Pictures really help me out figuring out what needs to be done, but these muzzle brakes are really no big deal. If you know for a fact that it is only silver soldered, then you simply heat up the brake and occasionally test the brake to see if it will spin off and spin it off when the solder releases. If pinned, you grind/dremel the brake until you find the pin/setscrew then you work to remove it and spin the muzzle brake off.
No drilling of the muzzle brake or cutting of the barrel is necessary. If you were willing to do either of those, why not just work to remove the brake and save yourself having muzzle work to do after you are done.
IF your muzzle brake was a slide on & pin model then you will obviously have muzzle work to do after the brake is off.
AND ALWAYS REMEMBER....................if you remove ANY LENGTH, that is any length off of a 16" barrel to cut off your muzzle brake, whatever you install on that barrel will have to be PERMANENTLY INSTALLED and total barrel length has to be over 16", or else you may risk owning an unregistered short barreled rifle.