Oh okay, so we're moving the goal post to try and make our point(as per usual)?
Fact is Larry, when comparing apples to apples, a saami Swift will kick the dog sh#t out of any 223 at the distances the OP is planning to shoot. Physics are physics. Twist em' both at 7 and run a 51 gr Hammer at 4000 out of a Swift and 3500 from a .223... nets 411,428 RPM's to the Swift vs 360,000 for the 223!!! Doh!! That ought to be worth a little extra goo for the Swift, don't ya think?? 300 yd velocity...2585 for the Swift, 2221 for the 223. +364 for the Swift!! Ewww...even more goo!! Heck, go back and run a good 50 gr cup n core, twist the Swift at 8, the 223 at 7, RPM's are equal but the 220 still still arrives much quicker to the 300 yd line. Even more splatter factor, I reckon!
More noise, more powder, more recoil...who GAF??!! Let the OP build what he wants. Maybe he wants a unique rifle/cartridge and not one like every other d-bag today sporting an AR/.223. The dude's got a stockpile of 220 Swift brass. Sounds like a good enough excuse to build one.
