Shaggy

Midwayusa has a AAC 300blk pistol upper. Advanced Armament Co (AAC) AR-15 Pistol A3 Flat-Top Upper Assembly 300 AAC Blackout (7.62x35mm) 1 in 8" Twist 9" Barrel with KAC URX III Modular Free Float Quad Rail Handguard, Blackout Flash Hider. Its on backorder but it is out there. Hope this is what you are looking for. If you get one I'd love to shoot it. Im considering going the 300 blk route as well.

I think a 45 can would be to large a hole to have any real db reduction for a 22. I have shot the 45 AAC Tirant on a Sig P220 and it was very quiet. Maby start with a good 22 can and then when the bug bites get a few more.

Alwaysonjohn, one can that I have been looking at is the Liberty Mystic. Its a 9mm can but is rated for all kinds of stuff from 17hmr to 300blk. It is a monocore and can be cleaned easily. Might consider this so you get a lot more use out of your tax stamp and wait time then a purely 22 cal can. Hope this helps, Shaggy

Sorry, I did not see the post about the Sig 522. Another option is to get the Tatical Solutions upper for your M4. It is pre threaded and then you do not need to spend the extra $200 for the stamp and wait 6 months. Get the Element and enjoy. BTW, have you looked at the SWR spectre II, or Liberty 22 cans? I hear great things about them both. Just trying to help. Whatever you get make sure you can take it apart for cleaning.

I believe that Gemtech had done a few already sbr'd and suppressed. I saw them on Genbroker.