A friend just gave me a jug of powder. He had no info on it, just said he had it for a long time and doesn't reload anymore. The jug says Magnum Rifle Powder MR-3100. Made by the Sonday Powder Co., Lake Villa Ill. 60046. I've searched the internet and can find nothing about it. Any ideas?

You lucked out. MR-3100 is now known as AA 3100. You can use the data for AA 3100 or IMR 4831. It's one of the all time great powders.

Thanks,
I'll give it a try, hopefully it's not to old.