Every rifle is different, every brand and type of ammo varies from lot to lot. For those of us stupid enough to shoot rimfire benchrest, it's a game that's heavily dependent on finding the very best ammo for your rifle. Just when you think you've found the magic ammo, you run out and the next batch doesn't shoot worth a darn in your rifle.
For the average joe, shooting a semi-auto, it's hard to beat CCI SV for 5-shot groups around 5/8" at 50 yards, with a few flyers in opening groups to about an inch.
For very accurate sporter bolt actions or highly-accurized 10-22s, it's hard to beat the most expensive and second most expensive of Lapua, Eley, and RWS, but testing to find the right batch is still necessary. Less expensive types include Wolf Match Extra and SK match ammo. It's possible to find the less expensive ammo shoots very well in your rifle. If so, buy as much of that batch you can afford (or find).
There's no guarantee that the most expensive ammo of one brand will outshoot the next grade down. If you want to get the very tiniest groups, you've got to have the best rifle and ammo...test, test, and test more!
The best part of all this testing is that you can also work on holding techniques, equipment improvement and ability to read both wind flags and mirage, etc.
