RCBS 45/75 dies not correct

[postman63]

Took my new Cimarron to the range to test fire today. I found the Jameson brass, and the RCBS dies do not comply with my chamber. After firing, we noticed the angle of the shoulder was changed. It had been fire formed out so that the shoulder begins farther up the case, and makes the angle steeper. When I got home I put one through the die to see how it fit, and it puts the shoulder in the same place as Jameson but there angle is less steep which makes the neck a bit shorter. So the dies make the neck the same as the chamber but the shoulder and angle are different. will try to post pictures so you can see.
Left is the new Jameson brass, Middle is the fire formed brass, Right is the RCBS sized brass.

[Shotgun Franklin]

Then you might try neck sizing only. If your is the only gun this ammo will be fired in.

[Trailrider]

Do the RCBS sized rounds chamber okay in the rifle? If so, you have several choices: You can go with the resized cases fireforming again, which if severe may work harden the brass quicker. (From the photo, it doesn't look like there is much difference between the fireformed case and the RCBS resized case.) You can, as Shotgun Franklin suggested, necksize only by backing the sizing die out until you get neck sizing only. You can fireform 3 brass cases, and send them to RCBS and have a custom die made up (probably somewhat pricey nowadays...I haven't ordered one in years.). You might also want to make a chamber casting out of CerroSafe low melting point alloy (Brownell's or Dixie Gun Works), and send it with the fired cases to RCBS.

Hope this helps.

[FriscoCounty]

AH, looks like you are running into the Uberti .45-75 vs the SAAMI .45-75 problem.  Have a look at the threads below, they should help you determine if that is the problem.  Basically, for a long while Uberti used a non-SAAMI version of the .45-75 for their 1876.  The upside was that it held more powder.  The downside was you needed a special full length sizing die or only neck size the fire-formed cases. 

Frisco.



http://www.cascity.com/forumhall/index.php?topic=41632.0
http://www.cascity.com/forumhall/index.php?topic=39200.0
http://www.cascity.com/forumhall/index.php?topic=31742.0

[postman63]

Thanks for the input guys, I have already sent an email to RCBS about the problem. After doing that I found, in their FAQ a note about sending in dies and fire formed cases. It said they would check the die to see if it was cut correctly, and fix for free if it was done wrong. If its right they will custom cut the die to fit for a fee. Since there is no SAAMI standards for the cartridge I don't see much chance of them saying its wrong. I am going to do it to find out their price for custom die's. Then decide whether to neck size or have them make one.