Each precision shooter needs consistency, however powder temperature sensitivity can introduce a variable that many overlook. As outdoors air temperatures rise or fall, a powder’s burn charge modifications, altering muzzle velocity and shifting a bullet’s level of influence. Some powders are much less affected by swings in temperature than others, however many introduce sufficient variation to trigger a miss – particularly at prolonged distances.
This text will dive into:
Recommendation from ballisticians and business consultants on powder temperature sensitivity
Quantify what which means in the actual world
Share first-hand take a look at outcomes of the most well-liked powders
Itemize a listing of among the most temperature-stable rifle powders
My final article shared load growth suggestions from Jeff Siewert, a ballistic engineer with 40 years of business expertise. Jeff defined that the particular powder we select has a direct influence on the scale of our teams. Some powders are significantly better than others when it comes to maximizing the precision of your rifle.
Jeff’s final level when it got here to selecting the optimum powder for excessive precision was this: “The propellant has a low temperature coefficient; its efficiency just isn’t overly delicate to will increase or decreases in ambient temperature.”
All powders will change to some extent primarily based on the ambient temperature of the powder, however some are way more delicate than others.
“As a long-range shooter and precision rifle competitor, temperature sensitivity is one thing all of us have to be educated of and at various levels involved with. There are situations you will get away with lots of issues and never have any concern, not even figuring out it exists, however there are additionally occasions when, in the event you don’t account for it, you begin stretching the legs on what you’re taking pictures you’re going to overlook the goal merely due to the temperature sensitivity of the propellant.” – Seth Swerczek, Hornady Advertising Communications Supervisor
Handloader Journal printed this powder temperature sensitivity chart, which exhibits what they’ve measured through the years when it comes to variance in velocity with the identical load at totally different temperatures. For one load, they discovered a rise of 87 fps from the load being at 70° to 115° F! That is a rise of 1.9 fps per diploma change!
Actual-World Instance of How A lot Powder Temperature Sensitivity Issues
Let’s say a match began at 40° F and climbed to 80° by afternoon (frequent in west Texas, the place I reside). We’ll use the 1.9 fps per diploma distinction that Handloader Journal reported. Let’s say our muzzle velocity began at 2800 fps on Stage 1, however because the temperature rose to 80°, our MV climbed to 2876 by the final stage. If our elevation adjustment on a goal at 1000 yards was completely centered once we began – we’d be hitting over 20” larger by the point we completed! We aren’t taking pictures 4-foot-tall targets in matches, so you possibly can see how even a fraction of that temperature sensitivity may put you off the plate. In truth, it will solely take a 37 fps improve over that 40-degree swing, and it will doubtless trigger us to overlook a 20” tall goal at 1000 yards.
The instance above assumes that every part else was excellent! You broke the shot completely, the vary was 100% correct, your ballistic answer was 100% correct, your wind name was excellent, and your bullet went completely into the middle of your group (plus a number of different issues). If any of these issues have been off, we may find yourself off the plate with even much less velocity change.
Whereas we’d like to have completely no variation in our velocity, it looks as if the sensible objective for long-range shooters is that we want the variation to be lower than 1 fps per diploma Fahrenheit. How far below 1.0 you need will range from one individual to a different and primarily based on the applying – however we will in all probability all agree that 1.0 fps per diploma or extra is an excessive amount of for precision long-range taking pictures.
Remember that the skin temperature doesn’t should be 115° in your ammo to succeed in 115°. For those who go away your ammo within the solar on prime of a darkish floor, the ambient temperature of the powder contained in the case can get there fairly shortly. In spite of everything, we aren’t speaking in regards to the ambient air temperature however the temperature of the gunpowder itself in the intervening time of ignition. That’s typically associated to ambient outdoors air temperature, however not at all times.
A number of months in the past, Hornady printed a 1-hour podcast targeted on powder temperature sensitivity. Their hopes have been to make it simpler to know, calculate, and account for. I’ll share a couple of highlights, however certianly gained’t cowl every part they did – so I’d recommend you watch that in the event you’re within the subject.
I’ll share a couple of highlights from the podcast that stood out to me. For context, Jayden Quinlan is the senior ballistician at Hornady, and he’s typically introduced in on the extra technical podcasts like this as a topic knowledgeable.
Seth: “In a given propellant, let’s say you bought a cartridge like a 300 Win Magazine, and the identical propellant additionally works in a 6.5 Creedmoor or a 270 or one thing like that. Does the cartridge quantity play into the sensitivity of a specific propellant?”
Jayden: “Sure. Completely.”
