Are we not talking about this yet?
www.hornady.com
Yes, I'm aware of the 22 Grendel wildcat that's been around forever and is probably the ballistic twin of this. I almost bought a 22G but the stories of having to neck turn scared me off, plus lack of barrel maker options. A factory brass equivalent of it has me interested again.
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22 ARC - Hornady Manufacturing, Inc
The 22 ARC brings you the exceptional power and performance of the 22-250 cartridge, all elegantly packed into the compact and versatile AR-15 platform.