Every precision shooter wants consistency, but powder temperature sensitivity can introduce a variable that many overlook. As outside air temperatures rise or fall, a powder’s burn rate changes, altering muzzle velocity and shifting a bullet’s point of impact. Some powders are less affected by swings in temperature than others, but many introduce enough variation to cause a miss – especially at extended distances.
This article will dive into:
- Advice from ballisticians and industry experts on powder temperature sensitivity
- Quantify what that means in the real world
- Share first-hand test results of the most popular powders
- Itemize a list of some of the most temperature-stable rifle powders
My last article shared load development tips from Jeff Siewert, a ballistic engineer with 40 years of industry experience. Jeff explained that the specific powder we choose has a direct impact on the size of our groups. Some powders are much better than others in terms of maximizing the precision of your rifle.
Jeff’s last point when it came to choosing the optimal powder for extreme precision was this: “The propellant has a low temperature coefficient; its performance is not overly sensitive to increases or decreases in ambient temperature.”
All powders will change to some degree based on the ambient temperature of the powder, but some are far more sensitive than others.
“As a long-range shooter and precision rifle competitor, temperature sensitivity is something we all need to be knowledgeable of and at varying degrees concerned with. There are instances you can get away with a lot of things and not have any concern, not even knowing it exists, but there are also times when, if you don’t account for it, you start stretching the legs on what you’re shooting you’re going to miss the target simply because of the temperature sensitivity of the propellant.” – Seth Swerczek, Hornady Marketing Communications Manager
Handloader Magazine published this powder temperature sensitivity chart, which shows what they’ve measured over the years in terms of variance in velocity with the same load at different temperatures. For one load, they found an increase of 87 fps from the load being at 70° to 115° F! That is an increase of 1.9 fps per degree change!
Let’s say a match started at 40° F and climbed to 80° by afternoon (common in west Texas, where I live). We’ll use the 1.9 fps per degree difference that Handloader Magazine reported. Let’s say our muzzle velocity started at 2800 fps on Stage 1, but as the temperature rose to 80°, our MV climbed to 2876 by the last stage. If our elevation adjustment on a target at 1000 yards was perfectly centered when we started – we’d be hitting over 20” higher by the time we finished! We aren’t shooting 4-foot-tall targets in matches, so you could see how even a fraction of that temperature sensitivity could put you off the plate. In fact, it would only take a 37 fps increase over that 40-degree swing, and it would likely cause us to miss a 20” tall target at 1000 yards.
The example above assumes that everything else was perfect! You broke the shot perfectly, the range was 100% accurate, your ballistic solution was 100% accurate, your wind call was perfect, and your bullet went perfectly into the center of your group (plus lots of other things). If any of those things were off, we could end up off the plate with even less velocity change.
While we’d love to have absolutely no variation in our velocity, it seems like the practical goal for long-range shooters is that we need the variation to be less than 1 fps per degree Fahrenheit. How far under 1.0 you desire will vary from one person to another and based on the application – but we can probably all agree that 1.0 fps per degree or more is too much for precision long-range shooting.
Keep in mind that the outside temperature doesn’t have to be 115° for your ammo to reach 115°. If you leave your ammo in the sun on top of a dark surface, the ambient temperature of the powder inside the case can get there pretty quickly. After all, we aren’t talking about the ambient air temperature but the temperature of the gunpowder itself at the moment of ignition. That is often related to ambient outside air temperature, but not always.
A few months ago, Hornady published a 1-hour podcast focused on powder temperature sensitivity. Their hopes were to make it easier to understand, calculate, and account for. I will share a few highlights, but certianly won’t cover everything they did – so I’d suggest you watch that if you’re interested in the topic.
I’ll share a few highlights from the podcast that stood out to me. For context, Jayden Quinlan is the senior ballistician at Hornady, and he is often brought in on the more technical podcasts like this as a subject matter expert.
Seth: “In a given propellant, let’s say you got a cartridge like a 300 Win Mag, and the same propellant also works in a 6.5 Creedmoor or a 270 or something like that. Does the cartridge volume play into the sensitivity of a particular propellant?”
Jayden:“Yes. Absolutely.”
