I use the term High Brass for any heavy game load. Presently, I hunt with Super X 1 1/4 Oz shot at 1330 FPS, so these are pretty hot loads. We hunt in pretty tall timber in our area and haven't had as good of luck with bird loads. I will also use Remington of about the same load.
Well then, good luck with the gun.
I’m curious…….did you tell your gunsmith you intend to exclusively shoot 1 1/4” loads at 1330 fps out of it? If you did, and he didn’t caution you then we can draw one of two conclusions. Either he’s unqualified to work on vintage SxS or he’s looking forward to plenty of work from you.