I have a question for those much more knowledgeable on this matter than I. I have a New England firearms single shot 12 gauge. I was told that you can change barrels/Calibers if you have an SB 2 receiver. My question is, is this true? I would love to have a single shot in either 223 or even 357 magnum. If it is true how do I tell if my receiver is SB 2? The barrel is marked little partner SB 1 but it is my understanding that that’s irrelevant and all the shotgun barrels were marked SB one. Any help in this matter would be greatly appreciated.