Powder temp sensitivity chart
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linebaugh
Silver $$ Contributor
FWIW.
I assume the numbers change a bit based on cartridge size and caliber. I have fairly extensive data on my comp gun and N160 and I use a .7 FPS per degree offset. I allow for that offset in Strelok and it has not failed me.
If you have sloppy reloading practices and shoot in a smaller temp range environment you will probably have a hard ever seeing it. For example most of my shoots are in the summer from 75-95 degrees with the bulk being 80-90 degrees. At .7 fps per degree the bulk of my sholting environments run 7 FPS deviation. You would need to be hitting single digit ES to know that. And I freely admit I do not know mine exactly. More over I am stating that considering environmental factors vs loading practices I am probably wasting my time even working with it in my app.
I assume the numbers change a bit based on cartridge size and caliber. I have fairly extensive data on my comp gun and N160 and I use a .7 FPS per degree offset. I allow for that offset in Strelok and it has not failed me.
If you have sloppy reloading practices and shoot in a smaller temp range environment you will probably have a hard ever seeing it. For example most of my shoots are in the summer from 75-95 degrees with the bulk being 80-90 degrees. At .7 fps per degree the bulk of my sholting environments run 7 FPS deviation. You would need to be hitting single digit ES to know that. And I freely admit I do not know mine exactly. More over I am stating that considering environmental factors vs loading practices I am probably wasting my time even working with it in my app.
Most of these are developed from crowd-sourced data and aren't very reliable. Couple that with the fact that temperature sensitivity isn't linear, and both starting/ending temperature matter (0-10c isn't the same as 30-40c; you can't just X FPS per Y deg linearly calculate it) as well as cartridge/density and associated pressure levels. They're normally a good "is this in the top 20 or bottom 20" for sensitivity indicators, but not much good beyond that.
Ned Ludd
Silver $$ Contributor
I've seen three or four different versions of this chart [or similar] floating around at shooting forums at one time or another. Some of the values are the same as what you have, some are different. I'd take this info with a large grain of salt. Nothing wrong with using it as a rough guide, just be aware of the complexity and sheer number of variables involved in how powder burn rates are affected by temperature. As has been noted, it is not perfectly linear. In addition, pressure also has a direct effect on powder burn rate, so the burn rate of a specific powder can also differ depending on the cartridge size/shape and bullet weight, even when held at a constant temperature.
338 dude , interesting chart . I see they have AR comp almost twice as bad as IMR-4064 and yet Federal changed to AR-comp in the GMM cartridges because it’s supposed to be more temp stable .
I was of the impression that AR-comp was right up there with Varget and 8208xbr .
Any opinions on all that ?
I was of the impression that AR-comp was right up there with Varget and 8208xbr .
Any opinions on all that ?
It is funny when you check them in real world temps. with the gun and ammo at the same temperature as it is outdoors the numbers on the charts are way off. The H4350 and H4895 fall 1 foot per degree from 60 degrees to 40 degrees. They are better in the areas between 90 degrees and 60. Artificial testing is flawed..... jim
The chart is baloney. I’d like to think most serious shooters understand that without charge weight, barrel length, and temperatures the claims have no context to allow any useful conclusion. Temp sensitivity like barrel length effect is not linear.
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I recently asked Western powders about the temp sensitivity of their Ramshot line of powders. Here is their reply.
Most of our powders are not insensitive, and will show some effect at hot and cold temperatures.
However, we test at -40F and +125F and the deviation in most cases are ca 3% to 5% at these extreme levels. Therefore most shooters do not notice much difference under normal practical hunting conditions.
More elaboration on the subject:
Complete temperature stability can only be achieved with tubular extruded powders designs, either with double base (NG) and/or with other coating technologies.
Because the ballistic performance at extreme temperature is completely dependent on the specific combination, it is very difficult to quantify and qualify.
Our standard powders perform very well at extreme temperatures, and usually pass the strict military requirements by a large margin.
This is a subject that often fraught with misconceptions and inaccuracies.
The term is used loosely by manufacturers without qualifying the subject, and is obviously exploited for marketing purposes and perceptions.
The facts are:
It is also very important that when a comparison is made, that all conditions re weapon i.e. components primer, case, bullet and the velocity are equal, and preferably done at the same time on the same day.
Most of our powders are not insensitive, and will show some effect at hot and cold temperatures.
However, we test at -40F and +125F and the deviation in most cases are ca 3% to 5% at these extreme levels. Therefore most shooters do not notice much difference under normal practical hunting conditions.
More elaboration on the subject:
Complete temperature stability can only be achieved with tubular extruded powders designs, either with double base (NG) and/or with other coating technologies.
Because the ballistic performance at extreme temperature is completely dependent on the specific combination, it is very difficult to quantify and qualify.
Our standard powders perform very well at extreme temperatures, and usually pass the strict military requirements by a large margin.
This is a subject that often fraught with misconceptions and inaccuracies.
The term is used loosely by manufacturers without qualifying the subject, and is obviously exploited for marketing purposes and perceptions.
The facts are:
- Although powders can be improved, it’s really only possible with advanced coating procedures and additives which increase the cost.
- A particular powder can be improved re temperature stability for certain combinations, within a certain envelope which is specific to the following three main parameters/aspects
- The caliber.
- The weight of the projectile/bullet.
- The performance level.
It is also very important that when a comparison is made, that all conditions re weapon i.e. components primer, case, bullet and the velocity are equal, and preferably done at the same time on the same day.
urbanrifleman
Site $$ Sponsor
AR Comp, R16, and R23 are so temp insensitive they might as well be a flat line.
That chart is full of poop man.
That chart is full of poop man.
I’ve not used rl23 but absolutely can confirm AR comp and RL16 are rock solid.
urbanrifleman
Site $$ Sponsor
R23 is the same.
LVLAaron
Gold $$ Contributor
http://forum.accurateshooter.com/th...eaded-step-child.3986954/page-2#post-37577188
Straight from the horses mouth about AR-Comp. I can definitely confirm. AR-Comp is by far my favorite powder to use.
urbanrifleman
Site $$ Sponsor
Some people don't speak horse.
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