This is a Win 94 barrel new old stock from Numrich [$15 + $5 shipping], screwed into a Mosin Nagant. The flat spots make it a nut.
.807" 20 TPI barrel adapts to .975" 16 TPI receiver and clocks the sight dovetail and headspaces without a reamer.
That was the first time, and maybe only time, I cut female threads on the lathe. But it was not the first time I did two equations and two unknowns [to get the clocking AND the headspace at the same time].