RE: what caliber?
Put another tick mark beside 22-250Rem. I was up in the air between a .223 and 22-250, and finally opted for the extra firepower of the bigger cartridge. The 22-250 shoots a bit flatter because of its significantly higher velocity, which also translates to longer range and more power when the bullet gets where it's going. Granted, factory ammo for the 22-250 is going to be a bit higher, but the difference is pretty small. Before I finally got my handloading setup completed I'd been shooting the Winchester USA 45gr JHP's, which cost me $16-17 per box of 40. I think that the 50rnd. box of USA .223 is about the same price. I mostly bought the stuff for the Winchester brass, but I found that it shot very well (.75MOA) for being on the cheap end of the price range. If you handload, the 22-250 will cost you only a few pennies more per shot than the .223 because of the extra 10 grains or so of powder the 22-250 burns. Small price to pay for an extra 300-500fps at the muzzle.
Mike