Just knowing enough to be dangerous, your components are top notch as is your builder. I like the Mausingfield action. Seems very well thought out. I've wondered about Proof barrels as I've heard pro and con. I'm a Bartlein and K&P guy but it seems like the salad days of great barrel makers out there. You'd have to really try hard to get a bad one.
SAC is just a great builder. My Scalpel is inbound to him now for some minor work.