>>63903990
Yes. They require a certain distance from the muzzle to the cone to work effectively.

They recommend a crush washer and I would too, otherwise the proper torque will be marring your tenon unnecessarily. Washers have a very important purpose when it comes to distributing torque force and allowing metal on metal assemblies to not wear themselves to failure from vibrations, etc.

I used a single A2 flash hider crush washer. It is a bit taller than the distance they recommended but it just be within the tolerances because it does seem to be functioning as intended. Of course, I could be misinformed and I am getting more flash or concussion then I am supposed to, I also figure considering I've worn down the funnel mouth considerably, I doubt even if I had gotten the measurement distance exact it would have lasted long