I checked with Huntertown, and they said it should be safe with a 10.5" barrel, but that they haven't tested it, and that it might not cycle. Has anyone tried it with a 10-12" barrel?

I don't see why not. Keep in mind I saw noticeable wear on the first baffle after only a couple mags on my Kestrel on a 10.5". I'd recommend the CF Gunworks QD kit and a YHM muzzle brake mount to prolong the life of the can on the short barrel.

That is helpful info. I guess I'll stick with 11.5" then. I think my best option by far is the Adams Arms Evo 11.5. I was only considering a 10.5 because a lot of cheaper uppers only come in 10.5, but once I add the AA conversion it would cost the same, and adding a monorail winds up costing even more.

Still, can anyone else report their experience use a Kestrel with an 11.5" (or similar)  barrel? Anyone using a Kestrel with an AA piston system of any barrel length?