Odd cuts in barrel extension. Not 6.5grendel

[woohoo]

One of the projects I'm working on is a leopard print AR for my daughter (don't judge:p)

Initially, as It's going to be primarily a plinker, I'm going 5.56. Maybe later when the mythical steel 6.5 shows up, I'll convert it.

Anyway, a guy offered me a barrel that has some unusual cuts in the extension that I've never seen. The upper I'm using is an A2 without M4 cuts.




Is this barrel GTG?

Thanks.

Some 7.62x39s are cut that way, some guys building wildcats like the 458 Socom also like the wide ramp.