Many of the old western cartridges all basically referred to both the caliber and the powder charge. Thus the 38-40 was a Cal .38 bullet set over 40 grains of black powder. 32-20, 45-70, 50-90, are all the same.
Modern loading of the cartridges don't always use black powder. 45-70 can be found using the original specifications (for antique guns) or way hot designed for modern firearms. Inadvertent mixing can really ruin your day. ;)
Yarddog: The 38-40 is an oddball and I am not sure how it got it’s name.
You: Many of the old western cartridges all basically referred to both the caliber and the powder charge. Thus the 38-40 was a Cal .38 bullet set over 40 grains of black powder. 32-20, 45-70, 50-90, are all the same.
Me: Sorry, but Yarddog was questioning just how the 38-40 was named. He is correct in his confusion since I don’t have a clue either. The cartridge started out as a 44-40 with the name using a 44 caliber[Actually a .430 bullet] with forty grains of blackpowder.
Then Winchester decided to neck down the cartridge to a smaller diameter with again 40 grains of blackpowder. Now the confusion. They used a a true forty caliber bullet.
So, the 44-40 is really a 43-40 and the 38-40 is really a 40-40.
You can never have too many reloading manuals.