BIG PITA. Pretty much need to have somebody with a lathe bore a .235" hole lengthwise thru a 3/8x24 bolt, 3/4" long. Get a $10 kit of Goop Plumber's epoxy. It can take 200+degrees F heat,and silencers DO get hot, in rapidfire. Spin the bolt in a drill, against a TRUED grindstone, and SLIGHTLY knock a bit of metal off of all 6pts of the hex head. It can then be driven into the end of the 8" long, 1/2" ID, schedule 40 PVC. the 6 pts of the bolthead will peel off a bit of pvc as they enter the pipe,centeringthe bolt.
The threaded end of the bolt is left protruding out of the "back end" of the pvc pipe. The female threads are tapped into a counterbore in the muzzle of the .22's barrel. After a couple of hours, when the epoxy is set, measure the thickness of such a bolt head with your caliper. Set your caliper and lock it, at half that value. Use the caliper's jaw to lightly "scribe" a line that distance from the back of the pvc tube (the bolt being flush withthe backof the pvc tube,ya see. Use a file to mark the center of each of 3 sides of the bolt head,on the outside of the PVC, skipping a side in between each mark. u pretty much need a little $50 drill press and a $10 drill press vise for the next step. without it, drilling the holes precisely and straight enough is very unlikely to happen.
At the intersection of the caliper scribe mark and the file marks,drill 3 holes, .200" deep. Wrap a bit of tape around the 1/16" drill bit, at .200" from its cutting lip, so you don't go too deep. If you drill thru the bolt head(into the .235" hole thru it lengthwise, where the bullet passesthru the bolt),you can have a noisy gas leak. If you do go too deep, some epoxy may save the day. get some .5" long, .085" roll pins. Taper-point one end,smash the rollpins joint shut with a vise. Counter bore the 3 pvc holes(but not the bolt head) .085". Hold the pvc in the vice, with the "piston" (from the baffle-forming kit) being inside the pvc, serving as a supportive "mandrel. Put a bit of the epoxy in each of the 3 holes in the endof the pvc. Using needlenosed pliers to hold the pin, start it into the hole in the pvc, and tap it home with a small hammer. Do all 3 pins, of course. Let the epoxy set up, presto, thread in one end of PVC. cut off the protruding ends of the 3 pins, using LOW rpms of the Dremel, and the cutoff disks. It's REAL easy to let the Dremel jerk these pins out of the bolt head, melt the epoxy, etc.
To check straightess, get a pcof window glass, $3 at hardware store. roll the pvc along the top of the glass, checking for bends,etc, before choosing that pc of pvc, after installing the bolt, do the same thing, looking for "wobbling" of the bolt end. Remove all "bumps" of displaced Pvc,epoxy, of course.
To get a "true" 90 degree end on the pvc,either spin it in a lathe, or very CAREFULLY cut it with a$10 pipe cutter, making sure that the initial marks around the pipe aling perfectly, before tightening the cutter, and going around the pvc again.
The bolt has to have an"empty thread" groove cut into it, near the bolt head,or it won't butt up against the gun's muzzle, 360 degrees,and be straight with the bore. You can cut this groove with a Dremel grinder and corborundom cuttoff disks. Use the same disk, and mandrel, but in a handheld power DRILL, to cut the internal groove at the front of the can, for the internal snapring. the Dremel has too fast rpm's, and will cut too deeply into the pvc,makingthe groove for the internal snapring. Then the brittle PVC will break at the front of your can, when you fire the gun.
A last rubber "wipe' and a washer sit atop the last screenwire "donut" baffle, and the snapring holds them in place. The washer should have about a 5/16" ID hole in it, however. The baffles have .235" holes in them, and there's a rubber wipe in between each of the .5" (approx) long baffles. Heat the rounded end of a foot long,.235" OD drill rod red hot, and use it to "cauterize" holes in the rubber disks (scissor cut out of truck inner tube "rubber".
Test fire first few rds down into a 2x4 board on the floor of your shop. (concrete floor, or use TWO such boards) after each shot, check the condition of the washer and snapring. Observe each hole in the board. Is it nice and round, or oblong? If oblong, the bullet's tumbling, from hitting a baffle.
Wrap both ends of the pvc with fiberglass thread-reinforced packing tape. No, NOT lameassed duct tape, either. Pvc is easily cracked, and the ends of the can are highly stressed. You can, of course, quickly DESTROY such a silencer, stomping on it. that COULD be important,you know.