You will need to start with a short action, .473" case head chambering, .22-250, .243, 7mm-08, or, .308. Then I'm guessing you will have to get a mag that fits a .223 Axis, since the SAAMI max OAL for both .223 and .450 bushy is 2.26". Then you might, *MIGHT* be able to bend the feed lips out on the top of the mag and then grind them down a little to make the opening wide enough to accomodate the .450 bushy. I have never done it or even seen it done but in theory it should work and the .223 mag will fit the stock of any other short action stock. It will be trial and error but I bet it would work.