Is there a reasonably universal annealing temperature?

[Naphtali]

I have a large bucket of bullets that were hard cast many years ago. I own no hardness tester and do not know the alloy. I appreciate the bullets' shape and want to use them. Is there a reasonably universal annealing temperature for hard cast bullets? My intention is to anneal the bullets then heat treat small batches at increasing [incremental] temperature until I am satisfied with result.

[Ricochet]

425 F for an hour, followed by slow cooling, will do it. Linotype melts circa 475 F, so you want to stay well below that if you don't know what you've got.