Seth: “That’s an important note because I feel like there are a lot of powders out there that people go, ‘Oh, I’m using Varget, so temperature stability is like 0.2 or 0.3 feet per second per degree. I don’t need to worry about it.’ But the problem is they’re going off anecdotal data, and depending on their individual cartridge volume, it could actually be maybe better or worse than what they thought.”
Miles Neville was also on this podcast, and he is a project manager at Hornady who works alongside Jayden. Miles has tested temperature sensitivity first-hand in their lab for a lot of different types of powders, cartridges, and loads. Miles also happens to be one of the pro shooters in the Precision Rifle Series, finishing 2nd overall in 2023 in the PRS Gas Gun Division and 101st in 2024 in the PRS Open Division. Here is something Miles said in the podcast that caught my attention:
“Even if a guy wants to be really picky and only use the good powders that are known to be insensitive to temperature like H4350, Varget, others in the Hodgdon Extreme line, or some of the Alliant powders that are really good – you can still see it. If you are going to be zeroing and setting things up at 70° F and then using that ammo below zero or when there are 50° or more difference – you are going to see the effects of that. It’s less common that people notice it because, for the most part, people don’t want to go out and shoot a match when it’s freezing – although some still do it. There is a creep in velocity, but some people may not notice it.” – Miles Neville
While I’ve known about powder temperature sensitivity for years, I am also a shooter who exclusively uses Hodgdon Extreme Series powders (primarily Varget, H4350, and H1000). To be clear, I’m not sponsored by Hodgdon (or anyone) – that choice is simply based on lots of experience and wanting to avoid the whole temperature sensitivity issue. But that means I’m pretty much the guy that the Hornady guys were talking about that was dismissing it because I was using Varget or another powder that is known to be less sensitive to swings in temperature. Those guys have tested more ammo than just about anyone – so it caused me to wonder if I might be glossing over something that I need to account for.
It is fairly rare for me to have elevation issues (i.e., miss a target high or low). Like other pro shooters, I verify that my dope is lining up with my Kestrel ballistic calculator before every major match. But, even if it is rare, we do all occasionally miss a target high or low. Could temperature sensitivity be one of the contributing factors?
I couldn’t shake that question from my brain, so I eventually had to test it for myself! Miles also mentioned a powder’s temperature sensitivity “is almost never linear from ambient to cold or ambient to hot.” So, I knew that I wanted to not just test two extremes and assume it would be linear between those two data points.
Jeff’s comments made me think I should test at the most extreme low temp I could see myself shooting in, which I thought would be close to 0° F. I also thought I should test just above freezing because the trend in velocity might vary as it crosses that crystalline threshold.
I ended up loading up 10 rounds to test around these temperatures:
- 5° F (Freezer)
- 33° F (Refrigerator)
- 58° F (Cold room)
- 76° F (Warm room)
- 108° F (Warming blanket)
I tested my 6mm Dasher match ammo that has Varget powder, and I also tested my 6mm Creedmoor match ammo that has H4350 powder. I fired 10 shots of each type of ammo at each temperature in my 100-yard underground tunnel. On the Hornady podcast, they mentioned that powder temperature sensitivity might not just change your velocity but could change your point of impact. So, I wanted to quantify any POI shift as well as measure the velocity over all those temperatures.
For each temperature, I wrapped the ammo in a towel with a Kestrel that was set to log the temperature every 2 minutes. Then, I put it in an environment that would acclimate it to the desired temperature range and left it for 8 hours. A study published in 2022 by the Journal of Ballistics investigated the temperature equilibration times of various ammunition calibers under different heating/cooling conditions. The study found “the equilibration time of the small-caliber ammunition is only 7-8 hours.” Once I pulled the ammo from the environment, I’d log the average temperature the Kestrel measured over the past hour, take the ammo to my tunnel, and shoot it immediately. Then, I’d let the barrel of the rifle cool to ambient temperature and repeat for the next set of ammo.
In full transparency, I measured the 76° batch first as the baseline – and I accidentally skewed those velocity measurements. So, I had to toss out that data, but I have 100% confidence in all the other data. And we’ll see in the data, that extra data-point wasn’t necessary to clearly see the pattern.
