Pastor, research the Olympic Arms UMAR. You need this rifle to accomplish your goal.
We, here, know nothing about that rifle, and none of us here have that. Don't ask us questions about it - it will do you zero good, in search of information on it. I'm just sayin'...
Now, with that information, the UMAR was designed to be able to shoot the 22-250. The rifle itself is between the AR15 and 308AR - they made it that way, to shoot the 22-250.
Sounds like that's what you need for your wildass wildcat round. Keep in mind, you CAN NOT ORDER A RIFLE FROM OLYMPIC ARMS. You don't live in Washington State, so they won't sell to you. Your only choice is to order it, or get it, from an Oly Dealer.
Now, once you get this rifle, and it's mags, you can begin the heinous quest of finding a reputable AR Gunsmith that will custom-chamber a barrel for you, maybe machine a new bolt for you if that's necessary, etc.
Good luck. Here's the link - surf away:
http://www.olyarms.com/shop/umar.html