Smokeless Propellants: Plentiful Options for Balancing Velocity and Accuracy

I’m too clumsy to have ever been a good skier, so when I say “fresh powder” I’m not talking about the chilly white stuff we hope for on the slopes or the first day of a fall hunt. I mean the powder that comes in cans, jars and kegs. In my world, mostly nitrocellulose-based smokeless propellant. It’s been with us since its invention in France by Paul Vielle in 1884, delivering higher velocity than blackpowder.

Unless contained, smokeless “powder” isn’t really an explosive, although it burns at a very high rate. The expansion of the burning gases pushes the projectile down the barrel. Rate of expansion is generally a bit faster than 5,000 fps. As long as we use nitrocellulose propellant, this puts a practical limit on velocity, but you get all the way there because of friction and force required to push the bullet through the rifling. Somewhere north of 4,000 fps remains the practical limit, still achieved by just a handful of cartridges.

Improvements have included stability, texture and burning rates. After World War II, Bruce Hodgdon created his business from war-surplus propellants. When I started handloading, my initial powder supply was original Hodgdon, decanted from kegs into smoky-glass quart jars. That was not a great way to store powder, but I wish I’d kept some of those jars.

I don’t know how many commercial propellants were on the market 50 years ago, but nothing like the amazing selection available today. New propellants are now coming along so quickly that few lists are complete. My 10th edition Hornady manual lists 147 propellants in order of burning rate from fastest to slowest, many of which I have never seen. Second-fastest is Bullseye, a traditional pistol powder. The slowest-burning powder I’m familiar with on this list is Hodgdon’s Retumbo (fourth slowest), developed for large-cased, overbore-capacity cartridges.

Burning rate doesn’t speak to pressure. That depends on case capacity and design and volume of load. Fast-burning powders are generally pistol and shotgun propellants, used in small doses. Most of my handloading is for centerfire rifles. I have to climb a third up the chart before I see a number I might have on hand: Alliant 2400, No. 46 on this list, developed for the .22 Hornet.

With the many choices, it’s unlikely to know all the suitable propellants for a given rifle cartridge. Sporting rifles being finicky creatures, it’s less likely to initially pick the “best” propellant. Depending on intention, “best” may be greatest accuracy, highest velocity or a compromise between the two. Given variety, cost and availability, it’s unlikely you can try all the options.

It’s good to be exhaustive in experimentation, but figuring out even where to start can be bewildering. For most rifle cartridges, reloading manuals will suggest a selection of “suitable” propellants. These propellants were developed something close to design velocities at specified pressures. With all the choices, different manuals will suggest a slightly different selection of propellants. This shouldn’t be surprising because there is overlap and redundancy in the burning rate chart, with numerous propellants pretty similar in performance.

Manuals will suggest the fastest, and some offer the most accurate propellant for a given cartridge. I find these recommendations useful for starting points, especially with initial loads for an unfamiliar rifle or cartridge. However, accept that this information really only applies to the specific barrel used for the laboratory testing. One size does not fit all.

A better clue can be found in the fact that all loading manuals list burning rates from top to bottom, fastest to slowest. You run into quirky and finicky barrels, so any given propellant may not provide the optimum results in your barrel, but I usually find best accuracy with a propellant somewhere in the middle of the tested options.

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Accuracy is one thing, velocity another. These two often don’t mesh perfectly. Part of the fun with handloading is you can vary the mix of components almost infinitely. For accuracy, bullets are usually the biggest variable. Some are better known for consistently tight groups, but there’s really no predicting exactly what projectile a given rifle barrel will shoot best.

Demanding rifle shooters often achieve measurable improvement by switching brands or intensities of primers. Historically, I’m too lazy for that. Right now primers are the scarcest commodity. Can’t get them even if I wanted to switch around. After bullets, propellants are the easiest components to switch out. Everything is hard to come by right now, but these two also offer the most choices.

I was looking for a good “unleaded” .270 load for my Joe Balickie .270, an accurate rifle I hadn’t loaded for. I had some 130-grain Barnes TSX bullets on hand, and I compared several loading manuals. Some suggested different propellants, but all had in common several medium-slow numbers. Some I had, others not. Using the same bullet, I loaded a series of cartridges with several propellants—avoiding maximum loads, which vary from book to book—using the old routine of “up a half-grain at a time.”

With my dies, I have notes on loads that have worked well in the past. I tried 4350, 4831, RL 17, RL 19 and RL 22. The search could continue, but in this batch and in this rifle, the clear tack-driving winner was stored data from the 1990s for a long-gone .270: 55 grains of RL 19, just okay in velocity but with spectacular accuracy.

My Serengeti .264 shot so well with factory ammo that I’d never worked up a load, but I was running short, so it was time. In 6.5mm, I had Berger, Hornady and Remington AccuTip in the 129- to 130-grain range. Overbore capacity, the belted .264 needs slow-burning powders, which I had on hand. I tried 4831, IMR 7828 SSC and RL 25.

The latter is a relatively new and very slow-burning number that I expected to group the best. Not! Among this batch, best groups were with a plain old Hornady 129-grain InterLock with IMR 7828 SSC (Super Short Cut). With smaller granules that meter well, SSC is another newer propellant I hadn’t used. Interestingly, velocity was also highest at a whopping 3,244 fps.

I won’t quote the charge weight because it was over max in some manuals but not in others. Such variances are common, and there were no pressure signs in my rifle.

The old rule always applies: Start low and work up carefully. I would prefer to use a more modern bullet with better aerodynamics, so my work isn’t done, but this was a happy and unusual coincidence of highest velocity and best accuracy—simply by using “fresh powder.”