Quick answer is that there was a 1/2" x 3" (guessing) cylinder that screwed in under the front of the barrel, at least on the 7-3/8" barrel. The pistol came with a steel and an alloy cylinder (weight), the front end of the cylinder had a screw hole that was used to secure the false muzzle, or the muzzle brake.
I'm sure someone will be along with some pictures.