Cartridge Delima 50-70 Government or 50-90 Sharps

[Sedalia Dave]

Looking for opinions of which cases I should cut down for my Springfield Armory Conversion Spencer.

The chamber is 50 Cadet which was based on the 50-70 Government. When i was looking for cases to cut down I couldn't find any 50 Govt but did find 50 unfired Starline cases in 50-90 Sharps. I was unaware that the case dimensions for 50 Govt and 50-90 Sharps are slightly different. While the rim diameters are almost identical, the base diameter not even close.

50-70 base diameter is 0.565"

50-90 Sharps base diameter is 0.585"

That is a 0.020 difference. One would think the cut down 50-90 Sharps brass wouldn't fit into the chamber cut to 50 Cadet dimensions but he cases dropped right in with no issues.

I discovered this when I was making dummy rounds for my newly acquired rifle.  My 0.511" sized bullets slid right into the cut down 50-90 Sharps cases. I attempted to run them into my RCBS 56-50 sizing die but the case would only go in about 1/3 of the way before the force required made me stop. So I started doing some research and discovered the above difference in base diameter.

My question is should I continue to use the 50-90 Sharps brass or source some 50 Govt brass and cut it down. I started with 50 cases and still have 30 that I haven't cut. Starline is taking back orders for both 50 Govt and 50-90 Sharps brass.

My gut says to stick with the 50-90 Sharps brass as it fits the chamber better and I may get less blow by. What do you all think?   

[Coal Creek Griff]

I haven't crossed the particular bridges that you're crossing with this project, but I've worked with a couple of somewhat unusual chamberings. Do your cut-down .50-90 cases chamber in your rifle? It sounds like they do. If so, I'd tend to agree that you can probably make them work as long as they don't require full-length resizing.

[El Supremo]

Hello:
Fascinating stuff.
I have three different lots of STARLINE 50-90 SHARPS brass and each has the same rim OD of .660" and body OD at rim of .559" - .560".
I see the Wiki dim for 50-90 Sharps of .585", but there is no longer a SAAMI drawing for the 50-90 Sharps.  Per Howell on page 407, the 50-70 Gov'.t base at rim OD is .570", but he noted a .568" variation. 
Based on my three lots of Starline 50-90's, you might want to verify 50-90 dim's with Hunter Pilant, Process Mgr and Chief Ballistician, hunter@starlinebrass.com.
Please keep us posted. Thanks and smiles.
El Supremo/Kevin Tinny   

[LongWalker]

FWIW (probably not much), I used to shoot a Springfield rolling block carbine in 50-45.  My brass was made from .348 Winchester cases, which worked fine with the extractor.  Brass made from DGW 50-70 cases had to have the rims reduced in diameter (not sure how much, lacking lathe access at the time I just filed the rims til the cases fit). 

[Sedalia Dave]

I haven't crossed the particular bridges that you're crossing with this project, but I've worked with a couple of somewhat unusual chamberings. Do your cut-down .50-90 cases chamber in your rifle? It sounds like they do. If so, I'd tend to agree that you can probably make them work as long as they don't require full-length resizing.

No matter which brass I choose I intend to buy a set of 50-90 sharps dies. I have a friend that can cut down the seating and crimp dies to 50 Cadet length.
I'll leave the depriming die as is. That way if the cases need a full length resize It will be easy to accomplish. This is definitely a BP only rifle so I am not worried about bullets sliding back into the case. However, will use my existing 56-50 dies to do a neck sizing so that the bullets have some neck tension.

The reason for not buying 50 Govt dies is that the crimp die is not the correct dimensions. 50-70 Govt bullet neck diameter is .535. While the Sharps is .528. Lyman makes their 56-50 dies by cutting down 50-70 dies. This leaves the crimp die too large for most 56-50 rifles. My Lyman dies will not apply a roll crimp but rather apply a taper crimp to 56-50 cases using a .511 bullet.

[Sedalia Dave]

FWIW (probably not much), I used to shoot a Springfield rolling block carbine in 50-45.  My brass was made from .348 Winchester cases, which worked fine with the extractor.  Brass made from DGW 50-70 cases had to have the rims reduced in diameter (not sure how much, lacking lathe access at the time I just filed the rims til the cases fit).

Thanks for the info.

I am shooting these in an original Spencer action that has the blade extractor on the left hand side of the receiver. I need the rims to be the same size or a larger for reliable extraction. When I first got the rifle I experimented with 56-50 (Taylor's) brass and had a few failures to extract because of the smaller rim diameter.

I was worried that the rim diameter of the 50-90 Sharps brass would be too big and I would have to cut them down slightly but they chamber easily.

[Dave T]

As an owner and shooter of a Shiloh 50 2-1/2 Sharps Straight (50-90 for this discussion) this seems like a waist of perfectly good brass.  However, ya gotta do what ya gotta do so best of luck to ya.  (smile)

Dave

[Coal Creek Griff]

It sounds to me that you're on the right track!

CC Griff