Temperature sensative loads

[LaHunter]

I have developed a very accurate load for my 7mm Rem mag. I am using 64.3 grains of IMR 4350 powder shooting 150 grain Nosler Ballistic Tip bullets at 3200 fps at 55 degrees F as per chrono set at 14 ft from muzzle.

Recently I was at the range with the same hand loads and the same set up, except the ambient temperature was 80 degrees F. I was seeing velocities of 3255 fps with the same chrono set at the same distance from the muzzle. Extreme spread was about 17 fps during this range session which is typical.

This is the first time I have fired this rifle with this ammo at a temp above 55-60 degrees F.

Will a 25 degree increase in temp usually result in a velocity gain like I am seeing with IMR 4350?

Would you consider these results to indicate IMR 4350 is temperature sensitive or not? I am fairly new to loading my own ammo so not sure what constitutes "temp sensitive powder".

I understand that it is an increase of only 1.7%, but it is 55 fps more. Accuracy was still fine, just want to understand what I am seeing.

Any thoughts and input are appreciated.

 

[kcebcj]

All powder is temperature sensitive some more than others. I develop all my hunting stuff in the spring and fall like now when the temps are within 20 degrees of what I hunt in. Most of the loads developed like this usually end up a couple grains below what Quickload deems dangerous so if I shoot them when its warm I don't need to worry about having a problem and if they shoot a little off I understand why.

One powder that I have fooled with that was pretty good whether hot or cold and accurate is H4831. Just could not get the velocity out of it that I was after.

You also have to understand the consumer chronographs are not perfect. I use the Ced M2 and at times I just shrug and ignore the data. Your real fps will become evident when you prove the come ups and make the corrections in your ballistic program.

Yes a temp swing can really mess with the load. Just letting the loads sit in the sun will have a impact.

 

[MagnumManiac]

I do all of my load work up in hot weather, it may be uncomfortable shooting in such weather, but it's the only way to see max loads in the temps I hunt in. I don't always hunt in these temps, but the velocity difference, if any, between hot weather and cool weather is neglible in 90% of hunting.
For true long range work, I run the same loads in hot and cold weather, but I check what velocity I'm getting in the field and adjust my dope if necessary.
Yes, I would say that all IMR powders are temp sensitive, some more than others.
Hogdgon Extreme powders are what you need for temp stable powders.

Cheers.
gun)

 

[tbrice23]

Imr4350 gm210m 162amax
All 60.8gr

18 deg f.= 2949fps sd =10
30 deg f.= 2940fps sd =16
64 deg f.= 2949fps sd =9

read your post and got me thinking. So here is my actual load notes on the same load.

 

[tbrice23]

However ive heard 75 to 80 deg is the point where some guys see pressure spikes. I know reloader22 is only shot in my 300wm under 50 deg.

 

[No Fear in Accuracy]

If you plan to hunt in cooler season, you can put the bullets in the cooler lunch box with blue ice. Bring it to the range and load it while it is cool.
The temp sensitive will be pretty close when you hunt in colder climate.

 

[tbrice23]

I always wonder how much condensation builds up on the inside walls of the case and if thats why my accuracy was poor when I tried the ice cooler thing?

 

[No Fear in Accuracy]

Use Zip Loc bag with the bullets inside.

I'm not sure about the condensation builds up. In Alaska or in Canada, the cabin was cozy warm and the bullets were inside the cabin all night then went out of the door in the morning with the minus 5C or 25F.
I'm not sure if it will affect the accuracy?

 

[gillettehunter]

One other question for the OP. Was the powder all from the same can? Sometimes lots vary some...... Bruce

 

[LaHunter]

The powder was from the same can. Brass was all prepped the same, loading process was the same, bullets from same box, etc. The only variable that I can i.d. that changed was the ambient temp increase of about 25 degrees.

Thanks for input