The 45-70-2 1/10 Sharps
By Chris Peterson for C. Sharps Arms Inc.
The 45-70 Government cartridge was adopted by the United State Military in 1873. The standard service load for the infantry rifle was 70 grains of black powder and a 500 grain bullet. Shortly after this round was accepted by the Army, a second service load was introduced for the carbine. The reason for this second loading was that the issue rifle round recoiled heavily in the light cavalry carbines. This second loading contained 55 grains of black powder and a 405 grain bullet.
Not surprisingly, the Sharps Rifle Co. began chambering their Model 1874 rifles for this round shortly after its introduction. As they did with all the other calibers they offered, they began offering ammunition in this case length for their rifles. They christened their "new" round the 45-70 Sharps. It was also known as the 45-70 Sharps, but it was dimensionally identical to the military round. Sources indicate the Sharps Rifle Company offered a variety of bullets in this caliber, including a 293 grain express, a 400 grain grooved bullet and paper patched bullets in 400, 420, 500 and 550 grains. In fact, there were at least three different designs of 550 grain bullet available. A large amount of ammunition was loaded for the 45-70-400 grooved bullets also.
After the addition of this chambering to the Sharps Rifle line, it gained rapid popularity on the frontier, owing in part to the ready availability of military ammunition. By the time manufacture of the Sharps Rifles ceased, more cartridge rifles had been sold in 45-70 than any other caliber. This popularity continues today in the New Model Sharps rifles.
Much has been written about loading for the 45-70 government. Volumes of loading data are available. But, almost without exception, this information has been developed in rifles of modern design and manufacture, sporting barrels seldom exceeding 24 inches. Also, the vast majoring of the available loading data is for smokeless powder.
Smokeless powder has its place and can be used quite successfully to load ammunition for the Model 1874 Sharps. But, first and foremost, the Sharps is a black powder cartridge rifle. It therefore seems fitting that data using black powder be made available.
Velocity data was obtained using new Sharps rifles with Sharps chamber dimensions. This included the long throat designed to accept paper patch bullets, accounting for cartridge lengths often in excess of recommended maximum from other sources.
All testing was done using CCI-200 primers, GOEX black powder and Winchester cases. All grooved bullets were cast from a Lyman No. 2 alloy made up from pure lead, 50:50 solder and stereotype. The bullet lubricant was commercially available and applied when the bullets were sized. A .457 inch bullet sizing die was used.
Only loads which produced nominal four inch or smaller five shot groups at 100 yards are tabulated. This standard of accuracy was selected because in many cases the rifles being used for testing were equipped with only the standard barrel sights.
As mentioned in one of the introductory articles, the key to acceptable and often exceptional accuracy was controlling the fouling in the barrel. For most of the tests, the best compromise of time and fouling control was either strictly brushing between each shot or blowing down the bore from the breech end and then wiping with a dry patch.
Accuracy with plain base bullet designs was almost always poor to non-existent unless some means of protecting the bullet base was used. For full case capacities of powder, a thin cardboard wad served this purpose. For powder charges slightly less than case capacity, felt wads did the trick.
All loads were measured by volume. Previous testing has shown that minor weight variations of black powder from shot to shot are insignificant. And, indeed, this testing sequence bore that out. Single digit standard deviations for a test lot of ammunition loaded in this manner became the norm.
Full charges (70 grains) of Fg powder would overflow when poured directly into the cartridge case. This necessitated the use of a two-foot drop tube. An alternate method of settling the powder is to set the case of the cartridge on a rapidly vibrating machine while pouring in the powder. A Turbo Tumbler case polisher works beautifully for this. Maximum charges can be settled to provide sufficient case neck for bullet seating and proper powder compression without destruction of the powder granules.
Not all loads were tested in all barrel lengths. Emphasis was placed on those barrel lengths of greatest popularity. Leading the list are the two models of sporting rifles with their 30 inch tapered octagon barrels, followed by the Long Rang Express with its 34 inch barrel. Limited testing was performed with a 28 inch Business rifle for comparison purposes.
One final note. Some shooters prefer plain base bullet designs over thos which accept gas checks. The RCBS 45-500-FN mould used for testing was modified by machining the top of the mould blocks to remove the gas check. This operation shortened the finished bullet slightly and reduced the cast weight to 465 grains. Modified as it was, this bullet performs very well.