No that is not with powered equipment, but only with sine-bar or helical post machines. All hand pulled. As I said, that what I was told. I have never seen one done that fast, but that doesn't mean it can't be done. It just means I can't do it. Keep in mind I am talking about the cutting only, not the reaming, lapping, crowning, contouring and threading.
I have made probably 125 barrels in my life. Not a large number in comparison to the men who do it full time. But enough to know how and I I got quite good at it.
I was proud of the accuracy I got from my barrels.
I never did any from welded scarfs like Wallace Gusler did. All mine were deep-hole drilled on a lathe. I had only a short stroke with my drilling set-up, so I would have to drill about 1/2" at a time and then clear the chips. I would start with 1-1/4 to 1-1/2 steel and a 3/8 bit most times. I could get a pretty straight hole, but NEVER a concentric hole.
So after the pilot hole was drilled I wold set the bar up on centers and true it up so the bore would then be concentric with the outside of the bar. When that was done the bar was slimmer, often done to about 1" or in a few cases even a bit less. Then I ream to bore size and lap it to 220 grit. I make a rifling head with a hook cutter and a screw jack and I cut the grooves about .0001 at a time. So cutting a scratch 1/2 thousandth deep, you can see it would take me between 16 and 24 passes per groove, and then I had to advance the bar 5 more times for a 6 groove barrel, or 6 more times for a 7 groove barrel. Add to that the time to set up the cutter for every pass and the time to sharpen the cutter which was pretty common on most barrels.
When all the cutting is done I would lead lap the bore full length down to 1200 grit. When it's bright and shiny I would cut off the muzzle end about 3" and crown it. I would thread the breach and install a bolt to hold in a 3 jaw chuck, install the barrel back on my lathe and cut the swamped shape into the barrel. Now I have a swamped round barrel.
Lastly I set the barrel on a flat steel table and file a flat on top of it. I use simple shim stock to support the waist of the barrel so it doesn't flex away from my files. Then turn the barrel so the flat is down on the steel table top, and do it again. Now I turn the barrel 90 degrees and using a square, I gauge off the 2 flats, to make them come up at the 3:00 and 9:00 positions, and file another flat on top. Turn 180 degrees again and you now have 4 flats at the 12:00, 6:00, 3:00 and 9:00.
At that point you simply file off the round parts and connect the flats you have made with the last 4 flats you are about to make. The 1:30 flat, the 4:30 flat, 7:30 flat and 18:30 flat. Now dress all 8 the flats down to a smooth file finish.
When that is done I make and install my breach plug, and it's ready for a rifle.