RE: Help with new caliber
500 yds for what? paper, varmints? Other than that, there really isn't a need to shoot 500 yds. The 270 would surely take a deer at 500 yds but like James said, you already have a 7mm mag. The .243 would dipatch coyotes and smaller out to 500 yds but you would really be stretching the 223. And to consistantly hit anything at 500 yds, you would have to start with an accurate rifle. A rifle that can only shoot a 2" group at 100 yds is going to shoot 10" groups at 500. And that isn't accounting for wind drift which could be substantial at that yardage.