Home Forums Hunting & Shooting Ask The Gunwriters Temp Stable Powders – “Stop the Insanity"

Jordan,

I have seen POI shift as much as three inches at 100 yards with more than one handload that lost considerable velocity from 70 to zero F. It isn't common, but it happens, and you can't tell if it will unless you actually test the load in cold weather. Freezing only the ammo itself is not a reliable test. And the POI can change in ANY direction, not just up and down.

I have never seen any noticeable change in POI at 100 with a temperature-stable powder, and I have tested plenty at 70 and zero.

I've been on a couple of elk hunts when the temperature was right around zero. To me, it's worth the piece of mind to use a temperature stable powder.

Good report from the "far North" of Louisiana.

About the same deal here in Central Louisiana.

I may have to check out that area one of these days...

A man need to get out and explore, don't ya know...

DF

You're welcome any time!

Bingo. I've seen a POI change when the temps change with less than stable powders. The biggest was with RL-22 in a 270 and 150 grainers.

Casey,

Perhaps not so oddly, that was the combo that produced one of the worst POI shifts I've encountered as well. The load was VERY accurate at 70 degrees F.--and was still accurate at zero. But at zero degrees, POI shifted an inch up and three inches right.

And initially I was all excited because RL-22 made this slowish 270 about 75fps faster than H4831.............sheesh.

I’ve never experienced the above POI shifts with MRP in a 7mm Weatherby with loads worked up at 300 ft MSL at 50 degrees and checked at 7,000 ft MSL at 20 degrees. Maybe MRP is not really RL22 or the temp spread is not enough? Happy Trails

7977 for cold OR hot temps.

WAM,

20 to 50 degrees is indeed not much of a temperature spread.

In fact I have yet to encounter a modern smokeless powder that isn't pretty temp-stable at temperatures from around freezing to 80-85. Have also never tested one that doesn't increase noticeably in velocity (and hence pressure) above 85 degrees, though the more temp-resistant don't show as much rise.

Also, even many older powders vary considerably in temp-stability. Probably the worst are double-based powders, whether extruded or spherical--and all spherical powders are double-based. In general, the old IMR single-based powders are more temp-resistant than older double-based powders.

However, there are several factors that I've mentioned frequently in my writings on the subject, especially my chapter on temperature and powder in GUN GACK II. First, even pretty temp-sensitive powders can work pretty well in specific cartridges, or even specific cartridge/bullet combinations. Have seen this numerous times in my tests. In fact some powders specifically designed for certain cartridges are often very temperature-resistant in that specific round, but not so much in others. Ramshot TAC is a good example. It was specifically designed for the 5.56 and 7.62 NATO rounds, so tends to be very temp resistant in the .223 and .308, but not so much in other rounds.

Second, some powders are "accidentally" temp resistant. A prime example is Reloder 26, which was not specifically designed to be temp-resistant, as were RL-16 and RL-23. As a result, 26's temp-resistance can vary more when used in different rounds.

On the other hand, today's powders that were specifically designed to be temp-resistant in a wide range of applications work very well, including RL-16 and 23, the Hodgdon Extremes, and the IMR Endurons. I have yet to test any of them at both 70 F. and zero that show more than about a 25 fps difference in velocity.

Whether all this means anything to a certain hunter is another question. It does to me, since I often hunt in temperatures down around zero, or even colder, and sometimes shoot at ranges over 200 yards--and on rarer occasions have hunted in temperatures above 100.

Wouldn't changes in air density when going from warm weather to frigid weather have a deleterious effect on POI also?

Changes in air density make a HUGE difference in POI at longer ranges. Less dense air causes bullets to slow down less quickly, and thus drop less and hit the target with higher velocity than in more dense air. This is a part of environmental conditions that are factored into ballistics charts though, and I've never seen any noticeable shift in impact at 100 yards that wasn't due to a large drop in temperature/pressure/velocity. I do a lot of hunting at 6k-8k ASL, and the bullets fly a lot flatter there than at the usual 4k-4.5k ASL that I usually shoot at. Of course, during late-season elk hunting, it can be 20 or -20 degrees in the morning, and the air is a lot more dense than it would be at 50 degrees, but it varies less at higher elevation, because there is less air.