Seth: “That’s an vital notice as a result of I really feel like there are lots of powders on the market that individuals go, ‘Oh, I’m utilizing Varget, so temperature stability is like 0.2 or 0.3 ft per second per diploma. I don’t want to fret about it.’ However the issue is that they’re going off anecdotal knowledge, and relying on their particular person cartridge quantity, it may truly be possibly higher or worse than what they thought.”
Miles Neville was additionally on this podcast, and he’s a mission supervisor at Hornady who works alongside Jayden. Miles has examined temperature sensitivity first-hand of their lab for lots of various kinds of powders, cartridges, and hundreds. Miles additionally occurs to be one of many professional shooters within the Precision Rifle Sequence, ending 2nd total in 2023 within the PRS Fuel Gun Division and one hundred and first in 2024 within the PRS Open Division. Right here is one thing Miles mentioned within the podcast that caught my consideration:
“Even when a man needs to be actually choosy and solely use the great powders which are identified to be insensitive to temperature like H4350, Varget, others within the Hodgdon Excessive line, or among the Alliant powders which are actually good – you possibly can nonetheless see it. If you’ll be zeroing and setting issues up at 70° F after which utilizing that ammo under zero or when there are 50° or extra distinction – you’ll see the results of that. It’s much less frequent that individuals discover it as a result of, for probably the most half, individuals don’t wish to exit and shoot a match when it’s freezing – though some nonetheless do it. There’s a creep in velocity, however some individuals could not discover it.” – Miles Neville
Whereas I’ve identified about powder temperature sensitivity for years, I’m additionally a shooter who solely makes use of Hodgdon Excessive Sequence powders (primarily Varget, H4350, and H1000). To be clear, I’m not sponsored by Hodgdon (or anybody) – that selection is solely primarily based on a number of expertise and eager to keep away from the entire temperature sensitivity concern. However which means I’m just about the man that the Hornady guys have been speaking about that was dismissing it as a result of I used to be utilizing Varget or one other powder that’s identified to be much less delicate to swings in temperature. These guys have examined extra ammo than simply about anybody – so it brought about me to marvel if I may be glossing over one thing that I must account for.
It’s pretty uncommon for me to have elevation points (i.e., miss a goal excessive or low). Like different professional shooters, I confirm that my dope is lining up with my Kestrel ballistic calculator earlier than each main match. However, even whether it is uncommon, we do all sometimes miss a goal excessive or low. May temperature sensitivity be one of many contributing components?
PRB’s Powder Temperature Sensitivity Discipline Check
I couldn’t shake that query from my mind, so I finally needed to take a look at it for myself! Miles additionally talked about a powder’s temperature sensitivity “is nearly by no means linear from ambient to chilly or ambient to scorching.” So, I knew that I needed to not simply take a look at two extremes and assume it will be linear between these two knowledge factors.
Jeff’s feedback made me suppose I ought to take a look at on the most excessive low temp I may see myself taking pictures in, which I assumed could be near 0° F. I additionally thought I ought to take a look at simply above freezing as a result of the development in velocity may range because it crosses that crystalline threshold.
I ended up loading up 10 rounds to check round these temperatures:
5° F (Freezer)
33° F (Fridge)
58° F (Chilly room)
76° F (Heat room)
108° F (Warming blanket)
I examined my 6mm Dasher match ammo that has Varget powder, and I additionally examined my 6mm Creedmoor match ammo that has H4350 powder. I fired 10 pictures of every kind of ammo at every temperature in my 100-yard underground tunnel. On the Hornady podcast, they talked about that powder temperature sensitivity won’t simply change your velocity however may change your level of influence. So, I needed to quantify any POI shift in addition to measure the speed over all these temperatures.
For every temperature, I wrapped the ammo in a towel with a Kestrel that was set to log the temperature each 2 minutes. Then, I put it in an atmosphere that will acclimate it to the specified temperature vary and left it for 8 hours. A examine printed in 2022 by the Journal of Ballistics investigated the temperature equilibration occasions of varied ammunition calibers below totally different heating/cooling situations. The examine discovered “the equilibration time of the small-caliber ammunition is just 7-8 hours.” As soon as I pulled the ammo from the atmosphere, I’d log the typical temperature the Kestrel measured over the previous hour, take the ammo to my tunnel, and shoot it instantly. Then, I’d let the barrel of the rifle cool to ambient temperature and repeat for the following set of ammo.
In full transparency, I measured the 76° batch first because the baseline – and I by accident skewed these velocity measurements. So, I needed to toss out that knowledge, however I’ve 100% confidence in all the opposite knowledge. And we’ll see within the knowledge, that additional data-point wasn’t obligatory to obviously see the sample.
