Look for the blemish at the bottom of the brake, then very carefully take a dremil tool and remove material there until you can see the pin, then take a small drill bit and drill into the pin enough so that you can either remove the pin or unthread the flash hider. That's the way that I've done them in the past, there may be a better way of doing them that Dad or Gary use.
*NOTE* This should only be attempted by someone with proper equipment and preferably some machining experience to prevent scrapping the barrel. DSC/J&T Distributing is not responsible for any damage as a result of attempting to remove the brake. Legal disclaimer Done!