Home Forums Hunting & Shooting Ask The Gunwriters Is RL 26 Temperature Sensitive?

In the interest of science I have decided to test this theory this morning. I developed a load for my 7MM Remington Magnum this summer using 145 LRX’s and RL 26. Previous to this I have used that combination to literally shoot the barrel out of a Mashburn. Loads were developed at plus 20 degrees Celsius and final sight in done at around plus 25.

Today I’m hunting in minus 15 (Celsius) and am hiking past my 1000 yard range. Accessibility to this range is now by a considerable hike only. What an opportunity. I set up at 400 and 500 yards and have discovered that my zero has not changed. At all. Hmmm.

Off to light a fire. It’s cold. :-)

Shoot it at 100 yards and see how much change you get. At 400-500 yards, you aren't going to know if your zero has changed or not because wind can change POI. Group size at that distance will likely change though. Your test is not real valid, unless you can post a nice 100 yard target while shot in the cold weather, like you did when it was 70 degrees f.

I've used R-26 a bunch in cold weather with no negative effects, when it gets hot 95-100 Deg. R-26 pressure spikes in my loads, I load summer ammo and winter ammo for my Truck Guns. Rio7

Great info, thanks much.

BSA, it is valid and here is why. My target is not my zero. Nor do I care where the point of impact is at 100 yards. I’m using a “ballistic reticle” so this is how I zero the rifle. Knowing my subtention, my velocity etc I can come pretty close to knowing where zero needs to be to take advantage of my hash marks. A 250 yard zero with this load puts hash mark number one on at about 400 yards (actual zero was 391) and hash mark number two at an actual 500. This was all verified at 25 degrees Celsius in August.

This morning, in dead calm conditions with snow lightly falling I figured I had a perfect opportunity. I’d been hiking for five miles so everything was cold. No pretending. I ranged 391 yards and shot my 4” gong with hash mark number 1. Bang on. I went to 500 and shot my 10” gong and struck 2” left of centre. Keep in mind I’m just shooting off of my pack.

Now we can shoot at 100 yards all we like, but that’s not what this rifle is for. This morning I verified, without a doubt, that I could have killed an elk or a whitetail buck at anywhere from 10 to 500 yards with a load using RL 26. Zero has not changed in a 40 degree Celsius temperature swing.

That seems to be the consensus. But if it hits 95 where I’m from we have problems bigger than RL 26 :-)

Doesn't ammo in a truck gun stay roughly the same temp??😎😎

10 gaugemag,


My truck and Jeeps don't have A.C. they get hot. Rio7

That can happen, depending on the individual rifle and barrel weight.

What I do know in one of my hunting rifles with a light barrel, a Jack O'Connor Tribute that has been very accurate since first fired, is that point-of-impact with a maximum RL-26 load with the 150 Nosler Partition changed 1.5" at 100 yards from 70 to zero degrees F., apparently due to a velocity drop of around 60 fps.

Have never seen that much velocity drop or change in POI with any powder that's claimed to be temperature-resistant.

Which is why I always encourage hunters who might hunt in real cold (whether zero F. or -15 C.) to test their load and rifles if possible beforehand. And if they can't do that, then use a powder that is claimed to be temp-resistant.

What Alliant claims for RL-26 these days is "Reloder 26 has a high bulk density that allows larger powder charges, and it provides a consistent, controlled response to temperature changes." That is not exactly claiming it's temperature resistant. When RL-26 first appeared they said that while it wasn't specifically designed to be temp-resistant, it tended to be.

But as I have pointed out a number of times over the years, many powders can be very temp-resistant in specific applications, but not in others. This is more completely described in Chapter 15 of The Big Book of Gun Gack II.

Thanks for the detailed description of your test.

I have read the aforementioned temperature test chapter in GG2 and I’m not taking any issue with its findings, but can only comment on my experience with RL26. I worked up loads in my .300 Weatherby in conditions 40-50 degrees F with 168 gr TTSX and 215m primers. I zeroed at temps in the 40’s and checked it pre hunt several consecutive years at temps from 50 to 20 F and didn’t see a POI shift. It is my go-to load for my elk rifle and it seems to be stable in the temperature range I use it in, so I’m happy with the results with RL26. Since it is made from Unobtainium these days, I don’t use it for other loads or do too much target shooting.

PS: I won’t be found hunting outside of a heated blind if temps drop below the teens!

I have two loads with Rel 26 for a couple of my 270's. Going to be cold the next few days, will go to the range and verify zero and velocity.

I often try to work up my loads when it is a bit warmer, like 60-80F. Things tend to work out okay, as I don't shoot hunting rifles much above 85-90F or below 30F. RL26 loads have been fine at 90F at the range. RL17 did bite me once at 90-95F, so I've quit shooting that powder in the summer months.

Stuff like this doesn’t matter in 99% of big game hunting scenarios. Fortunately.

i have also notice in colder weather some different brand primers can make a difference , i prefer Federal primers when its cold .

