i have a bushmaster AR15. and, i was thinking about getting a different upper that was chambered for a cartridge that would be feasible do use on deer. i would like to use it as a moderate range rainy day gunbecause of the matte finish and the chrome lined chambers and barrels. or, a stainless steel barrel. i know that there are other AR style (AR10) rifles chambered for the .308win. but, i would hope that i could find an upper for my AR cheaper than buying an entirely new rifle. of course, the .308win probably out performs any cartridge that can be chambered in astandard AR platform. again, i'm not looking for any long range performance anyway.

what chamberings would you recommend? what uppers? where to buy? have you heard of any issues from using different uppers on a standard AR15 lower? will they hold up to a cartridge such as the 450 bushmaster?

how well does the 450 bushmaster perform in a real world situation? i was on hornady's website comparing this cartridge to the 444 marlin. which i have with a 18.5" barrel. "according" to "their" ballistics the 450 bushmaster out performs the 444 marlin, slightly. plus, i checked some websites and the 450 ammo is an average of $6 a box cheaper than the 444 marlin. performance wise i may not gain much, but i would like to try something different. suggestions anyone?