Unmasking the Blackpowder “Volumetric Grain” of Doom
Gun manufacturers and powder sellers have been generally ignorant, lackadaisical, and sloppy about referring to “volumetric grains” and volumetric equivalents of blackpowder and blackpowder synthetic replica powders for decades. It is not what you might think, and not only not are there no “universal standards” for volumetric grains, there never were. Yet, some manufacturers dodder on, suggesting that blackpowder is supposed to be measured by volume, or was designed to be. This is absolute rubbish.
You won’t find any definition of a blackpowder volumetric grain from the National Institute of Standards and Technology (NIST), or any other source that I know of. The reason is simple; there is none. Blackpowder has always been measured by weight, not by volume; just like breakfast cereal. You buy blackpowder by the pound, and that is weight, not a “volumetric pound.”
The avoirdupois dram is the unit of weight used to measure black powder. There are 256 drams in a pound avoirdupois, 16 drams in an ounce, and 7000 grains in a pound. 1 gram = 15.432 grains = 0.564 drams. These are all weight measurements, and always have been. Volumetric measuring of blackpowder has never been accurate, and it isn’t today.
A closer look at this mess makes it obvious why volume is not precise. The geometry of blackpowder itself varies by its own granulation size; Fg, FFFg, FFFFg, and so forth. Trying to measure blackpowder (or anything else) by its bulk is tricky. Blackpowder varies all over the place by geometry, moisture content, and even composition percentages. Ian McMurchy published actual weight of 100 gr. volumetric Goex FFg as 101.3 grains, 100 gr. volumetric Goex FFFg as 101.6 grains. (Page 81, Modern Muzzleloading For Today's Whitetails.) Mr. McMurchy didn’t stop there; Pyrodex Select (which is a very large granulation size) weighs in at 63.9 grains, Pyrodex RS at 72.5, Pryrodex P at 73.0, Pyrodex pellets at 74.2, Arco at 94.7, Clean Shot at 85.1, and Quick Shots at 65.5 grains of actual weight. The “Arco” cited is the old “Black Mag 2.”
Not only does volumetric grain have no exact correlation to weight, it has no precise correlation to performance. Ian McMurchy (in the very same book) chronographed 100 volumetric grains of various blackpowders and substitutes through his Oeher 35P pushing a 300 grain bullet, recording 5 shot average velocities from 1233 fps up to 1594 fps all with “100 grains of powder.”
When muzzleloader manufacturers say “100 grains by volume max load” they really are saying nothing that can be accurately quantified. As far as I’m concerned, it is a pretty darn stupid statement—considering that the pressure a powder charge develops has a lot to do with projectile type and weight. A “maximum load” is not a logical thing to proclaim without inclusion of precise projectile weight and type. This starts out dumb, and just gets dumber.
Not only does “by volume” vary all over the place by propellant, the volumetric blackpowder measures themselves are hooked to no particular standard. You cannot buy an SAE, ANSI, CIP, or SAAMI calibrated black powder measure—no such animal exists. The 10 grain (or 5 grain) hash marks on various blackpowder measures (whether made from brass in Red China, India, or in the US from clear plastic) themselves do not agree on what 100 grains by volume is.
The shotgun industry has also has its problems with “drams equivalent.” Many shotgun shells sold today still have “drams equivalent” of blackpowder printed right on their boxes. Somebody, somewhere, decided that a weighed charge of three drams of some brand and some granulation of blackpowder in some 12 gauge shotgun with some type of hull, some type of wad, and an unspecified barrel length, bore size, and choke constriction just happened to propel 1-1/8 ounces of shot at exactly 1200 fps on the nose in front of the muzzle. The scattergun sports industry has been stuck promulgating black powder dram equivalents ever since; an amazing shame.
Nevertheless, the volumetric grain of true blackpowder was “close enough” to the actual weight (within 10% as a generalization); considered more than close enough for field use with such a very inefficient, low yield propellant. It was and is, with true blackpowder.
It is of little help to today’s muzzleloading hunter, who ponders how such crudely made propellants such as American Pioneer / Shockey’s Gold with all the consistency of gravel can be accurately volumetrically measured, and how pellets and sticks can be considered volumetric equivalents to powder when they suck moisture and have clearly visible chunks missing out of them. There must be some type of perpetual motion or circular logic at play here: pellets and substitutes are touted as “volumetric equivalents” to “blackpowder volumetric measures” which are inaccurate, imprecise, and comport to no recognized standards in the first place.
It is currently a triumph of how accurately one can reproduce inaccuracy in measurement. I hope we all wake up soon and decide that words means things, including the word “equivalent” that means "equal to," not “it just might go bang.”
Copyright 2007 by Randy Wakeman. All rights reserved.