So far I've only cast the Lyman 525gr 12ga shotgun slug and I use extra hard 6% antimony. (It seemed like the obvious choice for a shotshell reloader).
But now I'm thinking about casting some real bullets. Is this lead a bad choice?

If it matters I was thinking about the Lyman #457193 420gr at 2000fps or so in my 45-70.

That seems a pretty fearsome load for 45/70 !! The 457193 is a plain base design sans gas check and would suffer serious leading problems at that velocity.

Top loads in 45/70 can be best achieved with a gas checked design or using pure lead with a paper patch. Get hold of Paul Mathews book "40 years with the 45/70" and "The Paper Jacket" by the same author for in depth loading techniques.

That velocity was listed in the my Lyman reloader book so I assumed it would hold a gas check, thanks for pointing that out to me!
I guess I'll have to get a mould catalog with pictures and arrows to help me pick another one.

But what do you think about using shot for casting? It seems like it would be a consistant pure alloy and readily available. Am I missing something here or are people just focused on using free lead?

I cast about 500#'s a year, so using shot would be cost prohibitive, to put it mildly.

you can use lead shot to inrech the bullet metal. You will still need to use some tin to fill it out . If useing a gas check 2000fps should not pose a problem Lee makes a 340gr target 457 mould. That I cast for people shooting at that velocity. Go to my web site to look at it.

chevota...It's not a bad choice but may be a little harder than you need for what you're doing. I'd melt the shot and add a little pure lead. You may need to skim off a little of the antimony which will appear a a frothy coating on top of the mix before adding the lead. This should be saved for hardening softer alloy at a later date. You may or may not need to add tin. See how they cast first and omit the tin if you get good fill out as tin is $$$$$$.

2,000 FPS with a 420 grainer is pretty ambitious with a PB bullet. I'd go with a 45-405-FN RCBS with a gas check which will finish out about that weight and should allow you to make 2,000 FPS if you're into pain./beagle

Cool, thanks for the info everyone. If I ever pick out another mould (busy) I'll try the pure lead and the tin idea to see how they all work out.

That Lyman cast just looked like the best choice for me until Eric set me straight. I'm sure I'll end up using jacketed for the real high speed stuff to avoid leading, but I still want a potentially powerful cast to play with.

beagle: It's all just for fun, I won't be sitting at a bench shooting 100 rounds so I think I'll be alright. Plus my dominatrix will punish me if she sees bruises that she didn't inflict. Hmmm, now would that good or bad??

Keep in mind the arsenic content in the lead shot. Melt in a well ventilated area. If you can smell it, you have too much shot melted, and WAY too much arsenic in the air. Have the neighbor kid do your casting for you.

"Have the neighbor kid do your casting for you"

Say what Ric?

waksupi:
Thanks for the tip, I'll find a kid. He he....