A while back I set up a trust and submitted a Form 1 to the ATF to build a silencer. It took a little over two months to be approved, but eventually I received my tax stamp!
I don't really know much about silencer design, but this is what I came up with after reading through a lot of forum posts about what's supposed to work well. There are seven K baffles, each 1" OD. There's also a .4" long blast chamber at the front. The first baffle will be steel and the rest are aluminum.
First I drilled the 17/64 (.265") clearance hole for the bullet. From what I've read it's not super critical to have a really tight clearance hole.
Then I came in with a little boring bar and bored out the inside of the cone to a 60º included angle.
Next I used a parting tool to come down to the baffle's neck diameter.
Then I turned the outside part of the cone. The wall thickness of the cone is .070". Maybe a little thick, but that's better than too thin.
Next I parted it off.
Then I flipped it around and used a HSS form tool I ground to make the concave face of the baffle. I believe this dish shape is to get the gas to flow turbulently.
Then I took the baffles over to my milling machine to mill the hole in the side with a 1/4" ball endmill. This hole allows gas to escape into the donut shaped chamber formed by the baffle and the ID of the silencer tube. I also put a divot on the concave side to increase the turbulence.
Here's all seven baffles. The first one is steel to take the brunt of the blast.
Next I made the silencer tube end caps. These have 40TPI threads around the outside. This one is threaded on the inside to attach to the gun, the other has a 17/64" hole through it.
Next I reamed out a piece of aluminum tubing to 1.005" ID and threaded the ends until the end caps threaded on easily.
I milled two flats on the end caps so I can take them off with a wrench.
Next I stamped all the necessary stuff on the tube. I stuck a long piece of 1" OD steel inside to prevent putting a kink in the tubing. Hand stamping is seriously nerve wracking! I was freaking out a bit thinking I was holding the N stamp upside down and felt like an idiot when I realized it didn't matter.
Finished! One completely legal homemade silencer! Now what to do with it? All of my guns are old and too sentimental to thread.
Aha! There is one gun I have that I don't mind working on! I took the barrel off and threaded the last 1/2". My lathe is a 13x40 and I don't often get down to this end of the bed.
A silenced Assault 2x4! Here's how it sounds. The first shot is unsilenced, the second silenced. I don't think the microphone on my phone does the sound any justice, but it's the best I can do.
My silencer works pretty good! I've never heard a silencer in real life, but the click of the bolt hitting the cartridge is about as loud as the crack on this one with subsonic ammunition. I felt like James Bond on the first shot haha.
Here's a target showing my amazing shooting skills. I threw out the worst shot of each 10 shot group. The silencer raises the point of impact about an inch.
Shooting this gun is tough. The trigger pull is only about 6 pounds, but it's about 1.5" long and gritty. You can hear the trigger spring clicking as you're squeezing the trigger and you can see the bolt shifting around in the rails in your peripheral vision. Plus the whole gun jerks backwards when the bolt starts going forwards. Good old Newton and all that...
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