I want to start into the SBR and Silencer game. I talked to my local shop and they have me confused big time. I wanna build the whole gun upper and lower, IS that Possible?? They say they need the serial #, well if I order the components to get the serial # for the SBR could I get in trouble?? Any help would be appreciated. I would like to start with the SBR because its not as $$$.