Draw lines (Witness marks)

[Jim Keenan]

We should also be careful about taking as gospel the theories of writers who know nothing about gun production or machine shop work.

Saxman, you are correct in that the assembler needed only to align the draw lines when installing the barrel. But that was done on the first, and only, installation of the barrel. That process, with its critical need for a proper crush fit, was not repeated.

And if each barrel was fitted to a receiver to be marked, how were spare barrels marked (and they are)? Even if each was fully installed, how would the anyone know that a barrel installed on one receiver would be OK in another receiver made at another time in another factory? Sorry, it won't wash.

The barrel shoulder and threads were fully machined, the draw line was marked using the gauge, and the rear of the barrel faced off. Then the sight base was machined and the extractor cut made by aligning on the draw line. The chamber was cut and the barrel was then complete, ready for installation. The proper "draw" insured correct headspace.

The entire process, albeit with another gun, is described, with pictures, in United States Rifles and Machineguns by Colvin and Viall. Every other factory did it the same way.

Jim