Black powder primer: Part 1
This report covers:
- Formula for black powder
- Blasting powder
- The high water mark
- Use by volume
- The deal
- Burn residue
- What’s next?
Several readers said they were interested in learning more about black powder, so today we begin.
The biggest thing to know is this stuff didn’t start out being called black powder. Back at the beginning it was just called gunpowder in the English-speaking world. Although the history is clouded, it seems that some form of this powder may have originated in the Orient, possibly China. And what they had was known there for hundreds of years before the Franciscan Friar, Roger Bacon, wrote down the formula in 1267. He wrote that a “toy” no bigger than a child’s thumb could produce fire and sound from a mixture of saltpeter, sulphur and willow bark charcoal. He was describing a firecracker.
Formula for black powder
While this formula evolved over many centuries, it is today regarded as 75 percent saltpeter (potassium nitrate), 15 percent charcoal (specific types of charcoal will change the power of the powder) and 10 percent sulphur. The saltpeter is the oxidizer and the charcoal and sulphur are the fuel.
Each ingredient is important to the outcome. Not just the purity of the ingredients, but where they come from matters to the greatest degree. Each ingredient must be broken down to as fine a powder as possible — separately, of course! Then they are combined in boiling liquids, squeezed into a ball, air-dried (but not completely dry) rolled out into a flat sheet, then cut, pressed or divided into grains and allowed to dry completely. Once dry those grains are carefully ground into a fine powder, and the size of the granules of powder determines the rate of burning. A gross simplification says that when confined so pressure is allowed to build, black powder burns at the rate of 11,000 feet per second. It is considered a low explosive.
By changing the ratio of the ingredients, a powder called blasting powder can be made. In simple terms it has less nitrate and more charcoal. Sodium nitrate is usually substituted for potassium nitrate. Blasting powder creates a more violent shock when it explodes. So, to remove a stump from the ground, where a heaving force is needed, black powder is best. When you want to shatter rock, such as in a coal mine, blasting powder works best.
The high water mark
Black powder became the focus of extreme interest around 1730, when the American flintlock that we know today as the Kentucky rifle began its evolution. Instead of pouring a hundred grains of powder into a large-caliber European Jaeger rifle, the Kentucky got by with 40 grains or so. When that occurred the quality of the powder started being closely noticed. English powder was the best by far, and one or two brands stood out from the rest. People paid more for those brands because of their known quality.
Black powder began an evolutionary improvement cycle that peaked near the end of the 19th century, just as smokeless powder was coming into being. The black powder we have today isn’t up to the same standards as that stuff that was sold back in 1880. But even so, some brands are still better than others. The Swiss brand is generally considered the best today, and GOEX is another fine brand.
Use by volume
I’m now skipping past centuries of development and refinement. The firearm (gun) that we know today was invented in the very late 1200s. Gunpowder was still in its infancy (remember Bacon and the year 1267), so a lot more was used to get results. Guns were not aimed back then, they were pointed. And they launched multiple projectiles — not the uniform shot we know of today, but rocks, pieces of iron and anything that would do damage when it hit at high velocity.
How much gunpowder was used was a best guess during those times. They just poured it in and hoped for the best. The metallurgy was also slipshod in those days and guns did blow up. That was considered a hazard of shooting.
So, using gunpowder (now meaning black powder) started out by volume and not by weight. And it remains so to this very day. Can you use too much? Definitely. Will black powder guns still blow up? Absolutely. Perhaps you veteran readers remember back in 2013 when BB blew up his Nelson Lewis combination gun (read Part 4 of the Nelson Lewis combination gun report). The entire gun didn’t explode, it just blew out the nipple, but that was close enough for me! As it turns out that same thing has happened to a number of people, so it’s not just me.
But here is the important thing — the deal. The power of modern black powder is so uniform and incremental you have to be reckless (as I was) to have problems. There isn’t much difference between using 21 and 24 grains of powder, as long as the gun is sound. So we fill a calibrated powder measure (calibrated to the gun in use) and then dump the powder into the gun. As long as our actions to fill the powder measure remain the same every time (for example not packing it in or filling it to heaping) the measurements are usually within a grain or two. And with black powder, differences that small don’t matter.
This is an animal bone powder measure for my .61-caliber flintlock fowler. Filled to the brim it holds about 60 grains of FFG powder.
With cap and ball revolvers it’s even simpler. You can’t fill each chamber too full because a ball has to be rammed down on top of the powder, and then the top of the ball has to clear the end of the barrel so the cylinder will revolve. Remember the problems I had with the RMAC rifle?
For those reasons, we don’t weigh black powder charges; we use powder measures. Even for the larger caliber rifle cartridges, the method remains the same. Our powder measures for the large cartridges are also volumetric rather than weight-oriented.
And there are some other things we can do to make the powder fill more consistent. Like dropping the powder charge down a long tube so it packs itself into the cartridge with consistent density at the end of the fall. That tube is called a drop tube and most cartridge reloaders who work with black powder use one.
A drop tube is a simple way of concentrating black powder in a cartridge the same way every time.
When today’s black powder ignites, about 45 percent turns into energy and 55 percent turns into residue. Smoke is the greatest residue, followed by ash and soot. Shooters have to find creative ways of removing that ash and soot, as it is hygroscopic and starts attracting moisture and rusting the gun immediately.
In ancient times about 60 percent of powder turned to residue. That reflects the lower power of the powder up to the 18th century.
I haven’t mentioned that black powder doesn’t have to be black. It can be gold, white and even pink. It also doesn’t have to smoke much or smell bad. It can even be formulated to clean the bore.
I haven’t addressed the fineness of the powder. That’s where the F designation comes in.
I have been talking about gun powder. There is also cannon powder to consider.
This is a huge subject. We are just going to touch on it, because we are airgunners. Still, things like bore obturation, and the rate of rifling twist to the stability of the projectile remain the same. And with black powder we remain at velocities that are very similar to airguns.