10 drams won’t be too bad from a heavy rifle such as yours.
I’ve shot 240grs in my single barrel muzzle loader and it was quite tolerable. The “service load” for the 8bore muzzle loaders was, I believe, 300grs but I haven’t got there yet.

I don’t really know if breech loaders recoil more or less, generally, than equal bore/charge front stuffers.