Upper Receiver Lapping

[Sqr]

You sure about that?

It looks to me like it is functioning more like a locating collar that threads onto the receiver threads, then the barrel nut comes in after, torques on threads in the collar and jambs the shoulder of the barrel extension. Not an uncommon method of floating the barrel these days with many rail manufacturers.
But.
The barrel nut is the one highlighted:

D6950833-BAF5-428C-8E8B-F326418124F7_1_201_a by M J, on Flickr

Well If the small winged piece is only the barrel nut and the large cylinder spacer with the handguard mounting nut holes is separate I will be damned. Never had a piece like that and I have had a few Aero precision handguards.

 

[PinaKaleada]

You sure about that?

It looks to me like it is functioning more like a locating collar that threads onto the receiver threads, then the barrel nut comes in after, torques on threads in the collar and jambs the shoulder of the barrel extension. Not an uncommon method of floating the barrel these days with many rail manufacturers.
But.
The barrel nut is the one highlighted:

D6950833-BAF5-428C-8E8B-F326418124F7_1_201_a by M J, on Flickr

I’ve built mine with this exact barrel nut and it comes with shims just for timing.

 

[greentips]

Because this kind of barrel nut was first designed by Heckler and Koch for HK416 and then everyone in the US started copying it.

Now we see how proper engineering actually solves all the problems that demand patch work solutions like shimming and lapping.

PinaKaleada has explained it perfectly.

My MS did not require any reworking when using a very forgiving barrel nut.