Machined a suppressor adapter for my brand new HK VP9 from a piece of free-machining steel I salvaged a couple years ago. Was originally an axle in an old discarded treadmill. M11x1 CCW to M14x1 CCW. Surface treated with Caswell black oxide gel and sealer. Hot oxide treatment would be more durable but this mostly just for shits and giggles, I don’t actually plan to run the pistol with the suppressor ‘cause the extra weight makes the barrel sag and the slide drags along the underside. Also, the damn thing flash-rusted on me in the 14mm threads after washing the cutting oil off while I was checking the fit and then got distracted! :P