45/70 for large bear... ammo?


Well-Known Member
May 22, 2012
Brookston, MN
Seems as though you're talking defense
Generally speaking that means charge, which means brain, or with a lucky miss, spine.
So punching through bone and tough mess.

Sectional density(SD) is generally used as a good way to determine straight line penetration, especially in a solid. Straight line penetration is monumental is such a situation.

.300+ sectional density is recommended for dangerous game.
A 450 grain bullet in .458 which is the diameter of your 4570 bullets will get you .306 sectional density.

So I'd look for a solid of some sort and try and stay there or above, if that isn't possible, a solid and try and get as close to .300SD as possible. 375gr bullet would mean .255 sectional density, not ideal, really not ideal if it isn't a solid.

Yes, animals have been killed by bullets with less, much less, when your hide is on the line things need a bit different look, those are the general rules. The 220gr hardcasts in a 10mm are .196 SD, the 147gr in the 9mm are .169. They've worked, but it's a bit more of a gamble then I'd like to take, especially if I have other options, which you do in a 4570.

If you can really run that 4570 to 458 win mag levels of velocity with +p rounds and you're fine doing so, you may get by ok with a heavy bonded lead bullet of great construction like a 450gr Swift A frame or a Trophy Bonded bear claw.

The Swifts can be had in 400gr as well, cuts away from sectional density at .272, but it may be a worthwhile tradeoff to get into a better velocity range with a smaller round.

The big Africa dangerous game rounds tend to allow for some bending of rules and bonded expandable lead core bullets can still get the penetration needed while also providing an expanding profile for greater destruction. But would require pushing that 4570 hard, I'd be warry of this.

Otherwise, in 4570 territory, I'd be looking solid, whether hardcast or a monometal type bullet.

Just one mans opinion, haven't had to stop a bear, sold my 4570 years ago, run a 458 lott now, I run 500gr trophy bonded bear claws.

If the moment comes, act decisively, do not waver, understand that you can worry about and deal with the aftermath, after, but you have to be lucky enough to get there first.
People have been mauled and killed because of indecision, not wanting to deal with the law, not wanting to shoot a protected species etc...

Know how you feel before going in, if you are going to hesitate or not want to use a firearm, then bring spray and only spray, because seesawing back and forth between should I pull my spray or gun, when you're reluctant or unwilling to pull a gun will render you useless, the bear will be on you by the time you make up your mind.

If you're willing to accept the consequences, be decisive if the time comes and be ruthless, stop the threat.

And you should still also have bear spray, may provide you a better out given the specific situation and the law will like that you had it.


Well-Known Member
Jun 7, 2020
All of the above from Calling 4 Life is good info. I've used 405 gr hard cast only for bear in my Marlin. Get the best hard cast out there. If you have to shoot an attacking bear it will likely be quick and real close. My eyes are old and iron sights don't work so well for me so I use a top quality red dot. Quick and easy for me. Carry bear spray up front on belt or whatever for quick access. IF a bear sees you and keeps on the approach you had better know what to do, and when to do it , very possibly no time to think. Have the proper mindset before you hunt. It must be instinctive reaction. Bear are amazingly silent, stealthy, strong and also when on the attack can go from 0- 35 mph in a blink.
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