I built mine and it didn't turn out too bad. Paint should make it look better.
How I did it -
- Started out with 1 1/8" steel rod.
- Drill out center to 13/16"
- Thread to M22x0.75 (nice to have a lathe!)
- Measure outside diameter
- Compute distance for notches
- Cut notches with dovetail
- Finish notches with 3/16" end mill
- Cut parallel wrench slots
- Clean up with wire wheel
I'm not entirely satisfied with the vents. The mill walked on a few of them and I think it was due to my dull cutter. I had to finish off the errors with a dremel cutter, so it isn't as PRETTY as I'd like it to be. I'm sure it will work fine. Its length adds 1.75" past the muzzle.
I also found that my 60 degree dovetail cuts just deep enough that I could not cut all the way through without enlarging the hole too much. In fact the first two grooves are a bit larger than the others, but I doubt you would notice unless you gave it a really close inspection! I wanted the edge to be beveled, so that is why I chose the dovetail. I could have done it with a ball end mill directly into the groove, but I don't have any ball end mills to play with... yes let the jokes fly!
I ran into a problem when cutting the notches. I wanted to go smaller but the smallest I had was 3/16" and it was dull. I've tweaked most of the play out of my mill so it is very difficult to turn the dials, but it shouldn't walk any more like that. I may open up the slots to make them more straight. We'll see.
Has anyone used these and can say for certain if they work? I'm real interested to get a feel for it with- and without the brake so I can say with certainty that they actually do something.