Ray,
We seem to have similar experiences with wheel weights.
Perusal of the various shooting/BPCR websites one can always find someone who regales others about their ability to shoot high antimony content lead bullets. My rifle experiences have been with those having deep rifling made especially for cast lead/tin bullets. Bullets with antimony don't like to fill out the lands of the deep rifling.
Have known a number of bullet casters in my travels and most produced strictly handgun bullets. Virtually all casters start out without a thermometer (budget constraints/thrift/just plain poor) and easily run the melting pot full blast at maximum temperatures, unaware that the tin is being vaporized.
The website Lead Pot referred to is great information, but dated and excludes most of today's available scrap lead combinations. It especially addresses handgun bullets and NOT those that are in common use with BPC Rifles. Walking around trying to find scrap lead, linotype, plumber's lead, cable sheathing and lead plate battery residue is no longer common. The larger the community, the more difficult the situation.
We live in a nation of laws and rules. The OSHA, ANSI and other unified rules pertinent to lead and lead mix products are serious business in industry and should be thought of in a like manner whether one lives in the heart of a large city or out in barren prairie or desolate mountains. It all boils down to known health hazards. Many of which bullet casters schrug away as meaningless.
Folks seem to pick and choose what laws/rules they want to comply with or ignore.