Yes, it will fit. The 7.62 and 5.56 blackout mounts have the same outer dimensions. Be sure to buy the 1/2-28 threaded mount for .223/5.56. I swap between my M4-2000 and 762SDN-6 all the time on my 5.56 rifles.
The mount will barely go past the threaded portion of the barrel. By barely I'm talking 1/32" to maybe 1/16". The suppressor does not reach the back of the mouth when attached. You should have no issue with clearance but it will be close...the suppressor when mounted will reach as far back as where your crush washer sits now.