the musket cap breech plug and nipple are in the knight catalog. all i did was call knight customer service and told them what i was interested in doing to my mk85 and they sent me the breech plug,nipple and a breech tool for free, this was 5 years ago, the economy these days may mean you pay, their customer service is great.I loved it years ago when you could call knight and ask for customer service and knight himself would get on the phone and give you advice on loads,scopes or anything. great company