May 15, 2020
By Allan Jones
When active in cowboy action matches, my friend Brett Olin, a retired CCI rimfire engineer, shot blackpowder ammo exclusively. He’s quipped that “smokeless propellant is a passing fancy” and had a sign on his shooting cart that read “Smokeless is for Kids!”
Historically, he makes an interesting point. Earliest references to a mechanical mix of fuels and oxidizers date to around 800 AD. This stuff was launching projectiles from tubes by the early 1200s. The final usurpation by smokeless propellants of blackpowder’s dominance in small arms did not finish until after World War I. I’d rate a 700-year service life as remarkable.
There are many forms of blackpowder, depending on its use. Propellant blackpowder intended for small arms is usually the most refined. It has high-grade potassium nitrate oxidizer and carefully prepared softwood charcoal. Although “clean burning” is seldom used in the same sentence as “blackpowder,” quality propellant-grade blackpowders produce less residue than their industrial counterparts made with lower-grade materials.
I have garnered a modest but varied experience with blackpowder firearms; the only class I’ve not tried is a flintlock. It was a blackpowder cartridge rifle that caused me the most grief.
In my youth I had a nice U.S. Model 1873/84 Springfield “Trapdoor” .45-70 rifle. Accuracy was poor, and I didn’t need a chronograph to know the loads were inconsistent. “Off” sounds in the report told a sad tale. I later owned an 1874 Sharps musket in .45-105-550 and found 90+ grains of blackpowder did not improve the situation. Experience in smokeless propellant reloading left me ill-prepared for dealing with a blackpowder cartridge rifle.
As a group, we handloaders had basically forgotten what our forebears learned and applied to the loading of blackpowder cartridges. Interest in cowboy action shooting spurred historical research that changed the way we now manage blackpowder ammunition.
There were some big names—like Paul Matthews, Spencer Wolf, Steve Garbe, and Mike Venturino—among the researchers. Olin found their research very helpful as he honed his considerable skills with blackpowder cartridges.
Olin proposed a ballistics research project on blackpowder cartridges and needed my new (expensive) .45-70 Krieger pressure barrel fitted with a PCB piezo-electric transducer (also expensive). I let him use my equipment.
His study was not intended to create loading data but rather generate statistically sound data on pressure and velocity variations that affect blackpowder internal ballistics. We shot over 1,000 rounds under highly controlled conditions. He chose the CCI Quality Assurance tunnel so we didn’t have to move the plotting gear that creates time-pressure curves to the Speer tunnel a mile down the road. Time pressure (t-p) curves go from the ballistics computer to an X-Y plotter that overlays all shots in a string on one graph. Plots showed commercial blackpowders have a pressure-rise profile very similar to modern smokeless fuels.
The plots also settled a point of contention. For years, I’d heard that magnum primers performed better in blackpowder cartridges. With one exception, the numerical data showed the opposite. Ballistic consistence was better with standard rifle primers. The t-p curves showed even more. One typical 10-shot test with everything identical except for primers showed peak pressure with magnum primers occurred from 410 to 590 microseconds after ignition, but standard primers of the same brand produced a much smaller variation: 420 to 480 microseconds. The plots are reproduced on page 171 of the Speer Reloading Manual #14.
Peak pressures with blackpowder were impressive. Some types of blackpowder exceeded 20,000 psi, about the same as modern .45 ACP ammo pressures. The effects of granulation were far more apparent than any changes in primer type. With all other factors equal, substituting the same volume of the smaller-grained Goex 3F for Goex 2F increased pressures 4,000 psi and pushed the 524-grain bullet 100 fps faster, from 1,050 to 1,150 fps. Yet pressures stayed under 21,000 psi, a number most researchers find appropriate to the 1873 Springfield action.
Today, I understand that my issues with that Trapdoor Springfield were complex. The handsome “glazed” blackpowders were largely missing from the U.S. market from World War II until some was imported from Scotland in the 1980s. Those granules had a rounded appearance from tumbling that produced a clean, silver-gray metallic appearance, and it looked quite similar to modern spherical propellants.
I’ve maintained a modest collection of 19th-century rifle ammo, including Sharps cartridges. I had a sample of UMC .45-105-550 Sharps with a loose bullet and decided to peek inside. Okay, today that single cartridge would probably cost $75 or more, but I was young and curious back then. Under a lube wad the powder had the shiny gray color common to high-grade glazed blackpowder. It was obvious the charge had been compressed to shape—and not by bulletseating. No lead bullet could remain undeformed under the pressure needed to compress that load of blackpowder. Clearly, compression preceded bulletseating.
This was something Olin applied to the tests he conducted. He built a compression die to let a steel punch do the compressing while the case body was supported to prevent its swelling under the force. This seems to be one key to better burning and uniform performance.
Olin’s study showed many factors that could have vastly improved my .45-70 experiences with that old Trapdoor. Of course, in the early 1970s, we did not have the selection of blackpowders we see today, but his approach also helped me understand that I was using overly hard bullets that were undersized and not using enough powder. I could have gotten away with a bit of seating compression, but as I’ve said, back then we approached blackpowder with a smokeless powder mindset.
Brett Olin’s strong competition performance in sanctioned long-range events convinced me that “going back” was in reality a huge step forward in understanding our history and appreciating those who came before us.