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
"Not in an open forum, where truth has less value than opinions, where all opinions are equally welcome regardless of their origins, rationale, inanity, or truth, where opinions are neither of equal value nor decisive." Ken Howell
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