Can someone give me some information about cut down 50-70

[Roscoe Coles]

I am working on getting ammo that will work in my carbine and I am finding that the chamber is a bit big.  I am thinking of using cut off and unreamed 50-70 cases but I would like to know how think the 50-70 case walls are before they are reamed.  I know that there may be a problem with getting a good gas seal but I am working it out one step at a time.  The problem is that the .512 bullets are loose in the fired cases and it I resize them I will have to anneal them every time I reload them or they will quickly fail.  On the other hand, the mould that is on loan seems to be the fix to the feeding problem as they feed great through the magazine. 

I may have to go to a larger bullet to make the cases work.  Rapine makes a .520 350 Spencer bullet but this is a bit big for the .512 bore (.515 would be fine but I'm not sure about a .520) Its possible it would work with the small driving bands and the huge grease groves.


Anyway, can anyone tell me the wall thickness of the 50-70 case when its cut off for the Spencer and before its reamed?


Thanks.

[Tuolumne Lawman]

I used the Dakota Widow Maker / Hell R Highwater modified 350 grain LEE mold unsized at .515.  Worked awesome!  It worked better unsized than sized to .512!  I used Starline brass.

[Roscoe Coles]

Thats the bullet I am using but its casting .513 with this alloy, the trick is after firing the cases measure about .520 at the mouth.  Remember, mine is an odd duck and I am trying to make a large chamber work so I need some measurements so I can make some decisions about what would be best.  Anyone have the data on the cut 50-70 on hand?

[El Supremo]

Another approach might be to call Dave Casey at Rocky Mountain Cartridge, 307-587-9693.  I have been told that he can turn cases to whatever reasonable internal and external dimensions might be needed.  You would have something that really fit both the chamber and bullet that matches your bore.

Regards,

El Supremo

[Roscoe Coles]

Well, we are a long way from there at the moment.  I am going to see what the case thickness is like for 50-70 and .348 win to see if they would be thick enough to take up the space I need then look at larger bullets.  The chamber is actually about right for the original case measurements for the 56-50, which had a great deal of crimp (in fact Spencer didn't like this and developed the 56-52 to get rid of what he thought was excessive crimp in the 56-50, which was developed at Springfield Armory).  Anyway, we are working in the right direction, it feeds, fires and ejects.  Now wear are in the "make it shoot well" stage that can get so interesting with older guns..

[Fox Creek Kid]

The case walls will be thicker on a cut down 50-70, hence the need to inside ream them to accept an ORIGINAL diameter Spencer bullet.

[Roscoe Coles]

Yes, I understand that the case will be thicker and that in a modern SAMI spec chamber you need to ream them to get the bullet to fit.  However, this chamber is larger than SAMI spec, and more like the original 56-50 chamber so I am trying to use the thicker case wall to my advantage to take up some space in the chamber.

Here are the numbers.

I am using a .513 bullet and the case thickness on the 56-50 brass I got from Buffalo Arms is .011 at the mouth.  So, even without a crimp the loaded cartridge will be app. .535 at the cartridge mouth. 

The chamber on this gun is .551 at the cartridge mouth so I need to make up app .014 to get a properly fitted cartridge (somewhere about .549 at the case mouth would be good).  So, if the cut off 50-70 cases are .018 thick before reaming then I am home free. (.513+(2x.018)=.549).  If they are more than that I can make a reamer of the appropriate size and ream them to what I need.  If they are not thick enough I will try the .348 win.  if that does not work I can go to a bigger bullet.

One step at a time, at this point what I need is the thickness of a cut off 50-70 case prior to reaming.

[Arizona Trooper]

The bad news is that unreamed 50-70 cases vary all over the place, depending on who made them. I have some old Dixie brass that I might not have reamed yet, and will measure it tomorrow. But that won't help if you have Bertram, Starline or other brass. They will blow back a lot when unreamed, and it's really hard to get them annealed right. Good luck!

[Bead Swinger]

My suggestion would be to go to Buffalo Arms and get a sample of their 56-50 brass made from Starline 50-70's.  Then anneal the cases.  I had very good luck with thier 56-56 cases, and I'd assume that their 56-50's would work well. The nice part is that they come cut, reamed, and with the base reamed, and if they work, you can get lots of them, or copy them from available Starline 50-70's.

[Tuolumne Lawman]

+1 on the BAC cut down and reamed brass.  I used it on the 56-56 I had, and it sealed well.

[Roscoe Coles]

Interestingly, when I got the 50-70 brass from Starline and cut it down, it was not significantly thicker than the so called converted stuff I bought from Buffalo Arms (which is supposed to have been reamed).  Less than half a thousandth difference.  I was hoping for something more significant.  .348 cases are a bit thicker but I would have to turn the rims down as the rims are to thick (the diameter is actually smaller than 50-70).  I think I will have to look at a bigger bullet and see what it will do.

On the up side, the bullets cast in the modified Lee mould loaned to me feed fine.  I don't have enough cases at the moment to make any determination on accuracy.  I have just been working on function firing.  I think I will have to look at the bigger (.520) Rapine large grease grove bullet, but until I have the cash to buy one, I will plink around with the bullets I have.