Since no one else has jumped in on this, I’ll give it a go.

This is from notes I have made since I can never remember what the corresponding numbers are.  The information all came from somewhere along the way, so if I am incorrect on any of this please correct me.  Haven’t added anything on 50’s yet.
Bob

40, 45 and 50 Caliber Cartridges

45-70 = 2.10    .500 base
45-90 = 2.40   .500 base
45-100= 2.60   .500 base
45-110= 2.875   .500 base
45-120 and 45-125 = 3.250    .506 base. Both the same externally.

40-63 and 40-70  Ballard, Both are the same size externally.

44-70= 2 1/4 bottleneck, this was also used with an express hollow point bullet by Sharps.

40-50-265= 1 7/8 Straight case
40-70-330= Sharps 2 1/4 Bottleneck case
40-70-330= Sharps 2 1/2 straight case
40-90-370= Sharps 2 5/8 Bottleneck case
40-90         = 3.25 Straight. ?on length

32-40 win= 32 - 2 1/2, this numbering was on a Hepburn Tony Maddox has.

Oldbee wrote on Oct 7^th, 2025 at 6:17pm:


A chamber cast would tell you a lot, but IIRC .45/70 Gov't and .45-2.1" are different names for the same cartridge.

One of the best gun books ever published. Tons of information. Easy to read print. Cheaper and takes up less space than a PC and way better in bed. 

Thank you all for your input to this thread.  I am headed to the Syracuse gun show next Saturday and will be looking for a copy of  Cartridges of the World.
My interest in this subject was inspired by a Remington Hepburn a local gun shop has.  The rifle was marked as a Remington Ballard, 50 ca.  The bbl was marked 40-2 1/2.  I told the owner it was a Hepburn and I thought it was a 40-82, but was not sure.

For the .50 calibers 
.50 1- 3/4"   is  .50-70 
.50 2- 1/2"  is  .50-90   and 
.50 3- 1/4"  is  .50-140 
For the Winchester  .50 calibers they didn't go by case length just powder charge weight and the  .50-140 is actually a Winchester developed cartridge. It was mainly sharps that went by case length and others like Remington when they chambered the rifle for a sharps developed caliber.