Temperature Sensitivity with falling temps.

[Terry]

We hear a lot about temperature sensitivity with temps moving up. Any data on temps 30-50 degrees?

 

[Prose]

My working theory that I've been testing for a couple years is that the temp insensitive powders fall off when it gets cold worse than normal powders. The ones that "spike" when it gets hot maintain their speed when it gets cold. RL17 being my main test subject. My 260 Rem load of H4350 gets about 2820 FPS at 70°, but dips down to 2650 at 0° (that's a big difference). Same with RL16. But with RL17 I don't hardly lose anything.

 

[johara1]

A 6Br imp. from 60 degrees-40 degrees, 4350, 4895 and Varget loose 1 fps. per degree..... real world, gun and shells at the same temp. as tested..... jim

 

[Dusty Stevens]

^ precisely why you cant work up a load for a whole season. Changes every hour

 

[johara1]

between 60 and up to 85 they are ok, but at each end of that it goes to hell in a hand basket.i don't think I ever saw one long range shooter except for one trying to load at the range and it was a national with 10 or 12 relays. You sure don't have time if you are in the shoot offs.You sure can't drag your GD 503 down to the match and load...... jim

 

[Rob01]

I have shot both Varget and H4350 from single digits to over 100 degrees and got maybe a 20fps swing. Why I use them in my match rifles.

 

[K22]

I shoot (range time) and hunt all year around, varmints in the summer and predators / deer in the fall and winter months.

For sure, there is a difference between ball powders and stick powders in my experience with regards to temperature sensitivity and changes to point of impact.

But even with the "so called temperature resistance" powders I've experienced anywhere from a 1/2 to 3/4 moa point of impact changes from summer to winter depending on the cartridge. While some of this may indeed be due to the temperature affect on the powder's performance, I think some of it's due to the changes in air density between warm/ hot summer days to cool/cold fall and winter days.

For the ranges that I typically shoot big game this has no affect but varmints and predators it's a difference matter so I check point of impact for changes during seasonal changes. Through experience I now have a fairly good idea when adjustments are needed.