50-70 Government Cases to 56-50 Cartridges

[paledun]

When I purchased my Burnside Spencer for Cowboy Action Shooting, the wife included a number of 56-50 rounds that had been loaded by a prior owner (may have been her husband or others).  They were all approximately 1 1/2 inches in length with a flat, hollow point bullet.  As a batch, they were of differing case length and all badly corroded.  I pulled the bullet on one to find smokeless powder and went on to pull the remaining bullets.  Case length went from 1.14 to 1.172 inches and the bullets measured .512 diameter.  While I did not chamber them all before pulling the bullets, those I did chambered nicely.  The longest case, 1.172, also chambered nicely after resizing.  I also received 20, 50-70 cases that had been fired once or more and am considering trimming them for 56-50 loading.  My current Spencer load is a Starline case with a Lyman 340 grain RNFP bullet over 39 grains of 2F.  This load with a length of 1.51 overall length actions easily and works well for CAS.  The load is not optimum for extraction because of the rim diameter.  THIS IS MY QUESTION, would it be possible to lengthen the 50-70 case to 1.65 or so and maintain the overall length of 1.51 inches?  I am currently attempting to crimp on the top of a lube groove and would rather crimp further up the nose of the Lyman bullet.  Your thoughts please.  Paledun

[FreddyC]

1.65" for the 50-70 trim? I'm sure you meant something else since your desired oal is 1.51". Since it is a rimmed cartridge, I think you can custom trim your 50-70 to whatever length works in your rifle and for your particular bullet. Cut one and try it, as long as your charge is slightly compressed and the round feeds,chambers, & extracts you should be good. Try 2 though because one round in the mag will almost always chamber but with 2 in the mag, you will be able to see if your loads are being seperated properly by your breech block. My 1865 loads must be 1.565, give or take .003 or they will not feed. You might have to trim some brass off of that 50-70 at the mouth because it is thicker walled brass and the bullet may bulge the case making it tough to chamber.

[paledun]

Thanks FreddyC for your response.  My mistake, I dropped a "!" somewhere.  I did mean 1.165 for the trim length of the 50-70 case.  I will continue to use the overall cartridge to 1.51 inches using a 340 grain Lyman bullet which chambers nicely and extracts very well.  My concern is crimping on the top lube grove of the Lyman bullet with a case sized to 1.151.  I made a dummy cartridge with a 50-70 case at 1.165 and it chambers nicely.  Any thoughts about case extraction or pressure with the longer case?  Thanks, Paledun

[FreddyC]

I  think pressure would not change at all, as you are simply covering more of the bullet with the taller case. Starline extracts great in my original 65 carbine, but I think the 50-70 rim is supposed to be optimum for the Burnsides and 1860s. I load with BP but currently am loading 9.5 gr of IMR Trailboss smokeless with the 350 gr Montana Bulletworks Spencer bullet. I load these for my local indoor range shooting. I know everybody freaks out about smokeless in these old rifles, but this load is very mild and accurate, just for fun shootin. Good luck on your handloads

[Herbert]

If you look at the pressure charts for Trail boss you may want to rethink using it in original Spencers,though the velocity is low the pressure is not.TB is mearly a balkey fast pistol powder,its burn rate is extreamly fast so pressure peak is quick and high,somthing you do not need in a BP rifle were there is very little suport of the cartridge next to the extractor.Even in its day this was reconised as a weakness in the Spencer,the Lane type extractor partialy fixed this ,the NM with the short blade extractor has the best cartridge suport of any of the Spencers