Long story short I got a MP5 pistol in a trade a few weeks back and want to have the barrel threaded, but I was told by a gunsmith he wouldn't do it and that once it was made into a rifle it is always a rifle. Anybody know the ruling on going pistol to rifle back to pistol? I was under the impression that it was GTG. I guess I could of left the pistol to rifle to pistol part out of the email but there is a hole drilled in one of the lugs where the fake can was attached. Also any one know where I can get the barrel threaded?

Are you sure it was originally a pistol? It sounds like it was a rifle with a fake can pinned to meet the barrel length requirement. Don't see why someone would pin a muzzle device to a barrel on a pistol. What kind of mp5 is it? Is it a GSG "mp5". If it was sold as a pistol from the factory and can become a rifle back to pistol if you wish. If it was sold as a rifle with stock and pinned muzzle device to meet the 16" barrel length, you can't make it a pistol.

Started as a pistol, I know the original owner. After I got my Bobcat clone rifle I wanted a pistol to run my suppressor since I decided against sending a form 1 for the rifle and we worked a trade. He bought it has a pistol and thought he would like it better as a rifle but changed his mind at some point, I definitely would not of made a deal if I thought this wasn't true.

If his gunsmithing is as bad as his knowledge of ATF regulations...........find another gunsmith.
ATF Ruling 2011-4