Lapua CenterX and Pistol King are two good ones to try, along with RWS-50, and perhaps a couple other RWS products, Rimfire ammo is so specific to the rifle that it's really hard to just pick some.
I know a guy who won the Rimfire Nationals one year, and has since given it up because of the ammo "chase" trying to get good lots of the stuff, and hoping that expensive stuff will shoot. Lord only knows how much ammo is stashed in his basement even now, as this lot or that lot didn't measure up.
He finally just quit and went to exclusively centerfire, as he could at least control the ammo aspect of it.
I know Lapua Pistol King ammo is REALLY good in my CZ 452, but at $12/box, I'm not going to bother. And Pistol King is relatively "cheap" compared to Midas or some of the others.
