We Use a type of Alloy called Linotype Alloy Ingot (4%-Tin, 12%-Antimony, and 84%-Lead) it is antimony and tin with lead you can get pre mixed or just the lead and antimony part for easier storage just mix into lead at desired ratios, can do this on a wood fire if you have to and cast the ammunition.
As for cheap corbin stuff you can find it at meets for guns and out door stuff a lot of guys buy it and never use after first time because cheaper and faster to buy pre done.
getting a progressive machine and multi set up for pistol and rifle is the best if you have $ to spare saves on changing out the machine all the time.
Dillon makes decent reloaders but the assembly instructions are worse than IKEA assembly written in Egyptian hieroglyphics
if you get one look and learn it now on you tube and feel the others pain before it becomes a dire situation.
But on plus side they are fast the 650 just get electronic primer flipper saves you aggravating time doing that.
as for lighter materials a long time ago a company called aguila made a bullet called IQ it was an alloy of extreme light weight 117 instead of 230 with a muzzle of 1800 fps.
demo of how to melt copper
This looks like interesting bullet