Simon, I can only echo what the other guys have said, very impressive handling of the Dremel, the MB looks like a shining jewel.
Maybe too late but here´s a photo that might be useful;
As you can see, inside the first chamber, there are two rings with six cut outs (for some sort of a spanner) on this "lighter" muzzle brake.
Also at the back (on the extreme left in the photo), on the locking ring, the cut outs (four of them, also for some sort of a spanner) they only go a certain distance not the whole width of the locking ring.
At the front, two cut outs (diagonally) to help screw the MB onto the barrel.
There are also a French drawing that show some of these details but be aware as it contains some errors, se here;
http://www.panzerbasics.com/index_files ... awings.htm
Cheers Per