Correction: In the US, 15 minutes with hand tools and not paying the King's tax = a long time in jail.
I'm willing to bet that with round stock, a drill press, a pipe fitting, and a tap set, I could cut production time on one of these down to 5 min, beginning to end. Done by hand with no power tools, maybe an hour, or 20 min if you don't include the tome to cut the disc from the round stock.
I've said for YEARS that it's not the firearms that are the tough part. You cab build a gun (or at least something that the feds consider a gun, even if no self respecting gun guy would want one) in hours using standard machine shop tools and materials from a standard metal supply shop...or a hardware store, if you really don't care about safety. To top that off, read Oleg Volk's comments regarding manufacture of automatic weapons; they're easier to cobble together than semi-autos.
The problem is the cartridges. Manufacture of the cartridges is key.
Oh, and this suppressor? Pure awesome.