RWS SS HP has shot very well in both a CZ 453 and my current Ruger 77/22 RSI. Aguila Match about equals it, but no HP, of course.
Neither is cheap, though, especially the RWS. Standard velocity ammo doesn't shoot as flat as HS, but wind-drifts less.
.22s can be very finicky, and you really need to test candidates in your rifle. Most shooters seem to think that you have to shoot 10 rounds or so with each ammo type to "season" the bore with the different lube before test results will be accurate.
The other method is to buy a bunch of holler points and have at it. If I ever go p-dogging, I'll buy a Hummer.
