Sterling Optic Mounts
JPoint or Docter Optic Mount
(Tactical Firearms Academy was the originator of this mount for the Sterling)
The mount has two pins that extend into the optic itself. These pins were CNC'ed from the optic base material. This allows you to remove the optic and re install without having to re sight the gun. You can remove the optic and still use the peep sights, the mount doesn't interfere. I have three mounting holes in the base, but you will need to position the mount and choose one to use.
Give me your SMG's tube diameter (if not a Sterling) and I can make a mount.