I combine powders all the time. Most I've mixed in one batch is 48 pounds........
Once, I ordered six eight pounders, and asked for all the same lot if possible. Ended up with three of one lot, two of another, and one single jug.
Dumped them all together in a big plastic tote, then poured them back & forth with another tote like a mad scientist, til I figured they were properly mixed.
I just got done mixing two eights of current HP-38 with an older lot of WW-231. I'm set on handgun powder for a bit.
