I've looked at it to try in an AR as well. I believe it's too short to run reliably without some spendy custom work. I haven't had a dummy round or two to play with, but from what I can tell, it could be tricky. If you do want about the most amazing reloading and in-depth cartridge info book ever, order a copy of the Garin family cartridge manual. Lots and lots of hours into making that one. Absolutely amazing. The Garin in pretty close to the SMc, but not quite as hot.
.20 Tactical/Practical are proven winners. If you're looking at performance, you might check out more of the .20 wildcats based on .220 Russian brass. .20 Beggs, BR, PPC, Dasher. These may not be long enough to feed reliably either, but you would have to talk to some builders. I can get the .20 Beggs to feed great with dummy rounds, but don't have a rifle for one yet. Robert Whitley didn't think the Beggs or .20 Grendel would feed well. He thought that the bullet was too short and by the time the bullet was hitting the feedramps that the case would come out of the magazine feedlips causing possible failure. They can all be done, it's just how easy and how expensive. Tony Rumore from Tromix used to do AR's and Mini 14's in .17 MIV without too much modification.