Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.
Does anyone know where to find a booster for a form 1 using a ‘c cell’ tube? Plenty that fit a D cell tube, but I’m trying to stay within a c-cell (1.25OD). Thanks in advance for any help.