Looking to build a SBR AR. Im thinking of going 10.5 inch upper but what if I want to change to a 7.5 inch later or something other than the original upper i have when i first register it? Do I have to re-register it or can i just swap them out?
You can just swap them out. If the change is a "permanent" one (i.e. you get rid of your 10.5" upper), you should notify ATF in writing but it still doesn't need to be re-registered.