You could probably send your barrel to Bob Hoyt in Fairfield PA and he can make one for you. Getting a Breech off a Renegade as said earlier usually takes 3 men and a boy and a long pole for leverage! T?C made a special rectangular jig that fit over the barrel so you could get a big wrench over it. I changed my cousin's percussion Hawken over to flintlock but it took a massive amount of effort to loosen it. Pouring Liquid Wrench down the bore and letting it sit for a few days then locked in a solid vice a big pipe wrench and a 6 lb sledge hammer finally broke it free!
I will never ever do that again.