I would think that a ball .003 over size would screw a quality air rifle up, blown seals, leaded bore and maybe worse. I have an 70's era 225 Anshultz(sp). Pellets aren't that pricey so pick up a 1000 mixed types and see what shoots best. I told my sons, that if I caught them shooting BB's out of the pellet rifle, I'd spank (read that BEAT) their butts until I couldn't sit down. I came home from work one day and my oldest son and his best friend were shooting the pellet gun in the back yard. They were shooting clay pidgins, prone. I laid down with them and took a turn... hit dead center then put 6 more in the same hole- I'm pleased with myself. they start laughing saying the objective is to break the clays and I failed. So I shot one shot a the last 6 clays we had and broke them each with that one shot, and told the it was foolish to poke an old bear. Ivan