.45-75 Win Brass Dimensions & Forming Choices

[Earl Brasse]

Happily I have finally acquired one of my long-time gun-wants, a Cimarron 1876 N.W.M.P. carbine in .45-75 Winchester.

Now on to feeding it.
Finding or making cases is a bit tough.


Lots of Pards have posted on this & other sites I have found how they are using "X" brand or case for .45-75 Win.
Most, even though using different cases, say "X" "works well" & "have been doing it for years".
Great to hear, no wrong answer, some decisions most likely made on price, availability, ease of production.
I thought it would be useful to gather up some information to help understand the possibilities.
All of the gathered info. is read & use at your own risk.

Rocky Mountain Cartridge Company, correct headstamp, expensive but available?
Jamison, out of business, you have to be lucky, if you find it, buy a Lotto ticket, you're on a roll.


There is a bit of variance on the exact case dimensions depending on the source:

                        OAL: 1.86 to 1.88"
                       
                        Rim Dia.":  Rim Thickness ":  Head Dia.": 
Cartridges of the World   .616      xxx               .559

Designing & Forming Custom Cartridges for Rifles & Handguns by Ken Howell
                         
                          .629      .062              .546
The Home Guide to Cartridge Conversion, Nolte, using WRA Headstamp example .45-75 Win. cart.
                          .624      .070              .562
                         
 The Handloaders Manual
of Cartridge Conversions John J Donnelly uses the same info from Cartridges of the World

Keeping in mind the above, on to possible candidates for case forming:
All new, unfired brass

NOTE:
New Jamison has a wide & deep extractor groove.
Factory Winchester has no extractor groove.
Personal thought, it didn't back then but it does now, but it's a good thing.

                     Rim Dia.":  Rim Thickness ":  Head Dia.":

Jamison.45-75          .614          .059             .556
Starline 50-90         .650          .060             .558
Starline .50 Alaskan   .600          .065             .545
Winchester .348        .603          .061             .547

Personal observation, a .50-90 .650 rim is too big to cycle thru the action but if trimming to factory Winchester .629 works, I would think it would be better than .600.

Wish I would have bought a '76 earlier, lol

[Black River Smith]

I hope this helps you in this early phase of learning.  The Cimarron rifles are not designed to the Winchester specs.  Period End.  I suggest you read a lot more before starting to buy and cut and size any brass.

I make this statement when I do not have a Cimarron rifle but a Chaparral which was design to be 'about' the same as a Winchester.  Also, I have the 45/60 not a 45/75, but I have read most of the posting in this forum.  I read peoples issues with the brass alterations for both cartridges.  I also tried to reach the Winchester 0.629 rim diameter for my rifle.  From experience don't bother to try that.

The statement that seems to apply the most for Cimarrons are the bolt face/size was made to 'more easily' correspond to the rim dimensions of the 45/70 casing.  One last thing that I know from the postings, Cimarron had two different Chamber cuttings for the 45/75 shoulder.  You will have to figure out what one your rifle has.  Sorry, I do not know the details/dimensions of these two different chamber that where used, or the manufacturing timeframe for each.

If you read through the many pages of posting you will see all the trials and errors of the many posters.  You will eventually find the answers that you need; the techniques to get to; and maybe even the correct dies to buy, in order to get a Cimarron usable cartridge.

READ A LOT MORE IN HERE.  My best advise.

[Earl Brasse]

Yes, thank you for your insight, deleting post as it offers no new information.