Temperature Sensitivity of 11 Powders for .308 Winchester

[vonb]

Great work and an informative post.

 

[6ShotsOr5?]

…Maybe it's a combination of both effects.

Both are important. Powder temperature affects the pressure developed and the muzzle velocity — internal ballistics. Higher air temperature along the line of flight reduces the air density which reduces the drag force on the bullet — external ballistics. Both can change a lot across the temperature range you described.

 

[old_heli_logger]

Is this what you're looking for?

 

[Dimner]

This post, I only just found it now. Bumping for those who have not read it as well as giving a big THANK you for doing this test.

 

[ebb]

So I may not have understood all that I should have from your test, but here is what I got. The powder that brags about temperature insensitivity the most was not. And the one that has held the line on prices better than all of them was the most temperature insensitive. And yes Thank You for your testing!

 

[Todd Morley]

You can also estimate temperature sensitivity using QuickLOAD, by calculating the muzzle velocities at two temperatures, and dividing the difference in estimated muzzle velocities by the difference in temps. For example, QL estimates muzzle velocity for a Berger 230-grain OTM 0.308 bullet coming out of my 28" barrel 300 RUM at 2893, at 70 degrees F. At 20 degrees F it becomes 2805, making the temperature sensitivity of LRT (2893 - 2805) / (70 - 20) = 88 / 50 = 1.76 fps/degree.

I have learned to develop loads for specific temperature ranges, by developing the load in the middle of the temperature range I expect to hunt. For instance, I developed the above load at 45 degrees F, to minimize the expected temperature deviation from the temperature at which I tuned the load. This minimizes my calculations' error due to error in the estimate of the powder's temperature sensitivity. . . .

 

[Doom]

January 2022 lot number on my N150. The older powders are supposed to be less temperature stable which I confirmed for N140. I don't have experience with the older N150.

The Formulations for the temperature sensitivity change in/about 2016.