Smokeless Powders Lose Temperature
Sensitivity, Part 2
By John Barsness
The quarter-century after World War II saw the biggest economic boom in US history. Among the by-products were a lot of new toys for American shooters, who increased in number and often started handloading. Before the war, handloading was often seen as a peculiar if not downright dangerous activity, but when I started handloading in the mid-1960’s at the advanced age of 13, several of my father’s friends provided advice.
Local stores had plenty of cheap powder, much of it repackaged “war-surplus” originally purchased by the boxcar by Bruce Hodgdon, and commercial powder manufacturers had to compete with Hodgdon’s prices. My first can, a pound of IMR3031, cost $1.95, and several Hodgdon powders cost slightly less. (I bought IMR3031 because it was listed for the scoop powder measure of the 7.62 Russian Lee Loader for my war-surplus Mosin-Nagant.) Adjusted for inflation, $1.95 amounts to about $14 in 2016, about half the average retail price today.
Powders had improved considerably just before the war, becoming cleaner-burning and less temperature sensitive. They were also far more stable during long-term storage, one reason Hodgdon’s supply of the 20mm cannon powder he renamed H4831was sold until the mid-1970’s—and some is still in fine shape. In 2015, I popped the lid on a cardboard canister of mil-surp H4831, and it worked in my present .270 Winchester, just like it did in my first .270 back in 1974.
No wonder many post-war handloaders thought rifle powders had been perfected, but several new developments led to some wanting more. By the 1970’s chronographs appeared serious handloaders could afford. For some, handloading became a competition over who could come closest to turning their .30-06 into a .300 magnum, thanks in part to new and zippier double-based powders.
In the 1990’s even cheaper chronographs appeared, along with laser rangefinders. Many handloaders naturally started stretching how far they’d shoot, in the process discovering velocities from many of the new super-zippy powders changed considerably at different temperatures. This basic ballistic fact had long been known to target shooters, who loaded slightly different charges for varying conditions, or clicked their sights or scopes to compensate, but most hunters hadn’t noticed the difference, because most didn’t shoot at distances where varying velocities mattered.
Laser rangefinders changed all that, and many shooters started yearning for more temperature-resistant powders. The first to appear were Hodgdon’s Extreme powders, made in Australia, including the third version of H4831. When the mil-surp stuff ran out in the 1970’s Hodgdon had a replacement made in Scotland, but the Australian stuff not only came closer to matching the pressures and velocities of the original H4831, it proved far more resistant to temperature.
At this point we need to define temperature resistance. Almost any smokeless rifle powders can be fairly temp-resistant in one or two cartridges with certain bullet weights but velocities will vary more in other cartridges. Hodgdon’s Extremes widened the range of temp-resistant cartridge/bullet combinations for each powder.
In 1990, after buying a house with enough land for a personal shooting range (making testing convenient whether in the biting cold of a Montana winter or the heat of summer), I started testing powders in varying temperatures. For many years, the rule-of-thumb had been a gain or loss of about 2 feet-per-second for every degree Fahrenheit. In fact, this was even suggested by a chart in my very first loading manual, the Speer No. 6.
“Greenhousing” ammo inside a clear bag placed in the sun can
increase its temperature substantially even on 100-degree days.
Testing loads in actual cold, with both the rifle and ammo chilled, is more
informative than just chilling the ammo. This Montana morning was right
around zero Fahrenheit.
Most temp-tests are performed with the ammunition chilled or heated, but my seasonal tests were made with both the rifle and ammo at the same temperature. This made a considerable difference, not just in velocity but point-of-impact. In one of my first tests in real cold, the POI of a popular handload in a .270 Winchester shifted 3 inches at 100 yards. Since then I’ve only seen that much change once, but shifts of 1 to 2 inches are common and happen mostly in rifles where a slight change in powder charge will also affect POI.
Until the appearance of Hodgdon’s Extremes, I’d found the 2-fps/degree rule fairly accurate. Many powders lost around 100 to 150 fps from 70 to zero, though they gained somewhat more velocity per degree above 70. The Extremes, however, normally didn’t lose significant velocity from 70 to zero. A load with H4831 in the .338 Winchester Magnum and 250-grain bullets lost an average of 13 fps, and a 7×57 load with H4350 lost only 8 fps. Although, some older powders could be pretty good in specific applications. Good old IMR4350, introduced in 1940, only lost 38 fps in a 300-grain .375 H&H handload, but lost 74 fps in a 165-grain .30-06 load.
Soon more powders touted as temperature-resistant appeared, even some spherical powders, generally considered more sensitive than extruded powders. In 2000, I was invited by a distribution company named Western Powders to try some new spherical powders they’d imported from Belgium. The first of these “Ramshot” rifle powders had been developed specifically for the 5.56×45 NATO, so theoretically would work well in the .223 Remington. Called TAC, it got exactly the same velocity at zero as at 70 in a .223 load with 50-grain bullets, and a somewhat slower-burning powder called Big Game only lost 21 fps in a 150-grain .30-06 load.
A couple years later, I tested some Alliant Reloder 15 with 200-grain bullets in the .338 Winchester Magnum, and it proved to be very accurate—but also very temperature-sensitive. I contacted Alliant’s marketing guy, who said, by coincidence, the formula for RL-15 had recently been changed, due to consideration by the US military. He sent a sample of the new “mil-spec” version, and it only lost 36 fps from 70 to zero in the same load.
Since then, new temperature-resistant powders have appeared just about every year, and many older powders are noticeably more resistant, due to manufacturing changes. Of course, many handloaders won’t notice any difference, because they don’t live where temperatures vary as much as Montana, and just about any powder works fine at temperatures from 30 to 90 degrees.
Powder manufacturers are understandably tight-lipped about how they make powders more temp-resistant, though one guy did let it slip that flattening the granules of spherical powders helps. But it doesn’t really matter how resistance is accomplished. The technology is spreading, along with demand.
Other improvements have taken place. The Ramshot rifle powders also burned far more cleanly than any other spherical powders I’d tried, apparently because their resistant coatings burn up when pressure nears maximum. Today, many other spherical powders also burn more cleanly than they used to.
Plus, more companies now add de-coppering agents to new powders. Since both de-coppering agents and cleaner-burning spherical powders were developed primarily to keep military rifles shooting accurately longer, we can probably assume both features are appearing in civilian canister powders due to more shooters buying AR-15’s and other semi-autos.
Many shooters still compulsively clean rifle barrels every few dozen rounds, because that’s what they learned to do years ago. Personally, I’ve always found shooting rifles far more enjoyable than cleaning them! Many 21st-century powders allow us to shoot far more and clean far less, and shoot more accurately in a wider range of temperatures.
Half of John Barsness’s dozen books are on firearms and shooting. His latest is The Hunter’s Guide to Handloading Smokeless Rifle Cartridges, published in the fall of 2015 by Deep Creek Press. It’s available through www.riflesanrecipes.com, P.O. Box 579, Townsend, MT 59644, (406) 521-0273.
P.O. Box 6
Radford, VA 24143
Hodgdon Powder Company, (IMR, Winchester)
6430 Vista Drive
Shawnee, KS 66218
Western Powders, Inc., (Ramshot, Accurate)
P.O. Box 158
Miles City, MT 59301