Suppressors ? On Older YHM Hider/Suppressor Mount

[Wannashootit]

Customer sent me this (discontinued) suppressor mount from YHM (18 tooth) to install.
It's odd in that it has a non-threaded section with an ID of .782 behind the threaded section (5/8"-24t).

I called Yankee Hill, they asked for a model number but there isn't one engraved on it. They told me to email a pic, never heard back.

This design makes no sense to me, the back end is thin, doesn't look like it's meant to be the torque shoulder.
In the case of this customer's barrel (a fat shorty .300 Blk), I'd need to turn down the barrel OD behind the tenon shoulder to get this section to slip over the end of the barrel.

Anyone seen this before?

 

[roostercogburn98]

pretty sure that Is the mount for the AAC M4-2000 suppressor

 

[Wannashootit]

Could be, but I'm still trying to figure out "why" the large diameter, unthreaded section ahead of the threads.
What purpose could it serve? Haven't seen anything like this before on a suppressor mount.

 

[WhiteDingo]

It is for an AAC 18T can.

That portion in front of the threads is an index point for a bearing surface inside the can if I'm remembering right.

But you're correct, the mount is supposed to be socketed over the barrel shoulder so that the interior shoulder there bears. The AAC built flash hiders were the same way.

 

[Wannashootit]

Got it.
Thanks, guys.