Tim, i have the same brass powder measure.......came with a Thompson renegade that i got from my late friend bill.
the following is an bit of an email that i received recently from GOEX.
"You can load 70 grains of 2f or 3f, or Cartridge in the 45-70 with any bullet weight between 293 and 540 grains with no safety issues whatever as long as the rifle is in good condition. Powder charges above 65 grains will be compressed with the heavier bullets.
Two things are important. One is that the cartridge be loaded without any airspace between the bullet and the powder, and the other is that you need to be sure to use a dedicated black powder lube on the bullet. Otherwise fouling will be significant and difficult to remove.
Sincerely, Bill Bagwell"