Just bought a 22 mag. barrel for my T/C Contender 10" (old style) pistol without a forearm. I have a 218 Bee 10" barrel with a forearm but the screw doesn't match up with the new barrel. The 218 Bee is a octagon barrel and the new one is round and seems to be heavier than the 218 Bee. What should I look for in trying to buy a forearm for the new barrel.