If you feel up to it, you could try to properly fit it by using a stone file. Or have a gun smith properly fit it.
I had to do that on a Czechpoint muzzle brake for my vz58. No matter how hard I torqued, it was just shy of indexing with the plunger. I used a fine quartz/stone file to shave off a tiny amount on the back of the brake and it finally "clicked' after torquing it on.
If you do it yourself, just be careful. It only takes a VERY small amount of material removal to make a LARGE impact during rotation.