So, after carefully firing 100 rounds of ammo at a wide range of temperatures, here is what I found:
For the 6mm Dasher with ammo using Varget powder, I measured an average velocity over 10 rounds at 5° F of 2,821 fps, and at 108° F, the average was 2,835 fps. That is only a 14 fps velocity difference over a 103° temperature swing! That averages a 0.136 fps increase per degree over that range. You can see there was close to 0.2 fps per degree between 5° and 33°, but then only 0.1 fps per degree from 58° to 108°.
To put that into context, at 1000 yards that 14 fps difference would result in 3.75” of elevation error! So as long as I’m not shooting at a targets smaller than 8” tall at 1000 yards, it isn’t enough to result in a miss – even if my ammo temp 103°! The truth is, it would be a very extreme example for us to even see half of that swing.
Did I see any point of impact shift? Nope. That tiny change in velocity was not enough to cause any POI shift. But, here is the target I carefully measured to prove that was true. I fired 10 rounds at each temperature but split them into two 5-shot groups.
(Fun Fact: My average 5-shot group over all 10 groups measured 0.298 MOA! Thanks to TS Customs for chambering some impressive barrels from CRB! And no, I’m not sponsored by any of them.)
So, with the lot of Varget rifle powder that I’m currently loading out of my 6mm Dasher, I feel like I can safely ignore any effect of ambient temperature swings.
But what about the 6mm Creedmoor with the H4350 load? Here are the results for it:
It also showed very little temperature sensitivity. My average velocity was 3,088 fps at 5° and 3,102 fps at 105°. So we had a 14 fps increase over 100°, which is exactly 0.140 fps per degree. Funny enough, that is almost identical to what I measured for Varget! I was shocked they were so similar.
In the case of H4350, there wasn’t as much change from 5° to 35°. We saw 0.19 fps per degree with Varget in that coldest window but only 0.09 fps per degree with H4350. At least according to some forums, H4350 is a single-base powder, while Varget is a double-base powder. So maybe that makes sense – or maybe it’s a coincidence.
Once again, with just a 14 fps difference in velocity over a 100° swing – temperature sensitivity for my lot of H4350 powder from my 6mm Creedmoor seems to be in the noise for all practical purposes.
As I said at the start, while we’d love for the difference in muzzle velocity to be 0 fps over 100° – for practical purposes, it would take a closer to a 40 fps swing in my rifles to be the leading cause of missing a 20” target at 1,000 yards. I’d say the largest swing in temperature you might see in a single day might be 40°. So even if we had up to 1 fps per degree, it would put the shot off center but may not result in a miss.
Now, I’m not saying I’d be satisfied with that because it assumes your wind call was perfect, and you hit the very top or bottom of the plate. I prefer to stay more centered in the plate (as we all do) to leave myself a little more margin for aiming error, so I would probably be concerned with anything that showed 0.5 fps per degree or more. But, at least in my testing – Varget and H4350 were well below that threshold of being meaningful at 0.14 fps per degree.
That is a big reason why Varget and H4350 in the Hodgdon Extreme Series are the two favorite powders among the pros! 87% of the top 200 ranked shooters in the Precision Rifle Series (PRS) are using either Varget or H4350 in their match ammo (see all the data).
Please don’t let this convince you that you shouldn’t worry about this for other types of powders. There are absolutely some powders that cause shooters to start missing as the day warms up. I’ve seen it countless at matches! It used to be very prevalent, but over the last few years, several powder options have been introduced that are very temperature stable. My advice would be to use one of those two, but also test it yourself! That is the only way to know for sure.
Finally, let’s talk about what powders are the least sensitive to swings in temperature.
In general, single-base powders are less sensitive to temperature variations compared to double-base powders. Single-base powders contain only nitrocellulose, making them more temperature stable and ideal for precision shooting, while double-base powders include both nitrocellulose and nitroglycerin, providing higher energy but often increasing temperature sensitivity. Double-base powders are commonly used in magnum cartridges and military applications, whereas single-base powders are preferred for long-range consistency.
