Wayne.B wrote:
On Mon, 29 Dec 2014 17:27:49 -0500, wrote:

If you have the bull barrel model you can just make a hard plastic
rear bushing for your can and slide it on.
The stuff my buddy used was similar to StarBoard. It was a very snug
friction fit on the barrel and worked great on any Ruger MK without
modification. He did cut a notch in the bushing to clear the sight for
a better attachment
===

Some of the Mark III barrels have little detents near the muzzle end
which are there to provide a grip for set screws with "slip on"
devices like a muzzle brake, etc.

https://www.volquartsen.com/tags/6-barrel-add-ons
Compensators for MKII/III target guns? What purpose would that serve?
They have zero recoil and the action is all at the rear anyway.