Hi, I have a Brocock and thought that the adaptor looked quite small and weak. I found that the silencer kept comming loose, I was afraid to lean on it too much and strip or bust the adaptor thread. My answer was to make a sleeve that went down the barrel to just short of the barrel band, this was a close fit to the barrel. It then stepped down internally to the 10mm size of the thread and tapped to fit (10mm X 1mm.).
It then extended falword and then was tapped to fit a standard silencer. (1/2" X 20 tpi.). If I remember correctly it was bored to 6.5mm.
It has never moved since. Hard to describe, much easier to do.
I hope that it helps.
Cheers.
Geoff.