I am wanting to start reloading cast bullets for my 45-70. I found a semi local source for 350 grain cast bullets that are 92% Lead -2% Tin-6% Antimony (Brinell Hardness Number 18-20). I am shooting a Marlin 1895. I don't know much about Brinell Hardness, other than the higher the number the harder the bullet. What would be about the fastest I could drive this bullet for hunting applications? I am not looking for a screamer, just wanting to know. With a bullet of this hardness will there be expansion or none at all? I am wanting a bullet such as this so I can afford to practice more, with a bullet I will hunt with. Thanks for any help.

I'm assuming that it is not a gas checked bullet. If that bullet design is of the bevel base type that so many commercial casters use, you may get some blow by of gases with that hardness rating. That will result in leading of your bore no matter what velocity.

Otherwise, I'd try running it at 1700-1800 fps., and see what happens. Doubtful you will get much expansion with that hardness, but how much do you really need?

Best of luck with it!

Make sure the bullet is at least groove diameter, and a little larger won't hurt.

For hunting you'll want it to have a large flat meplat. I don't think you'll get much expansion, and with hard cast bullets it's the flat front end of the bullet doing the work. An LBT style flat nose profile busts things up much more than a round nose or a typical commercial truncated cone with the edges of the meplat radiused into the ogive.

For example these nose profiles are what you want to whack things hard:

http://www.laser-cast.com/images/TSthumb_45-70-430fpgc459.gif

http://www.castperformance.com/stores/c/castp/catalog/6295-l_thumb.jpg

http://www.lbtmoulds.com/images/458cal.gif

Good advice on the two previous posts.

Marlins run well with bullets sized to .460"

How do you know which size groove diameter to use?

gas checked and 1700 FPS will kill anything your likely to encounter.

You can slug the barrel, measure it, and go .001 to .002" larger with cast bullets.

I go at least .459" in my rifle, and it really likes .460"

Very, very true...

You can bore through a lot of animal with that load.

I have shot cast at the velocity and they did not shoot well (no gas check) but loaded it down to modest velocity (I think it was 1200 or so)and got great accuracy.

1700 may be a little fast for a BB bullet. Probably had gas cutting issues. I'm thinking 1450 to 1500 would be as fast as I would push a non GC bullet.

A 405 at 1200 will still penetrate quite well.

My 500 were Lee with gas checks, but 400's at 1500 did not lead and they were linotype dropped into water to harden.
Randy