I have seen all sorts of stuff used, especially a few years back before rules were altered administratively by the ATF.
We have made some basic turned aluminum rod designs, about 6 chambers turned, inserted into a 1 inch tube, screwed together with a perforated nipple as the blast area. Work pretty fair for 22s, especially on longer barrels (over 5 inches). Simple lathe work and a drill press.
Looking at more exotic K, M, etc baffles and seeing all of the machining steps involved. I suspect a lot is diminishing return on the labor involved. Didn't know if some code was floating around on some of the steps.
We would love to stamp everything, but we need to research various shapes and angles, etc before investing in a tool set.
Fun stuff, though.