The shooter and handloader is blessed with the widest choice ever of smokeless propellants, commonly called "gunpowder", a misnomer. Gunpowder is that smelly stuff that muzzleloaders stuff down the barrels of those big ol' smokepoles. Commonly called black powder this stuff is a mixture of saltpeter, charcoal and sulfur and is beyond the scope of this particular piece, except to note that for hundreds of years it was all we had.
Black powder has many limitations, it's not particularly efficient in that it doesn't impart a whole lot of power to a bullet, it's messy to work with, it's somewhat dangerous and it leaves a whole bunch of residue behind. The billowing clouds of white smoke were a real drawback in military use. My great grandfathers would be bemused by the resurgence in popularity of black powder.
Smokeless propellants came about, like many of today's conveniences, through military research. The first breakthrough was the discovery that ordinary cellulose in cotton or wood could be soaked in nitric acid to form guncotton in 1845. Guncotton is useless as a propellant as it is impossible to control the burning rate.
Oddly it was a French chemist, a man named Vielle, who made modern smokeless powder possible. He discovered that by soaking guncotton in alcohol and ether one could form it in sheets. Cutting up those sheets into small granules gave us the first smokeless powder. The race was on.
The first cartridge using smokeless was, I believe, a French military cartridge, the 8 mm. Lebel.
Across the Channel the Brits learned that by taking this soft, doughy mixture of wet guncotton and forcing it through a sieve-like apparatus they could make it into a bunch of spaghetti-like strands called "Cordite". It was some decades before they learned to cut up those strands. Initially the Brit ammunition manufacturers simply bundled up a bunch of these cords, shoved them into a cartridge case, then formed the neck of the charged case and inserted the bullet. This wasn't the safest operation in the world. I'm told that the early Brit handloaders were a sight to behold, trying to stick those long cords, one or two at a time, down the neck of a cartridge. All in all, people were extremely relieved when the Brits figured out the concept of cutting those cords up into little pieces.
A factoid about Cordite that some may find interesting is that a large amount of ammonia was used in it's manufacture, along with other chemicals, that gave it a strong, peculiar and unpleasant smell when the cartridges were fired. This gave rise to the term "the stench of Cordite", a term that is still used today by the ignorant. It's been a VERY long time since Cordite was used, the smell of today's propellants is nothing like that. When I was a boy I fired some surplus .303 Brit ammo loaded with Cordite, I know the difference. That ammo was old then, today it would be valuable as a collector's item.
Modern smokeless powder is of two basic types. Single-based powders are made of nitrocellulose. Double-based powders are made of nitrocellulose and nitroglycerine. Each of these types also contain smaller amounts of other chemicals and each is coated in graphite during the manufacturing process. The graphite makes it much easier and safer to work with as it cuts down on static electricity. It's also why smokeless powder is dark gray to black in color. Before the graphite is added the powders are a pale, greenish yellow. A Company in Finland actually makes a powder with yet another ingredient, besides nitrocellulose and nitroglycerine, making it a triple-based powder. The company is Vhita Vouri and the name of the third ingredient escapes me at the moment and I can't seem to get on their website. It will come to me, probably in the middle of some night next week. I'll wake up, shout the name, scare Hell out of the dog, he'll start barking, waking Linda Lou and I'll be in trouble again. Anyhow there are only three of these triple-based powders and I'll pretty much ignore them except to note that they give a velocity boost of some 50-150 feet per second over conventional propellants, at equal pressures.
Besides being classified as to whether they're single, double or triple based, powders are further classified by their kernel structure. By the way, do not refer to each individual speck of powder as a grain. When shooters and handloaders use the word grain, we're referring to a unit of weight. A grain is one seven thousandths of a pound. There are 437.5 grains in an aviorduppois ounce and for those who think in metric, 15.43 grains per gram. Those little bitty pieces of powder can also be called granules.
Back to the classification, powders can be like little bitty sticks, they can be little bitty spheres or flakes and there are some European powders that are formed in big, thin sheets and then die-cut into squares or diamond shapes. The Alcan Powders for shotgun and handgun cartridges were sheet powders, they've been gone for years but they were good stuff. So we call it stick powder, ball powder or flake powder. We Americans don't call sheet powder anything because we never see it.
Stick type powder is quite interesting as it's made like a hollow tube. Each kernel has one or more perforations through it. This is how the burning rate is controlled, by the size of the kernel and the perforation. The spherical or ball powder has it's burning rate controlled by coating each kernel with a chemical that retards burning. Flake-type powders control their burning rate through the chemical composition and granule size. I got to see cannon powder when I wore Uncle's suit, each kernel was big enough to see the perforations.
Smokeless powder is not an explosive, at least in the quantities that even avid shooters keep around not even a particularly dangerous flammable. It doesn't evaporate into a flammable vapor and takes a pretty good spark to light. Unconfined it doesn't even burn very fast. The late General Julian Hatcher, one of the giants of early to mid 20th Century cartridge development, tried to make canisters of smokeless powder explode by shooting into them. It took shooting into a two hundred pound keg before he got anything resembling an explosion, the one and eight pound canisters won't.
The last way we classify powder is by it's burning rate. The way it works is that the powders that are right for loading handgun cartridges are not good for loading full-charge rifle cartridges. There are more than 150 different kinds of powder more or less readily available to the handloader today, each with it's range of uses.
