The Lyman 48th edition loading manual has data for all of the sharps rounds. I would have to reccomend that you stay within the SAMMI spec max of 28,000. American factory ammo isnt any joke out of those long barrels and it is only 24,000. In 45-70 govt. in the lyman manual with a 535gr bullet you can get 1500fps with a 30" bbl. Thats whoop ass! Good enough for africa if the bullet wasnt soft (not sure id use a singleshot on dangerous game though). Just food for thought.