wouldn't say it required an engineering degree. Just so I would commit it to memory, I assembled/disassembled the pistol about 15 times. It was tougher in the beginning I guess because the springs were tighter here and there. So, initially, I had to apply some elbow grease and one or two times, I thought to myself "Oh, I hope I haven't gotten the rear sight out of zero." The first time I shot the pistol at the range, it was very accurate. I was impressed. So, tonight, back at the range: I don't think cleaning the barrel affected the accuracy at all. However, cleaning it may have moved the zero. I was dead center accurate again, but this time, the variation of shots was not all over the bulls-eye--that is, random. All of my shots were a half-moon on the bulls to the left. No shots were from noon to 6pm. Odd...I didn't notice this on my first shooting. It was as if I had drawn a line with my shots. Perhaps I was pulling slightly. This has picqued my curiosity, so, now I'm going to have to figure it out. But, I don't think it had to do with the barrel cleaning.