SAAMI 22-250 1:8 22" shooting 75 A-Max @ 3275 via R-26. My ammo stays in my pickup. My pickup mostly sits outside. Our ambient temp high and low for 2023 so far have been:

-22F and 98F

I suspect on the 98F day, it was an awful lot hotter than 98F inside my pickup.

With my 270 I worked up loads in mild temps for my area(60-70). When I shot some when the temps were approaching triple digits, the loads were WAY over pressure (sticky bolt lift and obvious brass flow). Had to pull the loads down and reduce charge because sometimes it gets hot in Arizona.

As I have mentioned a number of times in my writings about temperature-resistant powders, the results from just about any present day smokeless rifle powder won't vary significantly in results between about 25 and 80 degrees F.

In general temperatures down around zero F. (or -15 to -20 C.) are where things can get wonky, because quite a few powders still lose considerable velocity, but even then the point-of-impact also depends on the specific rifle.

The test I ran with RL-26 where point-of-impact shifted about 1-1-2" at 100 yards was done in my O'Connor Tribute Model 70 Featherweight, where the light-weight barrel is free-floated. The loss of velocity that caused that shift was around 60 fps. In another .270 with a heavier barrel there was no POI shift with RL-26 and 150s, even though the load lost a similar amount of velocity.

Eileen's primary big game rifle for years was her Ultra Light Arms .257 Roberts Model 20, and its primary load was 47.0 grains of Ramshot Hunter and a 100-grain Barnes TTSX. While the other three Belgian-made Ramshot rifle powders (TAC, Big Game and Magnum) have been very cold-resistant in my tests at zero F., Hunter has lost around 100 fps from 70 to zero in more than one rifle.

But this didn't make any difference in 100-yard POI in the ULA .257, no doubt due to the medium-weight Douglas No. 2 barrel--and it being fully bedded (like all ULA/NULA rifles) in their very stiff synthetic stocks. And retaining POI is far more important than loss of velocity.

However, losing more velocity in really cold temperatures can affect POI, even in stiffer barrels. Both RL-22 and the old military surplus H4831 lost more than 100 fps from 70 to zero F. in my tests done in 1990 with a Remington .270, when I first became very curious about cold's effect.

This was because I'd shot a mule deer doe at down around zero. The range was about 200 yards, and I aimed behind the shoulder at the broadside doe, because obviously the main reason to take a doe is meat. Instead the 150-grain Nosler Partition (I was also hunting elk) landed in the center of the shoulder, around six inches to the right of where I'd aimed, and I shot from prone with a Remington Model 78 .270 Winchester (a cheaper version of the 700) with the same fairly stout barrel contour.

Which is why I performed my first cold test a couple days later, leaving the rifle and ammo in my pickup overnight when the temperature was predicted to drop to around zero. This was when I had my own 100-yard range on our 7-acre property six miles from town, so it was easy to test the rifle over my permanent benchrest and chronograph the results. (The chronograph was kept warm in the house.)

The point-of-impact of the 150/RL-22 load shifted three inches right during the test--which explained why the bullet landed in the doe's shoulder and not the ribs. But I had also worked up a load with mil-surp H4831 and the 130-grain Nosler Solid Base (the precursor of the Ballistic Tip), which at 70 degrees shot to the same point of impact as the 150-grain load--and into the same sub-inch group. So I tested the 130-grain load as well. It did not change POI, but groups opened up to almost 2 inches.

The 130-grain load lost 151 fps, and the 150-grain 129 fps. As I did more tests this much velocity loss turned out to be common with many powders of the day, but a few years later Hodgdon introduced the Extreme version of H4831, which has never shifted POI in the same test, with a variety of other rifles and cartridges--because the velocity difference between 70 and zero has never varied more than about 25 fps.

All of this is described in far more length and detail in Chapter 10 of The Big Book of Gun Gack II, along with results of both heat and cold tests with various powders in cartridges from the .17 Hornady Hornet to the .375 H&H Magnum. However, most hunters prefer simpler, Internet-length "sound bite" explanations--including Campfire members.

But it's not that simple, which is why I always suggest hunters test their ammo (whether factory or handloads) in as close to the conditions they might be hunting in as possible, if temperatures vary very far from "normal," whether cold or heat. Oh, and I have yet to find any powder that doesn't gain considerable velocity (and hence pressure) in temperatures over about 80 degrees--which like velocity loss in cold temps may or may not affect POI. But you won't know unless you test it.

Which is also why I prefer the term "temperature resistant" to "temperature insensitive" when referring to any smokeless powder.

Lots of severe cold weather poor shooting gets blamed on gear. But it’s hard to mimick t-shirt bench rest results when you can’t feel your fingers, up to your neck in snow, with a puffy parka on.

my rule of thumb is load down with less powder in hot weather while target shooting and if its cold conditions when i hunt i use close to max powder from reloading books with a 1 1/2 inch above the 1 inch square in the target . my 220 Swift Ruger #1 rides with me in the truck every day of the year and yes temperature has saved the life of a few coyotes .

That isn’t a plan, it’s a WAG.