Measuring Black Powder Loads
Black powder loads are expressed in a measurement called grains. Grains are a unit of weight, but black powder is loaded by volume.
This is a subject that can be confusing.
On internet discussion boards, I’ve seen people post a load, of a certain ball, and so many grains of black power, only to have people ask, “Are you talking grains of weight, or grains of volume?”
A lot of people think that “grains” work like “ounces”. We all know that the term “ounces” can refer to either weight, where 16 ounces equals one pound, or volume, where 16 ounces equals one pint. Same name, “ounces”, but vastly different types of measure.
Grains are not like ounces. Grains are strictly a measure of weight, not of volume. Grains are probably the earliest unit of measure still in use. Recorded use goes back to the Sumerians 5,000 years ago. Nominally, a “grain” is the weight of a grain of wheat. Technically there are 7,000 grains per pound.
All ballistic powder charges, whether they are loaded using black powder, or modern smokeless powder are expressed in grains. So, if you read that a hunting load for a .50 caliber rifle is a patched .490-inch round ball over 90-grains of 2Fg Goex black powder, that means the powder charge weighs 90 grains.
Realistically though, almost no one, except precision target shooters, weighs out each charge of powder. That’s where things can get confusing. All powder charges are expressed as a weight, but most powder charges are dispensed by volume.
This is true for both smokeless and black powder. Smokeless powder reloaders use a powder measure like RCBS’ Uniflow measure. The Uniflow has a powder reservoir that fills a powder chamber that holds an individual powder charge. The volume of that chamber is adjustable. So, if a reloader needs to fill a .38 Spl case with 3.6 grains of Bullseye powder, he would adjust the charge chamber and throw a powder charge, which he then weighs on a scale. If the load is light, he will adjust the Uniflow to make the powder chamber bigger, and he’ll throw another load, and check it again on a scale. The reloader will adjust the chamber, and weigh again, and will repeat that process until the Uniflow Powder Measure is consistently throwing a charge that weighs 3.6 grains. Then he’s ready to start reloading. During the reloading process, he is loading the volume of Bullseye being dumped by the Uniflow.
With black powder the process is the same, except we usually use powder measures that are pre-calibrated for a certain weight of powder…more or less. The typical brass, black powder measures on the market today consist of a cylinder with a sliding piston that changes the volume of the cylinder as it slides up or down. The pistons are generally marked in 10-grain increments.
So, if you set the measure to the 30 mark, it should throw a powder charge that would weigh 30 grains if you dropped it on a scale. I say, “should throw”, because the people who made that powder measure have no idea if you are going to shoot 2Fg powder or 3Fg powder. They don’t know if you are going to shoot Goex brand black powder, or Swiss brand black powder. If your powder measure is calibrated for 2Fg Goex, the 30-grain setting will probably actually throw 32 or 33 grains of 3Fg Swiss powder.
If we were loading with smokeless powder, a three-grain difference might be enough to blow up your gun, but black powder is much more forgiving. Which makes those pre-calibrated powder measures safe and easy to use.
That’s a good thing, because weighing every charge would take a lot of the fun out of shooting.
The really important thing with a black powder measure, whether it is an adjustable brass measure, or a measure whittled out of an antler tip, is that it be consistent.
That will usually depend as much on your filling technique as on anything else. Personally, I prefer to fill a measure so it is a bit heaped over the brim, and tap it with a finger to level it. What ever your technique is, do it the same way each time. If you do that, you should get consistent results, shot to shot.