100 yards should be no problem as my Marlin 1895 will group just over an inch at 100 yards with the 1.5 to 6 Leupold and PMC 350HA +P+ ammo...This is a hot load but the rifle shoots well with it.....and at $18.45 per box it's much more affordable than most of the other hot loaded "premium" ammo......Standard Remington 405 grain loads also shoot well in my rifle, but not quite as well as PMC...the 405 grain Remingtons are about the most pleasant factory round that I've shot, and recoil is nothing near the PMC
With my poor eyes, 3 " groups with factory "iron" sights is pretty good for me......past 125 yards the bullet starts to drop pretty fast.....certainly, however, the 45.70 is capable of more in the hands of an expert.......you could practice a little and probably feel comfortable with a few yards more......loads of buffalo were killed with this round at ranges far exceeding this.......but this is one of those things where only you know your limitations......if you don't have time to practice much, I'd probably limit myself to 125 yards and certainly no farther than 150 yards..........but that's just me........others might feel they can justify shooting farther..........If your hunting bear over bait, I'd guess you won't be testing the limits of the 45.70's range, as I hear most shots are 50 yards or less.......