Originally Posted by
Wormydog1724
It's my understanding that AAC used to make their flash hiders this way. The threads were further inside the mount, with the wrench flats further down and slipped over the barrel somewhat. In essence creating a hollow, thin, WEAK point where the most stress would be applied when attaching and removing the mount. They have since changed the design so the threads are actually under the wrench flats creating a solid, thicker, STRONGER contact point for the wrench.
On a side note, is that a crush washer behind that mount? If so, that's definitely not factory installed. Even shims aren't necessary for that type of mount as no indexing is required. Hmmmmmmm.