Reloading in extreme temperatures spreads

[Ridgerunner griz]

I live in the interior Alaska where we can get -65 below zero to 85 degrees above. I have a new rifle 338 lupa mag just shooting Hornady factory 285 grain match ammo from -41 to 16 degrees I got an impact difference of 2.6 inches and group size spread of 1 3/16” more at 16 degrees. At -41 degrees I got 1/4 “ groups. I set rifle and ammo out on bench for 25 minutes before shooting.
I have been wanting to work up loads of 300 grain SMK and Accubonds I have Retumbo powder and IMR 7977, reloader 22.
So I called Hodgdon company and asked them what temperature spreads on retumbo they told me a 50 degree spread and that IMR 7977 was 100 degree spread. I also called Hornady they told me at the temperature spread I shot there factory load to expect a 30 percent change.
So it looks like to try to work up loads would be better at 30 degrees to be mid stream on the temperature.any input would help, I do not want to have too hot of a load in the higher outside temperatures.

 

[RTH1800]

With those extremes you might consider loading for two to 3 temp brackets. I normally work up my loads in the higher range of where they will be shot. But my range is -10-+90. It occasionally gets a bit hotter and colder here at times but I don’t shoot much in those extremes.

 

[Ridgerunner griz]

That’s where I’m trying to get is the higher velocity, but I can see that loading for different temps would be better but real costly in the workup. What part of the country do you live? I thank you for your input.

 

[Texasflyer]

I live in tx, about 70 above when i did my workup. I use 7977 and really like it. 91.0 grains pushing a 300 grain a tip running about 2700 consistently using wm primers out of a stock ruger rpr 338lm.

 

[RTH1800]

Welcome. Kansas.

 

[Ridgerunner griz]

Thank you for the load tips of 7977. Makes me wonder what the military snipers are doing about artic warfare loads?

 

[Ridgerunner griz]

What kind of brass are you using?

 

[Ridgerunner griz]

Welcome. Kansas.

Thank you

 

[918v]

You need a chrono and test it yourself rather than relying on hypothetical numbers someone pulls out of his ass.

 

[Texasflyer]

What kind of brass are you using?

I have some selllier and bellot, hornady, lapua and winchester. I havent shot the winchester yet, the lapua brass seems top notch and came new berger 300 grain match scenars. I bought about 100 rds of factory ammo when i got my rifle and have been seeing which i like out of the lot. With my current loadout at 3.646 coal they all seem really accurate. I have 13 loads on the sellier and bellot cases, and 6 on the hornady and 1 on the lapua so far.

 

[Ridgerunner griz]

I

You need a chrono and test it yourself rather than relying on hypothetical numbers someone pulls out of his ass.

use a chrono and start mid range on loading data and work up 2/10 of a grain at a time, I do not shoot anyone’s reloads

 

[918v]

Do a velocity ladder, take the second node and test frozen rounds vs hot rounds you heated inside.

 

[TheBoctor]

Develop a load in the summer when it's as hot as it's going to get and that'll make sure you're safe. Then when winter rolls around, throw some of those same loads over the chrono and take note of how the performance changes. Hopefully, velocity falls off a little but your ES/SD's stay low. If you've fallen out of the node, you can tinker and get back into it and set it aside for winter-only use, but be VERY CAREFUL because that winter max charge weight will likely be over-pressured in the summer heat.

 

[Slab74]

I may be stupid, but I am not shooting at -41.

 

[DIBBS]

I

use a chrono and start mid range on loading data and work up 2/10 of a grain at a time, I do not shoot anyone’s reloads

With that big of a case, I personally believe that you may be wasting precious components going up 2/10 of a grain at a time in load development. Personally I would use .5 grain steps and then when you have a load that appears good fine tune with smaller increments.

As another poster stated , either develop 2 loads, one for heat, one for cold, or develop your load in the warmest weather that you will shoot, and then chronograph and adjust your ballistics/trajectory when its really freeking cold.

 

[hafejd30]

The only numbers I’d be concerned with here is the flight number to get my ass some place where I don’t shoot in -41°

 

[Ridgerunner griz]

Hear in Alaska we hunt Caribou and some times moose in the winter months so that is why I’m shooting year round. Most of the time winter month hunting is back in on snow go so it is not like road hunting in a pickup and keeping everything warm. I thank you all for your input. I will be waiting for the warmer weather and start my load development.