Kombi,
Those heavy Garrett .45-70 loads are commonly used in modern Marlin 1895 lever action rifles. That model was made in microgroove Marlin type (12 shallow grooves) and "ballard" type (six deep grooves) rifling. The deeper rifling is better suited for lead bullets and heavier loads. That is, it's much easier to get good accuracy from the standard deep groove rifling.
HTH
John