Powder Temperature Sensitivity Check for Varget in my 6 Dasher
So, after rigorously firing 100 rounds of ammo at a variety of temperatures, here’s what I discovered:
For the 6mm Dasher with ammo utilizing Varget powder, I measured a mean velocity over 10 rounds at 5° F of two,821 fps, and at 108° F, the typical was 2,835 fps. That’s solely a 14 fps velocity distinction over a 103° temperature swing! That averages a 0.136 fps improve per diploma over that vary. You may see there was near 0.2 fps per diploma between 5° and 33°, however then solely 0.1 fps per diploma from 58° to 108°.
To place that into context, at 1000 yards that 14 fps distinction would end in 3.75” of elevation error! So so long as I’m not taking pictures at a targets smaller than 8” tall at 1000 yards, it isn’t sufficient to end in a miss – even when my ammo temp 103°! The reality is, it will be a really excessive instance for us to even see half of that swing.
Did I see any level of influence shift? Nope. That tiny change in velocity was not sufficient to trigger any POI shift. However, right here is the goal I rigorously measured to show that was true. I fired 10 rounds at every temperature however cut up them into two 5-shot teams. (Enjoyable Truth: My common 5-shot group over all 10 teams measured 0.298 MOA! Due to TS Customs for chambering some spectacular barrels! And no, I’m not sponsored by them.)
So, with the lot of Varget rifle powder that I’m presently loading out of my 6mm Dasher, I really feel like I can safely ignore any impact of ambient temperature swings.
Powder Temperature Sensitivity Check for H4350 in my 6mm Creedmoor
However what in regards to the 6mm Creedmoor with the H4350 load? Listed below are the outcomes for it:
It additionally confirmed little or no temperature sensitivity. My common velocity was 3,088 fps at 5° and three,102 fps at 105°. So we had a 14 fps improve over 100°, which is strictly 0.140 fps per diploma. Humorous sufficient, that’s virtually similar to what I measured for Varget! I used to be shocked they have been so comparable.
Within the case of H4350, there wasn’t as a lot change from 5° to 35°. We noticed 0.19 fps per diploma with Varget in that coldest window however solely 0.09 fps per diploma with H4350. No less than based on some boards, H4350 is a single-base powder, whereas Varget is a double-base powder. So possibly that is smart – or possibly it’s a coincidence.
As soon as once more, with only a 14 fps distinction in velocity over a 100° swing – temperature sensitivity for my lot of H4350 powder from my 6mm Creedmoor appears to be within the noise for all sensible functions.
As I mentioned at first, whereas we’d love for the distinction in muzzle velocity to be 0 fps over 100° – for sensible functions, it will take a more in-depth to a 40 fps swing in my rifles to be the main reason for lacking a 20” goal at 1,000 yards. I’d say the biggest swing in temperature you may see in a single day may be 40°. So even when we had as much as 1 fps per diploma, it will put the shot off middle however could not end in a miss.
Now, I’m not saying I’d be happy with that as a result of it assumes your wind name was excellent, and also you hit the very prime or backside of the plate. I want to remain extra centered within the plate (as all of us do) to go away myself a bit extra margin for aiming error, so I’d in all probability be involved with something that confirmed 0.5 fps per diploma or extra. However, at the least in my testing – Varget and H4350 have been nicely under that threshold of being significant at 0.14 fps per diploma.
That may be a huge motive why Varget and H4350 within the Hodgdon Excessive Sequence are the 2 favourite powders among the many professionals! 87% of the highest 200 ranked shooters within the Precision Rifle Sequence (PRS) are utilizing both Varget or H4350 of their match ammo (see all the info).
Please don’t let this persuade you that you just shouldn’t fear about this for different sorts of powders. There are completely some powders that trigger shooters to start out lacking because the day warms up. I’ve seen it numerous at matches! It was once very prevalent, however over the previous few years, a number of powder choices have been launched which are very temperature secure. My recommendation could be to make use of a type of two, but in addition take a look at it your self! That’s the solely solution to know for certain.
The Finest Rifle Powders For Low-Temperature Sensitivity
Lastly, let’s discuss what powders are the least delicate to swings in temperature.
Generally, single-base powders are much less delicate to temperature variations in comparison with double-base powders. Single-base powders include solely nitrocellulose, making them extra temperature secure and preferrred for precision taking pictures, whereas double-base powders embrace each nitrocellulose and nitroglycerin, offering larger vitality however typically rising temperature sensitivity. Double-base powders are generally utilized in magnum cartridges and navy functions, whereas single-base powders are most well-liked for long-range consistency.
