$30 UMP/USC trigger? Where please?The ATF Tax Stamp on the SBR would be $200. Compare that to the cost of compliance parts and you're coming out ahead by going the compliance route. The only redundant parts on my UMP that I had to buy for compliance was the trigger ($30) and the mag baseplates (3x$9). If you aren't going to actually replace the barrel, it's not worth the extra cost and hassle to go the SBR route IMO.