Barrel nut design on Mega MTS and Vltor VIS

[Stubb]

The MTS and VIS use very different barrel nut designs. The MTS nut is threaded on the outside and pushes the barrel extension back against the receiver. The VIS nut is threaded on the inside and not only pushes the barrel extension back against the receiver, but it also surrounds the barrel extension.

Aluminum has twice the coefficient of thermal expansion as steel. It seems like the MTS design might loosen up as the rifle got hot even with the barrel nut tightly torqued, as the receiver would pull away from the barrel extension. But I'm wondering if this is purely a theoretical problem given the temperatures and tolerances involved.

—Andreas

[HS2]

I have a Mega monolithic and have put about 3k rounds through it. I haven't experience any problems with loosening.

It's easy to assemble and very solid.