.50 70 Government reloading

[orpington]

First, see the following:

http://singleshotexchange.com/handloading-the-50-70-for-a.html

The author talks about reloading this cartridge and states that he is using undersized bullets at .512", and he states that original military rifles are .515 to .518. Undersized bullets lead to inaccuracy. I slugged a Sharps 1867 Cartridge Conversion this morning and I obtained the following: Land diameter .522, Groove diameter .541. The grooves and lands are distinct (6 grooves) so, a total difference of .019, or ~.0095 per groove vs land is probably about right. The bore is in good to excellent condition. Has anyone else experienced this as this is far greater than anything else I have read about? In the old days, may an ~.512 pure lead bullet been fired, and it would expand to bore diameter, leading to accuracy? Where do I go from here? Need ~.542 or .543 bullet, but don't know if cartridge will load properly, either while handloading or chambering the cartridge. The date 1863 is on the barrel. I load using Fg black powder.

By the way, firing a .512 bullet means that I can rarely (!!!) hit a target at 50 yards.

 

[Malamute]

Get the material to do a chamber cast*, and it will tell the tale of what will chamber and what wont.

Many older calibers used undersized bullets that bumped up or swelled when fired. Many of the Winchester chamberings were like that. In one, I tried the correct size bullet by modern standards, and it wouldnt chamber in the gun, the bullet/case was too fat. The old factory loads generally used very soft bullets that slugged up when fired with black powder loads.


*http://www.midwayusa.com/product/462291/cerrosafe-chamber-casting-alloy-1-2-lb

Very simple and easy to use this stuff. Its reusable also.

 

[orpington]

Anyone else out there have any experience with this cartridge, rifle, or bore diameter?

 

[Don McDowell]

Get ahold of a .530 round ball and see if it will drop into a fired case. That will tell you if you can use a bullet larger than .512. If that works and you don't want to do a chamber cast then, you can start ordering moulds at .520 diameter and going up until you find something that will work.
Best bet is to do as Malamute suggested and do a chamber cast that includes at least an inch of the barrel in front of the chamber.

 

[Jim Watson]

Yours just squeaked by, anything over .5225" was relined when converted from percussion to cartridge. Smaller bores depended on soft bullets upsetting to take the rifling.

I have seen two in action, shot one of them.
A friend has one that is about Minute Of Hostile On Horse, MOHOH.
The other got close to but never hit a BPCR Metallic Silhouette Pig (300 meters.) Probably would have hit that HOH.
So you should be able to hit something as close as 50 yards.

Can you line up a hollowbase .50 mold?

 

[Curator]

When the US Army armorers began to convert the 1859 & 1863 Sharps Linen cartridge breech loaders to the .50-70 cartridge, they checked the "bore" (land) diameter. If that was more than .5225, it was relined to .5215. Anything less than that was simply rechambered and new breech block with firing pin fitted. Apparently your gun was one of the ones that was not re-lined. You might find out if a .50-70 cartridge case will chamber with a "groove-sized" bullet.If not, as others have suggested, a hollow base slug might help, or possibly the use of a ballistic filler like "Pufflon" or the old-fashioned Cream of wheat cereal.

 

[orpington]

It was early in the morning when I posted this...I think.

With land diameter of .522 a .524 bullet would work and these are available.

The groove diameter is indeed .541. However the part about .543 bullet is in error.

Much thanks for the responses! I remember reading long ago the historical information about bore diameters but could not find the source. Sources anyone?

 

[orpington]

If the bore diameter (lands) is .522 and the groove diameter is .541, what would be the ideal bullet size? I know that, for example, a .30-06 has a land diameter of .300 and a groove diameter of .308, so bullets are .308. But, the difference between lands and grooves is only .008, whereas, in my rifle, it is more than twice as much, at .019. In your experience, do 19th Century rifles have deeper grooves relative to lands as compared to more modern rifles? Does it have something to do with black powder?

 

[Malamute]

Don McDowell probably knows a bit about the ins and outs of original guns of that period.

The usual advice on cast bullets is to use a bullet .001"-.002" larger than groove diameter. Type of rifling may have some bearing on that, the old 3 groove rifling* with very wide deep lands and grooves may be able to get away with a smaller than average bullet relative to groove diameter, but I'm guessing about that.

Again, the original bullets were often undersized, and being very soft, would swell up or "bump up" on firing to fit well enough to shoot decently. Most modern bullets are way harder than was common then though.

* Just reread your original post, you mentioned it was 6 groove. The govt springfield barrels were 3 groove.