Here are a pair of Ruger .22 Autos, a stainless MkII and a blued MkIII, both of which were 5&1/2″ bull barrels. I cut both barrels to 4″ and then threaded them with the standard .22 rimfire thread shank of .500″-28tpi”x.400″. The first pictures show the muzzle threads and the thread protectors made from the cut off muzzles of the barrels.
Here they are with a pair of suppressors attached. The large suppressor on the stainless gun is a Thompson Machine Isis-2 9mm with a fixed barrel mount. The small suppressor on the blued gun is a Gemtech Outback IID. Until the last few years you would not want to use a center fire suppressor on a .22LR host because of how filthy the cartridge is. Today many of the newest suppressor designs are user serviceable. The Isis-2 pictured is one of those new designs.