If you have to defend yourself while leaving the bank or walking down the street at night, whipping out a HK 45 with a 8" silencer is going to look a little bit "odd" in the court room, or a 12" shotgun for that matter. On the other hand in your house is a different story..
Look at your NFA paperwork and see what your reason was for purchasing a Class 3 Weapon..... Bet is says "COLLECTING" not "SELF DEFENSE". That being said i do have a 6.8SPC LWRC PSD M16 witha 8" barrel to defend my home and of course it has a Gemtech Can on it.
D