I'm building a new rifle off an old Remington 721 action. The rifle will primarily be used for coyote, hogs, and deer (in that order) and enough power to take a mule deer if the opprotunity was ever available. I do want to stick with a long action round and something without a lot of recoil. Most shooting will be inside 200yds but I want enough killing power to go out to 500yds. I have a couple calliber options in mind but I'd like everyones opinions on what they'd use. It doesn't have to be a commercial cartridge but I want something I can easily get brass for. It will not be a long barreled rifle, 20-24" (the shorter the better). Any help will be greatly appreciated.