Powder Temperature Sensitivities

[xswanted]

Yep, we’ve all been through about every thread and article regarding powder being sensitive to extreme temp swings.

Most tests test powder at 125 or so degrees and as cold as the can get it, typically around 25-30 degrees. The common “sensitive” powders show expected results as do the “non-sensitive” powders.

That test covers the majority of situations where powder temp sensitivity is crucial to performance and safety. You’re looking at roughly a 100 degree swing in temperature.

My curiosity and personal use for powder temperature sensitivity test revolves around colder temps with less of a swing in total air temperature variation, however the swing happens at the extreme end of the spectrum.

Has anyone tested powder from developing a load at 25-30 degrees and tested it down to -20 or colder? That gives a window of roughly 50 degrees in difference from top to bottom but that particular temperature is what my personal situation revolves around.

I hunt coyotes quite often in extreme cold and temps can and do dip down in ND to well below the donut much of the winter. I’ve always wondered if the same powders that are stable at “normal” temps are oblivious to the extreme cold or do they react?

Also do the “sensitive” powders level off so to speak at a certain temp, or do they continue to slow down as they get colder?

Opinions?

Thoughts?

Any suggestions on testing this so it is fairly accurate?

 

[Mulligan]

This may help
CW

Edit to include link

http://forum.accurateshooter.com/threads/why-is-ar-comp-the-red-headed-step-child.3986954/

 

[urbanrifleman]

Haha it's pretty funny... I was told the whole subject was boring and a waste of time....

Yet, its still one of the most repeated subjects duscussed here since.

You can do your own test. You just need some dry ice.

 

[cem]

The only broad range test to extreme temperatures I've heard about was long ago in Norma's Gun Bug's Guide. The discussion was in certifying powders for aircraft cannon at Negative 40 which isn't far from the same thing Fahrenheit and Centigrade. Norma asserted that all of their powders would work- not the same thing as asserting little or no variation.

Given that temperature sensitivity, especially corner cases, varies with the cartridge; that is loading density certainly, and probably powder amount and column shape as well as bore size affect temperature sensitivity I do believe that generalizing too much is pretty useless and doing one's own tests in one's own rig pays. When I lived at 9,000 feet it was easy to test at extreme temperatures. Since I've moved to town it's harder and I'm just as happy that way.

 

[xswanted]

View attachment 1143931
This may help
CW

Edit to include link



http://forum.accurateshooter.com/threads/why-is-ar-comp-the-red-headed-step-
child.3986954/

That is a good thread and test. Pretty much on the track of what I’m looking for.

 

[Gappmast]

I don't worry about powder sensitivity at -20 degrees I stay home by the fire.

 

[r bose]

I don't worry about powder sensitivity at -20 degrees I stay home by the fire.

HAHA, Don't know about you but I've never shot in 170 degrees either!!! Where I live my "range of temp swing" is about 40 above zero to 90. Only 50 degrees in total

 

[urbanrifleman]

HAHA, Don't know about you but I've never shot in 170 degrees either!!! Where I live my "range of temp swing" is about 40 above zero to 90. Only 50 degrees in total

Which is why most people say their powders are not temp sensitive. Between those numbers you might only see density effects mostly. Some of it will be the powder, but a small percentage.

 

[Straightshooter1]

HAHA, Don't know about you but I've never shot in 170 degrees either!!! Where I live my "range of temp swing" is about 40 above zero to 90. Only 50 degrees in total

LOL, yeah. . . I've never shot in 170° either, but have in 115° here in Arizona where it can get to 120°F. But. . . even if the ambient temperature isn't that high the temperatures inside a cartridge can sure get to be 170° if one has them sitting in the hot sun and/or in a hot interior of a vehicle OR in a hot chamber. For sure, they'd be really hot to handle at 170°F. Anyway, I make every effort to not do that.

 

[urbanrifleman]

LOL, yeah. . . I've never shot in 170° either, but have in 115° here in Arizona where it can get to 120°F. But. . . even if the ambient temperature isn't that high the temperatures inside a cartridge can sure get to be 170° if one has them sitting in the hot sun and/or in a hot interior of a vehicle OR in a hot chamber. For sure, they'd be really hot to handle at 170°F. Anyway, I make every effort to not do that.

Never happen... all good shooters only shoot in the shade, in a temperate climate.

Heathen... hahahaha

 

[Straightshooter1]

Never happen... all good shooters only shoot in the shade, in a temperate climate.

Heathen... hahahaha

Oh yeah.

 

[Zero333]

To do a fair honest test of powder temp stability one must actually shoot in the freezing cold conditions and not just stick the ammo in a cooler with dry ice.

A freezing cold rifle/barrel have a BIG effect on powder burn.

Once the outside temp hits -20 c ( -5 f ), ALL loads with ALL powders loose lots of steam.

I LOVE shooting in the freezing winter, and even tho ammo velocities plummet, for whatever reason they never go out of tune !!! I can't say the same thing about extreme hot temps.

