Rifling a Gun Barrel
This from The Truth About Guns:
[H]ere is computer animation of a “cut” rifling machine, showing all the parts and how it works. “Cut” rifling does the lands and grooves one pass at a time as opposed to “broach” rifling that cuts all of them at the same time. Then there’s “button” rifling which simply presses the rifling into the barrel. Another option is “hammer forging” where the barrel is placed over a mandrel with the negative image of the lands and grooves and then pounded to fit the mandrel, transferring the image to the inside of the barrel.