I tried 250gr Sierra MatchKings and 250gr GameKings with R22, R25, H1000, and Retumbo. I couldn't get them to shoot acceptable groups (better then 1/2 inch-this rifle was built by Kirby after all) so I never ran them over a chrony. I shoot 300gr MK's over 90gr of H1000 for 2800+fps and couldn't be happier.