Within the guide Ammunition, Demystified, ballistic engineer Jeff Siewert went even deeper: “Propellants containing nitroglycerine (e.g., double-base or triple-base chemistries) have a status for sensitivity to cold-temperature situations because of the crystalline transition temperature of nitroglycerine being simply 15-20° C above the standard -40° C sometimes specified for operation of navy propellants. Beneath this temperature, the grain can fracture in uncontrolled methods, inflicting a speedy improve within the burning space of the propellant and a ensuing spike in peak stress.” Jayden Quinlan, senior ballistician at Hornady, talked about that very same phenomenon on the Hornady podcast. (Word: We don’t use triple-base powders in small arms, in order that isn’t related right here.)
Now, that doesn’t imply that ALL double-base powders are extremely delicate to temperature or that every one single-base powders are NOT delicate to temperature. There are a variety of methods producers use to attempt to mitigate this sort of temperature sensitivity, so sadly, it isn’t as straightforward as saying, “Single-base is at all times good, and double-base is at all times dangerous.” Nevertheless, it’s true that single-base powders are normally extra secure throughout totally different temperatures, which makes them the popular selection amongst many precision rifle shooters.
The Hornady staff wrapped up the podcast with this million-dollar query:
Seth: “So that you guys have accomplished a bunch of testing. On the planet of precision rifles, what are a few the very best powders you’ve ever examined?”
Jayden: “The Hodgdon Excessive Sequence has the longest and finest status. That’s powders like H4350, Varget, H4381, H1000, Retumbo. The temperature secure sequence from Alliant is wonderful and has had among the lowest temperature sensitivity components that I’ve ever seen – like zero!
Seth: “These are propellants like Reloader 16, 23, 26, and 15.5. When Reloader 16, 23, and 26 first got here out, I assumed we have been doing assessments improper! I assumed, ‘Wait, this isn’t how it’s speculated to work!’ It was particularly shocking for a few of these huge cost weights, like a 300 PRC with 74 grains of Reloader 26 powder in there. You suppose there’s going to be a reasonably important shift with temperature, however a few of that stuff simply didn’t budge.”
Jayden: “Then in among the newer powders, the Winchester StaBall 6.5, StaBall HD, and StaBall Match – these 3 are very temperature secure.”
Miles: “Yeah, the StaBall HD and StaBall Match are extra temperature secure than the StaBall 6.5. However once more, in that Winchester StaBall household of powders, we’ve seen some which are successfully no change in velocity from -20° as much as 140°. You’re speaking single-digit foot-per-second deltas from coldest to hottest, which is loopy. We’re used to seeing what number of tens of ft per second it will be totally different – and you then see nothing. Wow! Okay!”
So, after years of intensive testing with an wide selection of powders, cartridges, and hundreds, listed below are the rifle reloading powders that caught out to Hornady engineers as being the least delicate to swings in temperature:
Hodgdon Excessive Sequence Powders, which incorporates H4350, Varget, H4381, H1000, Retumbo, H4381SC, H4895, H322, H4198
Alliant Reloder Temperature Steady Sequence Powders, which incorporates Reloder 16, 23, 26, and 15.5.
Winchester StaBall 6.5, StaBall HD, and StaBall Match
The Dangerous Information About Alliant Reloder Powders
Sadly, in Could 2024, Vista Outdoor (the corporate that purchased Alliant Powders in 2015) posted this:
“As a result of worldwide scarcity of nitrocellulose, the Vista Outside provide settlement for the sale of Alliant Powder canisters has been suspended for an unknown interval. Presently, we’ve got no timeline for the success and will likely be canceling excellent Alliant orders in our system. Representatives will present updates and coordinate new orders primarily based on availability.”
So Alliant Reloder powders have suspended gross sales to the general public indefinitely. There could also be navy or industrial ammo producers nonetheless utilizing it, however it’s not obtainable for us reloaders for now. Hopefully, they are going to be once more sooner or later sooner or later.
The Take-Away
Temperature sensitivity in rifle powders is an actual issue that may trigger measurable shifts in velocity, and in excessive instances, it may imply the distinction between hitting and lacking a long-range goal. Whereas some powders exhibit important modifications in muzzle velocity throughout temperature swings, my testing of Varget and H4350 confirmed that they remained impressively secure—averaging simply 0.14 fps per diploma of temperature change. This confirms why these powders dominate amongst prime PRS shooters. For those who’re critical about precision taking pictures, selecting a temperature-stable powder is crucial, however as at all times, the very best strategy is to check your particular load to make sure confidence in real-world situations.
Coming Up Subsequent
This text is a part of a sequence on rifle reloading knowledge, load growth, and reloading parts. Listed below are different associated articles that I’ve not too long ago printed or plan to publish within the close to future:
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