Unfortunately the Limit doesn't have the luxury of the slots found on the Super Briton (neither does the Gat or later Briton) so you have to find some other way of stopping the barrel rotating when you try to unscrew the muzzle nut. I have found the best way is to make a thin metal plate with a U-slot filed into it which can be worked in between the spring guide and the knurled muzzle nut and then pushed around the barrel. Tie some cord around the ends of the plate ( best to drill two holes in ends of the plate for this) to make a loop so that when you push the spring guide back and compress the spring you can hook the cord around the breech to hold the sprng guide back and expose about half an inch of the barrel. You can then grip the exposed barrel with pliers while you unscrew the muzzle nut. (The barrel might be burred over the nut so remove the bur with a file before you start). Just reverse the procedure to reassemble.