Semisane

In a thread on another forum one of the members had a powder flask with a 30 grain spout that threw a charge that filled his adjustable powder measure to the 35 grain mark. He was wondering which one was correct. His question generated a lot of discussion that made it pretty clear the "volume equivalent" thing is not well understood by many shooters.

So I thought I would copy part of my response to that thread here just to kick off more discussion. Here it is:

There simply is no standard for volume measures. Get five different measures from five different manufactures and each will throw a different volume of powder. Which one is correct? All of them, and none of them. Remember, all of this "volume equivalent" business is theoretically based on the weight of black powder.

So let's make up a little story.

In the mid-1800's Charlie Wingshooter went to the local gunmaker to pick up his new gun, and bought two pounds of "FF Grade" black powder. He paid $1.60 per pound for that powder because black powder was sold and measured by weight.

So Charlie worked up a load for his new .40 caliber rifle and found a certain amount that shot best in his gun. He took a piece of river cane and cut it off so that it held exactly that amount and tied the measure to his powder horn. Now old Charlie was wondering how many shots he was going to get out of his powder purchase. So the next time he was in town he stopped in at the local apothecary with his powder horn and asked his buddy Abe, the pharmacist, to weigh his charge.

Abe filled Charlie's measure with Charlie's powder, dumped it on the scale and said "it weighs 50.3 grains, but let's try again". The second charge Abe weighed was 49.8 grains, and the third charge was 50.1 grains. So Abe says "Charlie, you've got yourself a 50 grain measure. Now there are 7,000 grains in a pound, so you're going to get about 140 shots per pound of powder". Charlie is happy as a coon in a corncrib, and uses his knife to scratch "50 Gr" on the side of his river cane measure. Is it an accurate and true 50 grain measure? It sure is - for Charlie's powder (because it's based on the actual weight of Charlie's powder, and 50 grains volume = 50 grains weight).

Now let's suppose that last week you bought an old wood chest at an auction and when you got the rusty latch opened at home found it contained a nicely made powder horn with a river cane measure attached to the stiff leather strap. The side of the measure is crudely marked "50 Gr". Out of curiosity you fill it with GOEX FFg and weigh the charge. It weighs 58 grains. Why? Because it's not the same powder the measure was made for. However, the GOEX charge is the "volume equivalent" of Charlie's 50 grain load. You fill the measure with Triple Seven FFG and that load weighs 45 grains, and it too is the volume equivalent of Charlie's 50 grain load. As the manufacturer of that measure, Charlie established the base level for what volume produces a load that weighs 50 grains of the black powder he used as a base level.

Today, as in Charlie's day, there are no standards for "volume equivalent". We are all using approximations based on whatever the manufacturer of the measure thinks is appropriate.