Four Best in Class
I have four cartridges worth mentioning.
17 Mach 2.
It shoots at 2150 fps--nearly twice what a 22LR will do. Ammo is less than HALF the cost now of 17 HMR. Even very cheap 17 HM2 rifles will do MOA pretty easy at 100 yards. Yes the 17 HMR has more velocity, but in terms of Bang for the buck, the 17 Mach 2 is still the rimfire "star" in my book.
220 Russian.
With match bullets and Lapua Brass right out of the box, I've personally seen the 220 Russian WIN a 100/200 benchrest match straight up vs. the PPCs. It is very efficient, the brass is superb, and of course it can be necked-up and fire-formed into 6 PPC, the most accurate cartridge in history.
6mmBR
The 6BR or 6BR holds a ton of records from 300 yards out to 1000 yards. Ballistics, with a Berger 105, are very similar to a Rem 260 with a 120, with MUCH better brass and the .243/260 use 50% more power. It is easy to load for, perhaps the easiest cartridge to deliver 1/4 MOA you can find (after the 6PPC). As a varmint cartridge it's the equal of a 22-250, and gives up very little to a .243. 6BR--ask the man who shoots one.
7mm WSM/300 WSM
Now that Norma brass is available, the WSM cartridge family is really coming into its own. It is the "short fat" case equivalent for big bullets. Within a few years, I think the 7mm and 300 WSM will be the favored 1000-yard cartridge and it SHOULD be our military's sniper round. The ballistics of both WSMs are dramatically better than a .308 Win.
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With these four cartridges you pretty much have every BR competition and hunting need covered.