Infinitely more complex, expensive and inconveniente (as in less viable for quietly making guns when you're not supposed to be doing it because some soup letter faggot might go after your butthole) than either electrochemical machining or button riffling with a press.
dtic.mil
There you go, m8. There are videos about it too.
The only downside I can think about it is overall barrel durability (specially corrosion). Trying to coat that shit without shitting up your accuracy can be a challenge, but anything would be better than no rifling.
That's what you aim for when making the simplest improvised guns, shotgun have low pressure, you can use a common steel pipe with ease.
In Argentina inmates make that shit with gas pipes and nails. I'd use something a bit better if possible.
Sure, but guns would still be better as a defense weapon during the event of direct confrontation with the authorities (of course, while trying to ge the fuck out because you're not supposed to fight directly). On that situation, the risk of collateral damage (and even going full muslim) is very high with improvised explosives; you lack range and precision.
Some of that stamping is more difficult for small scale production than it seems. It would work if you capture a proper stamping machine. But that's a different story.
A zip gun can be made in half an hour.
Some shithole people from south east asia shit out guns in less than half a day of work. Button rifling can shit out barrels in a couple of hours once you have the process well established.
Electromechanical takes a bit more time.
Just handtools is a bit too much. At the very least you need a "big" hydraulic jack, a vertical drill that isn't shit and some hand tools. That is, if you want to make something that isn't utter shit.
If you're ok with shit, a vertical drill should be the bare minimum.
