Mounted my new Burris MTAC from Cabelas deal on my M77 .308 AK today. The clearance between the front bell and rear sight is at least .045 inch/ 1.13 or so mm. I know the scope will flex with recoil and normally if mounted over the barrel, it will need some gap. Is this enough gap since its over the receiver instead of the barrel? The receiver doesn't flex like a barrel does.

It might hit, hard to say.  Variables such as the rigidity of the scope, rigidity of the mount, and rifle itself all come into play.  The amount of flex in a given mounting system is a guessing game until you actually fire the rifle to know for sure.





If it does hit, it's equally hard to tell how hard it will hit.





The pic below is of an older set-up on a .308 Vepr of mine.  There is 1/16" clearance between the scope objective and the RSB.  The scope would hit the RSB when firing the rifle, but never hard enough to cause a problem or do damage to the scope.  It wore a little finish away on the scope where it was making contact with the RSB, but that was it.  





Not ideal by any means, but it caused no problems and the scope is still going strong today.  I could have gone with higher rings, but I decided to let the situation play itself out.







 

Took it to the range today, it did ding the scope slightly. I'm going to mill down the rear sight a few thousands and test it again. Will update in a week. Other than that it shot well and is a good conversation starter.