Re: 7.62 Suppressors on a 5.56 rifle???
I have been using my 7.62 SD AAC on my 308/6.5/6.8/ and three 223-5.56, and they work fine. All were threaded specifically for the appropriate QD attachment by a gunsmith. No problems, so far. While shooting I do check periodically to insure that the can has not vibrated loose. never had a problem there either.
I talked to Mike at AAC over a year ago about this and he said with the right adaptor and threaded properly should be no problem. Take your gear to a qualified smith and have them do the work. I also have my QD adaptors spot welded just as you would a short barrel on a NFA weapon. I have no intention of taking them off and this is just more assurance that it will not back off.
Make sure the QD adaptor is the right size for the projectile. A 223 adaptor will NOT work with a 6.8. Take my word for it. I put 30 cal adaptors on all my weapons, yep, ya gotta rethread the barrel. That is why I use a gunsmith with a lot of experience.