Congrats I think you made a Great Choise in guns , My KRB7 shoots Great
with loose powder start with 85gr and you can work up in 5gr increments

In a conical I shoot 85gr 2fg 777 loose a Bullshop 445gr UC Short with a .510 pver the powder wad

In a Saboted Bullet I shoot 85gr 2fg 777 loose & a .430 44cal 300gr XTP with a harvester Green Crush Rib Sabot

Keep us posted on the progress !

Ron