 

[r bose]

LOL, yeah. . . I've never shot in 170° either, but have in 115° here in Arizona where it can get to 120°F. But. . . even if the ambient temperature isn't that high the temperatures inside a cartridge can sure get to be 170° if one has them sitting in the hot sun and/or in a hot interior of a vehicle OR in a hot chamber. For sure, they'd be really hot to handle at 170°F. Anyway, I make every effort to not do that.

Rookie mistake letting ammo sit in a hot car just before shooting them or letting a round cook in a chamber. Wait till you see your wind condition then close the bolt!!

 

[LVLAaron]

Interesting that AR Comp slows down until 75 degrees

 

[K22]

I hunt all year around, varmints (ghogs) in the spring / summer and predators in the fall / winter. After many years in the field I've noticed a few things regarding this issue.

1. I had trouble with ball powders, namely H380 in the 22-250 and H335 in the 223 in the summer when the temperatures were in the 90's. Had some pressure surges with otherwise stable loads in the fall and spring.

2. Even with so called temperature stable powders such as the Hodgdon extreme extruded series I'ce noticed some slight change in point of impact about 1/2 moa from approximately 80 / 70 degrees to 40 /30 but have not experienced any pressure surges with these powders. The change in POI may be due to the changes in air density not so much the affect of the temperature on the powder.

 

[Earnhardt]

To do a fair honest test of powder temp stability one must actually shoot in the freezing cold conditions and not just stick the ammo in a cooler with dry ice.

A freezing cold rifle/barrel have a BIG effect on powder burn.

Once the outside temp hits -20 c ( -5 f ), ALL loads with ALL powders loose lots of steam.

I LOVE shooting in the freezing winter, and even tho ammo velocities plummet, for whatever reason they never go out of tune !!! I can't say the same thing about extreme hot temps.

What's your definition of freezing winter? Mine is -40F
What's your definition of lots of steam? Mine is 50 fps loss...
Try RL-16 if your cartridge allows, or H322. Great powders for minimal fps loss over various temps.
Who cares what an article says...
Go shoot some yourself, and create your own data

 

[xswanted]

I hunt all year around, varmints (ghogs) in the spring / summer and predators in the fall / winter. After many years in the field I've noticed a few things regarding this issue.

1. I had trouble with ball powders, namely H380 in the 22-250 and H335 in the 223 in the summer when the temperatures were in the 90's. Had some pressure surges with otherwise stable loads in the fall and spring.

2. Even with so called temperature stable powders such as the Hodgdon extreme extruded series I'ce noticed some slight change in point of impact about 1/2 moa from approximately 80 / 70 degrees to 40 /30 but have not experienced any pressure surges with these powders. The change in POI may be due to the changes in air density not so much the affect of the temperature on the powder.

So this is my theory too. Even though I asked the question in the original post I’ve done quite a bit of informal testing in extreme cold.

I’ve let a rifle sit out overdid a few hours in -10 to -14 degree F. Shot the same load I’ve worked up in warmer temps and noted not a lot of change. For lack of argument sake I won’t make the powders I’ve done this with but I firmly believe cold dry air has more of a negative effect on velocity than does the temp when dealing with the 50 degrees below freezing.

One powder I will mention that has tested within 15fps of each other from mid 70s to -15 was IMR4350 in my 260.

I shot it last winter with the same load I worked up in the summer to find that it didn’t slow down much at all. Ammo and rifle were outside for quite some time prior to chronographing the load.

It’s an interesting topic to say the least.

 

[xswanted]

I will also add that I typically work a load up for the two rifles I coyote hunt with in the early spring or late fall so it’s cooler than summer. I shoot for the days that will be in the 20-30 degree F range.

I find this gives me a better idea of what I’ll have when it’s butt cold out.

The rifle I use for 0-350 yards i worry about a change in velocity less than I do about the rifle I use for shots or areas that I may see Shots stretch beyond 350 yards.

 

[Zero333]

What's your definition of freezing winter? Mine is -40F
What's your definition of lots of steam? Mine is 50 fps loss...
Try RL-16 if your cartridge allows, or H322. Great powders for minimal fps loss over various temps.
Who cares what an article says...
Go shoot some yourself, and create your own data

I have my own data and if I was talking about something I read somewhere, i would say so before hand.

Chronoed a 308win load with Varget.. It lost 82 fps in -25 Celsius ( -13 f ) compared to the velocity recorded in the summer at 28 c ( 82 f). But on the other hand It only lost 18 fps in -9 c ( + 15 f ) temp.

 

[urbanrifleman]

People still do not understand there are TWO independent factors effecting bullet speed.

Powder temp sensitivity
Ambient air density

Even with a powder of ZERO temp sensitivity, you will see approximately 1 fps of change per degree F. Colder goes slower. Higher temp goes faster.

Testing powder sensitivity must be done at a constant ambient temperature to isolate the variable.