This is the barrel that the suppressor needs to mount to. I checked runout and had to clean up thread damage near the shoulder caused by crush washer. Note large radius at thread shoulder junction that will require larger chamfer on mating spacer.
I made a barrel fitting that would allow the suppressor to mount as far back as I can without hitting the gas block. The collar sets against the existing step that was already on the barrel between the thread shoulder and the gas block, not the gas block itself. Next I measured the distance from muzzle to the start of 20 degree taper on the collar. You can see it is approximately 0.100" too short of the preferred 2.050"/ 2.060" used for an M4 style suppressor(M4-S, M4-M, 14th model, 15th model, and 16th model). On 12th model suppressors the distance is 2.50".
Next I made a threaded adapter with 1/2-28 ID threads and 5/8-24 OD thread that will move the threaded shoulder forward about 0.100". I chamfered the entry hole for the 1/2-28 thread to 0.585" to clear the large corner radius from the barrel manufacturer.
Finally I made a .22 cal brake with 5/8-24 threads 0.63" long to fit the adapter. I made sure the adapter mates flush with the thread shoulder, and the brake mates flush with the thread shoulder of the adapter. 2.05" from front edge of the thread where the port starts to where the 20 degree taper starts on the collar will give approx 8 turns of thread engagement. To double check, thread on the suppressor and put a mark on it for reference and then unscrew counting the turns before it will pull off. I prefer 6-8 threads personally, but anything over 4 turns will be fine. Anything over 10 threads will start to have exposed brake threads inside the blast area and get carbon buildup making it hard to remove. The 12th model suppressors are 0.45" longer from the threads to the taper so when measured it should be approx 2.5" to get 8 turns of engagement.