I've just started looking at deer loads with the 458 Win Mag using 45-70 loads.. I'm also dealing with brush in my woods. I want a flat nose bullet. Since deflection is proportional to velocity & inversely proportional to weight I want a slow & heavy projectile.
This is preliminary:
I have gotten decent results with Berry's 350 gr 45-70 round shoulder. It is a plated bullet 0.459 inch diameter, with a 1950 fps maximum. It should be fine for deer. Since it is basically a cast lead bullet with a thin copper plate, like a cast bullet it should expand at low velocities. Unlike a cast bullet there are no issues with lead fouling. I'm leaning toward this bullet.
I also have Hunters Supply Slick Coat 45 Caliber 295 grain HP Lead Bullet, also 0.459 inch diameter. A smaller flat point with a big 5-sided hole in them. I've tried a couple with mixed results, it isn't grouping well but I've only tried 1 load. These may be OK with more work. I'm wondering if this will fragment excessively.
I just got some Lehigh .458 caliber, 380 grain Wide Flat Nose Lead-Free Bullets. I haven't shot them yet. It'll probably be a while before I can (broken firing pin). It does look interesting, though it is probably a better option for a long flat shooting round in the Win Mag. Lead free solids need high velocity for expansion. But this should make a big hole even without expansion.. The Berry's is only slightly lighter & seems to be a better option unless hunting in a lead free zone.