plastic flow of primer material

[old_heli_logger]

Some powders vary more than 1fps per degree of temperature change. Some are less than .01 per degree.

This chart shows the fps change vs temp change for some powders.
Hope this helps

 

[memtb]

This chart shows the fps change vs temp change for some powders.
Hope this helps

But yet, I think that under certain specific circumstances this may not be entirely relevant!

Example: Several years ago there was a lot of discussion about the temperature sensitivity of RL 17…..which I use in my 375 AI.

I do my load development in warm to hot conditions, so with all of the conversation…..I picked a cool day to test my load!

During testing the temperatures ran from a -3 to a -4 F. I allowed the rifle and the cartridges to reach ambient, then ran 3 rounds across my chrono

I actually showed a velocity gain of 8 fps (99% certain of the 8 fps), and got a pretty darn respectable 300 yard, 3 shot group!

Perhaps mine was an anomaly……never to be repeated again! memtb

 

[old_heli_logger]

But yet, I think that under certain specific circumstances this may not be entirely relevant!

Example: Several years ago there was a lot of discussion about the temperature sensitivity of RL 17…..which I use in my 375 AI.

I do my load development in warm to hot conditions, so with all of the conversation…..I picked a cool day to test my load!

During testing the temperatures ran from a -3 to a -4 F. I allowed the rifle and the cartridges to reach ambient, then ran 3 rounds across my chrono

I actually showed a velocity gain of 8 fps (99% certain of the 8 fps), and got a pretty darn respectable 300 yard, 3 shot group!

Perhaps mine was an anomaly……never to be repeated again! memtb

I agree with you that these numbers on this chart probably don't apply the same in all cartridges, but it gives us something for comparison for powder choices

 

[Mike Matteson]

This chart shows the fps change vs temp change for some powders.
Hope this helps

I have that! Thanks I think is show better that the one I download. So I download it. I'll compare. The only thing is I wish they would complete or somebody complete all the powder Temp rate change.

 

[Noobie]

This chart shows the fps change vs temp change for some powders.
Hope this helps

Thanks for the chart. The other factor that can help accuracy is low ES and SD (extreme velocity spread and standard deviation).

 

[Mike Matteson]

I have been talking about this for a long time on temp sensitive powders. All powders velocity change with the temperature changes. Some far greater than others. It's more so with longer range shooters. 50fps can change your POI as much as 14" @ 1000yds. Some of us hunt in weather that varies as much as 130' between high and low temps. Depending on what powder you are using that can be over 130fps change or it could be only 10fps. The other is your powder load can go from safe to over pressure depending on what powder is being used. When the powder load was figured out for your rifle is it done in cold weather mid temp or hot temps.
Now I will say I load hot, but no rejector marks or creator primers. Primers are flat, but that where I stop. Most of my load work up is during means temps. There is powder that don't change much in temperature change. I might not get the velocity that can be achieve with other powders, but at the same time I don't have to worry where my POI is going to be.

 

[highfinblue]

All the powder I shoot distance with is supposed to be insensitive to temps, and I believe it has helped me tremendously as I have not had trouble making shots out to 980 on game. I will not shoot if the wind is blowing much at all, but with all our practice I'm comfortable that my rifles are going to hit where they're dialed to out to 1000.

 

[ResearchinStuff]

I have been reading this post with interest. I bought a CA 7MM PRC this spring. When breaking in the barrel with factry Hornady 175 gr. edl-x and 180 gr. edl-m, almost all my brass showed signs of pressure. Brass had flatten primers and ejector marks, some worse than others. I just recieved new Peterson match brass to start load testing, not wanting to try reloading cheap soft Hornady brass from factry loads.

That's just because CA can't cut a chamber to spec, especially not a PRX chamber.

 

[Noobie]

My buddy had a box of factory ammo and he was shooting a semi-auto that was tried and proven to work well. This particular brass was from a respectable company but most of the primers had fallen out when he went to pick up the brass. Can't quite recall the brand.