You can, if the right chamber was cut in your rifle , just run 45-70 cases thru the size die. Most of them tho need to be sized then trimmed to length.
It won't really be much cheaper to shoot, unless you stick with the original 265 gr bullet weight.For the most part it does it's best work with the 400 gr bullet. I have also sized down the lyman 412263 bullet and shot it in the 40-65 for a good short to midrange bullet.
It's a good cartridge for hunting and for majority of the bpcr shooting.