Each one of these powders will not burn efficiently below a given pressure and each becomes quite dangerous when it exceeds a higher given pressure. Generally speaking, the slower the powder, the higher the pressure has to be before it burns efficiently. Another generality...Single based powders USUALLY have a wider range of pressures where they work well than double based powders and they are somewhat more predictable as they approach to upper margin. The short answer as to why is that kernel size stays the same and that's what control's the burning rate in single based powders. In the confined area of a cartridge as the pressure builds, so does the heat, the deterrent coatings that control the burning rate of the double-based ball powders works less well the higher the pressure. That's a very simplified statement as that's the way these coatings are designed to work. Otherwise cartridges would fizzle.
There is no "best" powder. There are usually one or two powders that work best in a particular cartridge in a specific range of bullet weights. That's assuming "best" means highest velocity at safe pressures. We aren't always looking for the highest velocity. The velocity minded handloader can find the powder that delivers for her, or his, cartridge by checking several loading manuals. One or two powders will almost always stand out. Given a choice I always try to go with the powder that gives a mildly compressed load. Why? A compressed load means there isn't enough room in the case to put enough powder in to cause a KABOOM. I like that. I like it a lot.
These days I don't fool with trying to get every last foot-second much. I don't have the wheels for long-ranged hunting, nor, with this Parkinson's, would it be fair to the game to try potting it 'way past Fort Mudge'. So, what little hunting I do is in country where the terrain and cover is such that fifty or a hundred yards is a long poke. At those ranges I don't want high velocity. All high velocity does at close range is waste meat and add noise and recoil. By picking the right powder and bullet I can turn a .30-06, or even one of the .300 Mags, into a .30-30 or .300 Savage. In the words of the late, and sorely missed, Elmer Keith "you can eat right up to the bullet hole".
Handloaders who would like to introduce new shooters to centerfire rifle shooting should be aware of Hodgdon Powder Company's H4895 and the Sixty Percent Rule. Any cartridge for which there is data for H4895 can be loaded at 60% of the maximum load for a load that has far less recoil and muzzle blast than full charge ammo. Then gradually increase the load. These are also wonderful loads for a kid just learning to hunt. They're no kind of squib load. The Sixty Percent Rule will, when used in my .30-06, push Hornaday's excellent 130 grain Single Shot Pistol bullet out at over 2500 fps. Hairy-chested he-men drop deer and even elk with those ballistics and their Thompson Contenders, it'd be just the load for a teenaged daughter.
I talked about the wide array of powders available. I believe the choices are about to contract somewhat. Over the last couple of months there have been some buyouts and mergers. Accurate Powders have been bought by the Western Powder Company, the folks who distribute the Ramshot Powders. And the Hodgdon Powder Company bought IMR. Since many of IMR and Hodgdon's powders are so close together that starting load data can be safely swapped I can see the elimination of near-duplicates. We don't need IMR4895 and H4895, nor H4350 and IMR4350. Hodgdon's Varget and IMR's 4064 are so close together that I've switched according to what was on sale and not had to adjust my scope sight when going from one batch of cartridges to the other.
Will the elimination of the duplication of effort lead to lower prices? I can hope. I'm not holding my breath, though.
Powder is expensive and, depending on the locality, there are limits to how much a private citizen can have on hand without building special storage facilities. The most common amount allowed is twenty pounds. That seems like a lot, it isn't really. A shooter with an autoloading pistol and a magnum revolver, plus just one .30-30 and one high-intensity rifle will go over that limit with a fresh eight pound jug of just one powder per cartridge and what handloader is satisfied with just one powder per cartridge? A quick count in my powder "magazine" shows some twenty-one different smokeless powders, some with more than one jug. Add the only real explosive powders, the canister of FFG Black and that jug of Pyrodex that isn't quite smokeless and isn't quite black. Of course I tend to enjoy experimentation. That's one of the nice things about living in the country. I asked my county Fire Marshall about the specs when I built my magazine. He told me not to put a fireplace in it. I love living in the country. My homeowner's insurance agent was somewhat more picky. Two layers of one inch plywood, covered by twenty gauge steel was the request and please make it lockable. It ain't very pretty, it's just a big box with shelves in it. And a padlock. My insurance agent is happy. If I were doing it again I'd just use a junk refrigerator and put a hasp on it. The insulation on even an old fridge is such that either the fire gets put out or the house would burn down before the powder caught.
When thinking powder safety remember, the fire won't start in the powder unless you do something like looking at the level in the jug by holding a match in there. The whole idea is to try to keep it from adding to a fire that started elsewhere. A thick box, an old refrigerator, even those fire-resistant filing cabinets, any of those will either keep the powder from adding to the fire or the powder won't matter because the house is history anyway.
The most important parts of powder safety have nothing to do with fire. Never mix two or more different kinds of powder. Never have more than one jug of powder on the loading bench at one time. At the beginning of a loading session write the name of the powder you're using down. In big letters. Then look twice to make sure you're putting right powder in the measure and putting the leftover powder back in the right jug. Inadvertently putting pistol or shotgun powder in the measure that's set for your 7mm Remington Magnum is a guaranteed KABOOM.
Smokeless powder when mixed with a little common sense and a willingness to follow the recipe is safe to have around. Far safer than that can of lawn mower gas in the garage. So, for safety's sake, handload, don't mow.