I am getting started in shooting black powder cartridge rifles and in turn learning to cast my own bullets. I have a couple of questions.
1. Alloy, how do I determine what bullet alloy to shoot?
2. Sorting bullets by weight. How close do you sort? I see some people sort +/- .1 grain, some by as much as a grain.
Thanks for any input.

I use 30:1 lead/tin, most here in the Fire are fond of 20:1.

If shooting paper patched use pure lead or pure with a touch of tin to aid mould fill out. 60:1 will work, but so will pure.

I sort by weight. No grouping with a range of weights.

Bullet alloy choice is going to be dependent on your rifle barrel, caliber/velocity, and bullet design. My .45-70 Shiloh Sharps likes 20:1 with the Lyman design greaser bullets I'm currently shooting.

Some folks like 30:1 for better obturation, but you are running into the possibility of nose-slump at that level of softness.

I'm sorting to 0.5 grains, mostly because my current shooting ability cannot use a finer degree of difference. Using the Bell curve, I keep those within 2 grains as my precision choice and anything over 5 grains goes back in he pot along with any that are deformed in any way. Between 2 grains and 5 grains are my "plinking" and warm-up bullets.

Ed