Thanks, John

I have read your articles in Rifle / Handloader and Gun Gack, too. I just mention the 7mm Weatherby anecdote as I rarely work up loads when it exceeds 50 F and usually hunt when it is between 10 - 60 F. I never hunt and rarely shoot centerfires if it is above 80F. Any warmer than that, maybe a coyote or other varmint with a .223!

gnoahhh,

Yes, air density has a HUGE effect on downrange POI, as huntnshot pointed out.

But as he pointed out, it almost never has a measurable effect on 100-yard POI--and as I pointed out, temperature[-sensitive powders sometimes do, often major.

Any way we can reduce (or eliminate) the effect of ANY variable helps in accurate shooting. Some we can't do anything about, except calculate their effect--such as air density. But these days we can do something about variations in muzzle velocity due to temperature.

Is this one of those situation that some refer to as "overthinking a potential problem"?

I kinda liked the statement about " I never had those problems" before the internet....
same here....

Runout probably didn't matter before the internet either.

In Internet oddity: Have noticed that many handloaders can apparently "read" pressures precisely by looking at fired primers, yet have never seen any detailed description of how this works on the Internet. You'd think something would have appeared by now.

R19 was the best powder in two .240 Weatherbys I used to have. However, R19 in a heavily compressed 338WM load, using the "slick as snot" older Barnes XLC 185 was perfect...at 60 degrees. When I tried it at 10 deg....patterns. At home, pulled the bullets and powder column was a solid 'cake", had to dig it out w/screwdriver! I jumped on some H4350, worked up a load next day, also 10deg. Nine days later I shot a real big cow elk right at 250yds! Now, this was more of a problem of very, very compressed powder in order to gain any real velocity from that slick bullet! The 338WM case was 'almost too small" for that bullet and many powders, couldn't get enough in there. A LEE FCD would have helped, "maybe", and I was all enamored with R19 for its speed and grand results in the 240W, ha.

I just loaded up some trial loads for my 300WM and the 150TTSX. I'm starting out with H4350 and H4831! ha I was going to use R23, but the mid range load almost filled the case! My Mesa has a long throat, this 150 TTSX touches the lands at 3.50", so set them at 3.45 and crimped them ( I always FCD Barnes anymore...just my thing...) I'm pretty sure I can get one of those Hodgdons to work.

In the early 80's I was probably the only guy in the valley with a chrono. It was not uncommon for shooters to come over and ask to run a couple rounds through my chrono. I met a couple silhouette shooters that way and made friends with them. They educated me to the concept of temp sensitivity of smokeless powder. We would get together at the range once or twice a year and cold test various loads.

Over the years the most stable powders have been H4350 and H4831 in cold weather testing, in a bunch of my own and other guys loads--this was even before the "Extreme" line of powders appeared.

Alliant powders have been claimed to be temp stable but I have seen some velocity loss even in the powders Alliant claims to be temp stable. And I mean every time that I can recall. When JB cold weather tested RL-26 in a 270 and found no velocity loss I had to try some--especially given the velocities RL-26 was getting. When I got around to testing RL-26 I lost 20-30 fps in two 270's and two 243's from 80-85 degrees down to about 15 degrees.

A call to Alliant and it was explained to me the "controlled response" of RL-26 means there most likely will be a smallish velocity loss with RL-26, but it will occur in a linear, and predictable, fashion. My experience has been at roughly 15-25 degrees is where a quick drop off of velocity occurs. I think JB has mentioned this before. The only way to confirm what the Alliant rep described is to test RL-26 at three different data points--80+ degrees, then at around 25-30 degress, and then in the low teens or single digits.

Casey,

In my 70 F./zero test with RL-26, using the 150 Partition and a max charge, 26 actually gained around 50 fps.

My "zero" tests are actually at -5 to +5 degrees, which is as close as I can come to zero under actual outdoor conditions, given the vagaries of weather. This is explained in my chapter on temperature and powder in GUN GACK II, which includes a bunch of tests in cartridges from the .17 HMR to .375 H&H. In fact in the tests with Extreme, Enduron and RL-16 and 23 powders usually show around 25-30 fps difference in velocity from 70 to zero, sometimes plus and sometimes minus.