In the book Ammunition, Demystified, ballistic engineer Jeff Siewert went even deeper: “Propellants containing nitroglycerine (e.g., double-base or triple-base chemistries) have a reputation for sensitivity to cold-temperature conditions due to the crystalline transition temperature of nitroglycerine being just 15-20° C above the typical -40° C typically specified for operation of military propellants. Below this temperature, the grain can fracture in uncontrolled ways, causing a rapid increase in the burning area of the propellant and a resulting spike in peak pressure.” Jayden Quinlan, senior ballistician at Hornady, mentioned that same phenomenon on the Hornady podcast. (Note: We don’t use triple-base powders in small arms, so that isn’t relevant here.)
Now, that doesn’t mean that ALL double-base powders are highly sensitive to temperature or that all single-base powders are NOT sensitive to temperature. There are a number of techniques manufacturers use to try to mitigate this kind of temperature sensitivity, so unfortunately, it isn’t as easy as saying, “Single-base is always good, and double-base is always bad.” However, it is true that single-base powders are usually more stable across different temperatures, which makes them the preferred choice among many precision rifle shooters.
The Hornady team wrapped up the podcast with this million-dollar question:
Seth: “So you guys have done a bunch of testing. In the world of precision rifles, what are a couple of the best powders you’ve ever tested?”
Jayden: “The Hodgdon Extreme Series has the longest and best reputation. That is powders like H4350, Varget, H4381, H1000, Retumbo. The temperature stable series from Alliant is amazing and has had some of the lowest temperature sensitivity factors that I’ve ever seen – like zero!
Seth: “Those are propellants like Reloader 16, 23, 26, and 15.5. When Reloader 16, 23, and 26 first came out, I thought we were doing tests wrong! I thought, ‘Wait, this isn’t how it is supposed to work!’ It was especially surprising for some of those big charge weights, like a 300 PRC with 74 grains of Reloader 26 powder in there. You think there is going to be a pretty significant shift with temperature, but some of that stuff just didn’t budge.”
Jayden: “Then in some of the newer powders, the Winchester StaBall 6.5, StaBall HD, and StaBall Match – those 3 are very temperature stable.”
Miles: “Yeah, the StaBall HD and StaBall Match are more temperature stable than the StaBall 6.5. But again, in that Winchester StaBall family of powders, we’ve seen some that are effectively no change in velocity from -20° up to 140°. You are talking single-digit foot-per-second deltas from coldest to hottest, which is crazy. We’re used to seeing how many tens of feet per second it is going to be different – and then you see nothing. Wow! Okay!”
So, after years of extensive testing with an wide range of powders, cartridges, and loads, here are the rifle reloading powders that stuck out to Hornady engineers as being the least sensitive to swings in temperature:
- Hodgdon Extreme Series Powders, which includes H4350, Varget, H4381, H1000, Retumbo, H4381SC, H4895, H322, H4198
- Alliant Reloder Temperature Stable Series Powders, which includes Reloder 16, 23, 26, and 15.5.
- Winchester StaBall 6.5, StaBall HD, and StaBall Match
Unfortunately, in May 2024, Vista Outdoors (the company that bought Alliant Powders in 2015) posted this:
“Due to the worldwide shortage of nitrocellulose, the Vista Outdoor supply agreement for the sale of Alliant Powder canisters has been suspended for an unknown period. At this time, we have no timeline for the fulfillment and will be canceling outstanding Alliant orders in our system. Representatives will provide updates and coordinate new orders based on availability.”
So Alliant Reloder powders have suspended sales to the public indefinitely. There may be military or commercial ammo manufacturers still using it, but it’s not available for us reloaders for now. Hopefully, they will be again at some point in the future.
Temperature sensitivity in rifle powders is a real factor that can cause measurable shifts in velocity, and in extreme cases, it could mean the difference between hitting and missing a long-range target. While some powders exhibit significant changes in muzzle velocity across temperature swings, my testing of Varget and H4350 showed that they remained impressively stable—averaging just 0.14 fps per degree of temperature change. This confirms why these powders dominate among top PRS shooters. If you’re serious about precision shooting, choosing a temperature-stable powder is essential, but as always, the best approach is to test your specific load to ensure confidence in real-world conditions.
This article is part of a series on rifle reloading data, load development, and reloading components. Here are other related articles that I’ve recently published or plan to publish in the near future:
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