A little update here. I bored the grooves and nose tonight on the 12 ga mold, but when I took it out, I had lots of chatter marks on the cavity. I made a rough sprue plate and cast some anyway.
http://f2.pg.photos.yahoo.com/ph/castboolits/detail?.dir=/c2c8&.dnm=3f83.jpg
It looks like fortunecity isn't allowing me to link to pics anymore, so I put a pic of the cast slugs on the yahoo castboolits page.

I had to make a rough estimation of weights by hanging 500gn boolits on the end of the scale. I'll have to make some actual weights later.
.885" 740gns
1.485" 1330gns
1.68" 1520gns
1.87" 1700gns
2.05" 1960gns
2.43" 2300gns
Cast from Wheel Weights

I'm thinking that I might try makeing a dual screw vise and cut another one with a cherry. Anybody know of a place to buy a vise suitable for this without makeing one?

I could make you a 10ga one, but it won't be pretty until I learn how to bore without chatter.

It looks like rocky mountain cartrige has some 3.5" 10ga brass cases. $50 for 10.