I was wondering if anyone makes an adapter that will allow an DIY can to interface with a Surefire or Knights QR flash hider? I only have two ARs, one has a SF hider the other a KAC hider. It doesn't matter much to me which rifle I use the can on, i'd just rather not unscrew the hider and screw the can can on every time I want to shoot suppressed.

Also is possession of a quick release adapter, if they are available an NFA violation? (my Form 1 is still at the ATF)

QD mounts are not silencers, or silencer components, so they are legal to own and/or use with or without approved silencers in your possession.