Actually, it is more complicated that just three levels. Factory loads are in the 18,000 CUP pressure range, as are several Level I loading manuals, yet the SAMMI spec is 28,000 CUP and some manuals use this for Level I loads. Level II loads vary with the particular manual too, some using 28,000 CUP and some using even higher pressures. Then for Level III loads, some manuals use 40,000 CUP as the maximum while others use up to 50,000 CUP as the maximum. After over 130 years the .45-70 is still not so well understood. :roll:
Keep the Shikari loads under 27,000CUP and you'll be fine. I've had mine for 32 years, used only loads in the 20,000 CUP class, harvested a few deer and a black bear, and the rifle is still tight and accurate. A 300-grain HP at 1850 fps is plenty for any deer, and a 405 FN at 1700 fps is plenty for almost anything else - all at 20,000 CUP or less. The latter load is not very pleasant to shoot in the little Shikari... :twisted: