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I've heard people talk about "loading up the 8x56R to 8mm Mauser velocities." After all, they opine, it's an 8mm and it's a military high power rifle cartridge, right? Well, not exactly.
The 8x56R military designation was M30 in Austria and 31M in Hungary, after their years of adoption. That would make it seem that they were a later development than the 8mm (actually, 7.92mm) Mauser, also called 8x57 Mauser. This might seem so because the 8mm Mauser started out around 1898. Those numbers don't tell the whole story. The 8mm Mauser was an original design. The 8x56R was a compromise cartridge designed to update an obsolete Austrian design, the original 8x50R. The 8x56R was used to save money, not because it was a superior design to the 8mm Mauser. The chambers of the many M95 Austrian rifles on hand between the wars were adaptable to being reamed out to a longer profile, allowing a larger case and powder charge. A change to a more modern spitzer bullet of lighter weight also updated the cartridge. The updated version retained the rimmed design and the fat, bulbous case body.
The Austrian and Hungarian defense establishments would probably have liked to change to a completely different weapon and cartridge when they adopted the 8x56R. Money being tight as it often is, they chose instead to hang onto the M95 rifles a little longer since they were already paid for. In fact, Austria had plans to change over to 7mm Mauser as a service cartridge around 1914, but a little thing came up called the Great War and they decided not to complicate matters by changing over their infantry rifles at the same time. Sometimes countries get into wars that last longer than they anticipated (like Iraq??), and if the Austrians had known that the Great War was going to last almost four and a half years, they might have made the change to the Model 1914 Mauser in 7mm. Wouldn't it have been nice if they had made millions of those instead of the M95?? Hungary must have learned their lesson; they did change calibers in the middle of a war, almost 30 years later. In 1943, they changed from 8x56R to 8mm Mauser.
The 8x56R is not as efficient of a cartridge as the 8mm Mauser. I'm not a ballistician or engineer, but anyone can look at the profile of the case of an 8x56R and compare it to the 8mm Mauser. The 8x56R is more bulbous, and even with a slightly larger bore diameter, the burning propellant gases cannot get out of there as quickly as the 8mm Mauser.
As near as I can compile them, here are the comparative statistics on the two military service cartridges:
8x56R - 8mm Mauser
Muzzle velocity - 2,380 - 2,500
pressure - 39,500 - 42-44,000
bullet weights - 208 - 197
charge weights - 55 gr. - 47 gr.
So, we can see that the 8x56R uses more powder to achieve less velocity, admittedly with a slightly heavier bullet. The greater powder charge might explain the nice rap of recoil that so many shooters remark about with the M95 carbines (not to mention the fact that they weigh less than a typical 98 Mauser).
I decided to do my own little test on these two cartridges, using the same weight of bullet and same type and weight of powder. Here are my results
Propellant used: Hodgdon Varget
Charge weight: 44.0 grains
Primers: WW standard large rifle
Graf cases used for 8x56R; RP cases used for 8mm Mauser
Buffalo Arms 175 gr. Spitzer bullet used for 8x56R
Speer 175 g. Spitzer bullet used for 8mm Mauser
Chrono results:
8x56R - 8mm Mauser
Muzzle velocity 2,040 - 2,341
Standard deviation 45.89 - 16.43
So, the above shows that with the same powder charge and same weight bullet, the 8x56R performance is well behind the 8mm Mauser. Of course, this is only one experiment with only one set of components used, but I think it tells a story.
For the record, while Varget is a good propellant for the 8mm Mauser, I don't know that it's the best for the 8x56R. Varget is not the slowest powder available by any means; it's near to IMR 4895. However, my best accuracy results with 8x56R have been with slower stick powders. The problem with them is you can't get enough in the case to get the velocity up. The original factory loads use a European cut sheet powder, which compacts into the case better than extruded (stick) powders. A slow version of this would get the velocities up, but you'd be back to a cartridge with hefty recoil.
Ball powders would fill the case more fully, but I haven't had good accuracy results using them.
My best overall (velocity and accuracy combined) results with handloading 8x56R have come about from the use of IMR 4895.
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