Reducing number of No.4 Barrel grooves to speed production?

[Bruce_in_Oz]

Useful article here:

Firearms History, Technology Development: Rifling: Manufacturing: Broach Rifling

Broaching requires a serious upgrade in machinery from the basic “single-tooth” cutter method.

Once up and running, the production rate is quite high; the complex tool travels through the bore ONCE and the rifling is finished.

The other contender is cold (hammer) forging, as developed by out Teutonic cousins. They had to come up with a production technique that could keep up with their consumption of machine-gun barrels. When you have a fleet of thousands of MG-34 and MG-42 (and several other) guns at “work”, the demand for replacement barrels is ferocious.

The only fly in that ointment is the supply of suitable materials and machinery to make the mandrels and the rotary-hammer machines themselves.

The US used broach-cutting for some production; one notable product was all of the National Match M-14 barrels.

They also used a LOT of “traditional” machines.

Meanwhile, also in the US, another method arose: “buttoning”. The idea dates back to the late 19th century. However, it languished until the engineers at Remington refined it in the early 1940s