I kind of gather old barrels from anybody that doesn't want hem or want too much for them. In the junk pile, I found and old rusty, nasty 20 gauge 3" 88 Topper barrel. Checked it on my 500 Magnum Handi frame and it locked up well. I have been kicking around the idea of a suppressed shotgun for several weeks. I hit a good stopping place with my other suppressor work and went for it.
While I could just hang a big can on the end of a barrel, that would make a pretty long barrel, heavy and awkward with all that weight at the end. Also since pretty much all 20 gauge factory ammo is supersonic, the amount of suppression would be limited more than I wanted. So I decided to make a more or less integral suppressor. It is in fact integral and permanently attached to the barrel. It only adds about five inches to the barrel, but the OD of the can is 1.75 inches. It LOOKS like a big suppressor from just in front of the foreend to out there to the next county.
But it WORKS! It ain't slick like the big guys make cans, but I am pleased with it as a prototype. First two loads were Number 3 buckshot. -- wanted to see if it would hold together. Then I shot a bunch of field loads. To myself and two other observers, it sounded like a 16.5 inch .22 with something like CCI mini-mags. Subjectively, behind the gun, it seemed much quieter.
I started out by drilling umpteen holes on 0.5 inch centers along the top and the bottom of the barrel. To keep the rear (brass) bushing from moving back on the barrel, I brazed a ring larger than the ID of the bushing all the way around the barrel. Then I reamed out the inside of 7 fairly heavy 1.5 inch fender washers to just fit over the barrel. Each of these was welded two places on either side to the barrel.
The bushing (brass again) that fits over the muzzle end of the barrel gave me a bit of a quandary. Tried threading 3/4 x 10, but the barrel was to thin, as I quickly discovered. On a rifle barrel suppressor built the same way I can use schedule 8 set screws turned into indentations drilled in the barrel. Again, not much steel to work with. I finally decided to notch the bushing where it met the barrel and put w bead of weld in two places on either side, making sure the notches were filled so the bushing could not turn on the barrel.
The outer tube is a piece of seamless double-walled aluminum with total wall thickness of .125 inch. The end cap is a brass bushing that makes the far end of a small expansion chamber. There is room there for about three baffles between the muzzle and the end cap, but I don't think I need them.
After test firing, I decided I could drill a few more holes in the barrel. Hopefully that will make it quieter without adding weight. If I can bleed off enough gas to drop the velocity subsonic, it will definitely get quieter.
I am getting spoiled to suppressors, Besides reducing recoil -- with or without dropping velocity, it is nice to get the whump from a gun without all the bang.
(Type 7 FFL and SOT, we are legal and so are the suppressors)
