Shgeo,
Thanks for the tip. I don't usually buy commercial cast; when I bought the Marlin Guide Gun, I asked for freebies. I got a box of 300 grain cartridges and a few bucks off of the cast bullets, or vice versa.
I'm not at home now, but I think the box of 500 I got was from Laser Cast. They are the exact profile 405 grain slug I will be casting for myself.
This idea of silver is new to me; I just saw an advertisement in a gun magazine. I figured if it was really silver, the content must be low. I use the traditional lead, arsenic, antimony and tin. I've been doing it for so long that I mix 'by eye.'
I have two 42 pound pigs of lino I got from an old printer; I was saving them for use in a rifle. Now is my chance. I'm hoping for more than 1,000 fps.