If you call Choate machine and tool they will sell them to you
Cost like $1.50 each
They send you a package with two in it. One fine thread one coarse.
By the way I took it out yesterday and shot it about 10 times
I shot 7 1/2 birdshot, 00 buck and 1 ounce slugs all 2 3/4" long
10 yards everything worked great except the recoil is tough.
20 yards the birdshot was thin I didnt try buck
20 yards the slug was real good at fifty not bad
This is definately a close range firearm.
If you carry it a lot and shoot it a little it works great.
Kid