H&R will tell you that levergun loads are fine, but most find even those too stout, specially without any recoil modifications. I shoot wood stocked .45-70s only, either lam, or walnut, they all have a Limbsaver recoil pad and I use either a 2lb lead pipe or lately, a 1lb mercury recoil reducer in the stock bolt hole for bench work, the recoil of the 300gr Nosler partition at over 2400fps is just about equal to the recoil of the 375 H&H.
Tim