Garry, from the looks of the Swiss powder load, I'd probably stick with BP, with some experimentation around charges, ie; down to 110, change the wads and try similar bullets of slightly different weights just to see how your rifle responds.

More shooting with that exact load is also required - averaging 4 or 5 targets is much more accurate than a single target, of course.

Looking good so far with BP.

In some guns a reduction of recoil produces higher impacts, in others, lower.

In this case, it appears your gun shoots lower and diverges with less recoil.

Be very careful about not canting the tubes while shooting and that will cause diverging/crossing and elevation changes as well.