How do you consider powder temperature sensitivity when developing load data?

ttk9801

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Every type of powder may have different temperature sensitivity and some are more sensitive to temperature change than others. The muzzle velocity can vary noticeably especially considering a temperature change such as from 20 F degrees in the winder to 95 F degrees in the summer.

If you developed a maximum load in a 20 F degrees winter condition using a temperature sensitive powder, is it true that it may be too hot a load (therefore it may be unsafe) for 95 F degrees summer condition? Even for loads that you think are safe, the velocity can vary a lot and therefore the grouping/accuracy may change such that the best load data developed in winder may not be a good data for summer conditions.

I had compared two of my tests of .223 rem. A 22 F degrees drop (from 42 F to 20 F) resulted in a 155fps drop in muzzle velocity. This is 23gr IMR 4895 with 55 gr FMJ from a 1/12 twist rate Rem 700 SPS 26” .223 rem rifle. The 155fps drop seems too much to believe but that was what I got.

I am curious how you guys modify your load data over different seasons (temperature conditions).

Thank you in advance for any info.
 
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Every type of powder may have different temperature sensitivity and some are more sensitive to temperature change than others. The muzzle velocity can vary noticeably especially considering a temperature change such as from 20 F degrees in the winder to 95 F degrees in the summer.

If you developed a maximum load in a 20 F degrees winter condition using a temperature sensitive powder, is it true that it may be too hot a load (therefore it may be unsafe) for 95 F degrees summer condition? Even for loads that you think are safe, the velocity can vary a lot and therefore the grouping/accuracy may change such that the best load data developed in winder may not be a good data for summer conditions.

I had compared two of my tests of .223 rem. A 22 F degrees drop (from 42 F to 20 F) resulted in a 155fps drop in muzzle velocity. This is 23gr IMR 4895 with 55 gr FMJ from a 1/12 twist rate Rem 700 SPS 26” .223 rem rifle. The 155fps drop seems too much to believe but that was what I got.

I am curious how you guys modify your load data in difference seasons (temperature conditions).

Thank you in advance for any info.
Interesting, I never really gave it much thought. There are some with a lot of experience here, they’ll surely have run across this situation.
 
Every type of powder may have different temperature sensitivity and some are more sensitive to temperature change than others. The muzzle velocity can vary noticeably especially considering a temperature change such as from 20 F degrees in the winder to 95 F degrees in the summer.

If you developed a maximum load in a 20 F degrees winter condition using a temperature sensitive powder, is it true that it may be too hot a load (therefore it may be unsafe) for 95 F degrees summer condition? Even for loads that you think are safe, the velocity can vary a lot and therefore the grouping/accuracy may change such that the best load data developed in winder may not be a good data for summer conditions.

I had compared two of my tests of .223 rem. A 22 F degrees drop (from 42 F to 20 F) resulted in a 155fps drop in muzzle velocity. This is 23gr IMR 4895 with 55 gr FMJ from a 1/12 twist rate Rem 700 SPS 26” .223 rem rifle. The 155fps drop seems too much to believe but that was what I got.

I am curious how you guys modify your load data in difference seasons (temperature conditions).

Thank you in advance for any

Once I found out tomorrow will be 55 in boston, I will be heading out for load development myself.
From my understanding, might have to deduct a few grains in the summer . My node is over max from Berger, but no signs of excessive pressure.
 
Yes, it's true. I don't push maximums to begin with because maximum loads aren't usually the most accurate in my guns. That gives me some cushion. Fun fact: WInchester WST is reported to be reverse temperature sensitive.
 
Yes, it's true. I don't push maximums to begin with because maximum loads aren't usually the most accurate in my guns. That gives me some cushion. Fun fact: WInchester WST is reported to be reverse temperature sensitive.

Maybe mixing Win. WST and IMR 4895 would get a mix that has the same burn rate at all temperatures. Like those rigs made of different metals in clock pendulums to keep the pendulum length (and therefore its period) the same between winter and summer.

I’m kidding, of course. I’d never mix powders. And if it were easy (or possible) a powder manufacturer would have done it already.
 
Maybe mixing Win. WST and IMR 4895 would get a mix that has the same burn rate at all temperatures. Like those rigs made of different metals in clock pendulums to keep the pendulum length (and therefore its period) the same between winter and summer.

I’m kidding, of course. I’d never mix powders. And if it were easy (or possible) a powder manufacturer would have done it already.
Might be the same burn rate: BOOM.

Some powders are advertised to be less sensitive. I think Vihtavuori generally claims to be. Winchester StaBALL Match is another. That might be good for 223.
 
Yes, it's true. I don't push maximums to begin with because maximum loads aren't usually the most accurate in my guns. That gives me some cushion. Fun fact: WInchester WST is reported to be reverse temperature sensitive.
this. And yes WST is reverse temp sensitive. I picked up a pound a few months ago and have been meaning to try it for some super soft 9mm loads.
For rifle calibers I’m usually between mid-max charge weights. If I knew I was loading close to max (with a standard temp sensitive powder) I’d try to do the testing in the summer.
 
Every type of powder may have different temperature sensitivity and some are more sensitive to temperature change than others. The muzzle velocity can vary noticeably especially considering a temperature change such as from 20 F degrees in the winder to 95 F degrees in the summer.

If you developed a maximum load in a 20 F degrees winter condition using a temperature sensitive powder, is it true that it may be too hot a load (therefore it may be unsafe) for 95 F degrees summer condition? Even for loads that you think are safe, the velocity can vary a lot and therefore the grouping/accuracy may change such that the best load data developed in winder may not be a good data for summer conditions.

I had compared two of my tests of .223 rem. A 22 F degrees drop (from 42 F to 20 F) resulted in a 155fps drop in muzzle velocity. This is 23gr IMR 4895 with 55 gr FMJ from a 1/12 twist rate Rem 700 SPS 26” .223 rem rifle. The 155fps drop seems too much to believe but that was what I got.

I am curious how you guys modify your load data over different seasons (temperature conditions).

Thank you in advance for any info.
I dont think 20’ to 95’ will affect chamber pressure enough to be dangerous. I just cant see powder manufactures putting out a powder that sensitive?

All though I am sure you will see changes in velocity especially at extreme temps like negative temps and say ammo sitting in your trunk on a 100’ plus day

Plus how hot does a round get sitting in a nice warm chamber

What you need to do is check the performance of your load through out temp ranges.
 
W748 is not a temp stable powder. Love this powder, but this is the one issue. I have developed a lot of charge wt. data to compensate for shooting in the hot summer months and the colder fall.
 
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