I'm wanting a Rock River Varmint in .223 in either a 20" or 24" bull barrel. Talk to me about this rifle/cartridge combo as it relates to longer range shooting. What's this cartridge like at long distances, 300-600 yds.? This rifle would be used strictly for paper punching or possibly a praire dog hunt. How's the .223 perform at long range, and what bullets would you recommend for accurate distance shooting? Loads? Scopes? Thanks.