Load testingin cold weather?

[DsrtRat]

I recently purchased a new gun and have been messing with some different loads. I have ballparked a load for 3 different bullets and have the new ones loaded and ready to go. My ballparks were all derived when the temp was +2 to +10degC. Going to be a no wind day tomorow morning but the temp is showing -12 for the morning.

Will that tempt swing affect my results? The loads are pre-made and I won;t be loading at the bench. Just curious if the temp will affect the pressures and or speeds much.

 

[Ryan500]

In my experiance it does affect things, I loaded up some with IMR 3031 and the good load in the winter was not so good in the spring. I think it is very dependant on the powder you use as some are affected by temps more that other.

 

[elkhuntr]

Likely to be slower, not a bad thing. But developing from cold to hot is another story. Where near max loads in winter any hotter weather may make thinks worse in the pressure department. The Hodgdon line powders appear to be more stable in temp swings than IMR, yet to be tested for me but others may chime in. Record everything if you are serious into target. For hunting....may not change much for you. Find your barrel's sweet spot and dont look back. A Chronograph is a great tool to verify this for your piece of mind.
Elky

 

[mmattockx]

Will that tempt swing affect my results? The loads are pre-made and I won;t be loading at the bench. Just curious if the temp will affect the pressures and or speeds much.

I would expect to see some differences. I have loads that leave slightly flattened primers in summer and nothing in cooler fall temps. I also found that I needed to bump my charge weight a bit to stay on the accuracy node from summer to fall. In my 6.5x55, 47.8gr of RL-22 and 140gr SST's was the node in summer, but I had to bump to 48.0gr of powder when temps got down towards freezing.

Mark

 

[CyaN1de]

It will depend mostly on the powder you used.

Some powders (such as Hodgdon Extreme powders) are more temperature stable than others.

I shot the same (winning) load from early spring (+5-10C) when I developed it, during the summer at +30C, right into -20C temps last winter with no change in accuracy using Hodgdon Varget....YMMV

 

[DsrtRat]

Thanks guys. I am shooting Varget in a .223 REM. I am revisting some intial loads that I did and starting at the last "scatter" group and working my way up slowly. Hopefully I will work into that sweet spot regardless of temps.

 

[Ron AKA]

Thanks guys. I am shooting Varget in a .223 REM. I am revisting some intial loads that I did and starting at the last "scatter" group and working my way up slowly. Hopefully I will work into that sweet spot regardless of temps.

Varget is one of the Hodgdon Extreme powders and is fairly temperature insensitive. It still does slow down some with a temperature drop. Another member here, kombayotch, I believe has some good data on how sensitive it is. You may want to PM and ask for a post of his graphs. They are very informative.

But, you are probably not wasting your time testing in cold weather with Varget.

 

[Northman999]

I always assume there will be a difference, essentially that hotter summer weather will mean increased pressure.

When I am working up loads in the winter I generally keep my ammo in the front seat of the car with the car running and the heat on (so it's about +20 celcius in the car) and only take small batches of ammo with me to the bench - these rounds I keep in my inside pocket and load single rounds from there. So far this has let me develop loads in the winter that are also safe for summer use.

I'm certain that if I developed some max pressure loads at -20 and then took them out a +20, I'd likely run into trouble otherwise...

 

[DsrtRat]

All good info guys. Can someone explain the science behind the same amount of powder being a hotter load in the summer? My loads were are weighed indoors at my house. What causes that same combo to be so much hotter in the summer?

 

[stubblejumper]

All good info guys. Can someone explain the science behind the same amount of powder being a hotter load in the summer? My loads were are weighed indoors at my house. What causes that same combo to be so much hotter in the summer?

The burning rate of the powder changes with temperature.

 

[DsrtRat]

Ahhhh, right. Never thought of that.

I guess I will find out today. Going to be around -10C so I am looking at 12-20deg shift. Maybe with the varget, things won't be too drastic.

 

[H4831]

A waaaaay too much is made of temperature changes in shooting. Just go out and shoot.
I grew up in a very cold part of our boondocks where bush homesteaders, trappers and anyone else, shot big game year around for food. They hunted when it was 40 degrees below zero. Of course, every one used factory loads, so they just went out in the severe cold with their 30-30s and killed moose.
Unless you are going into a super match competition, and maybe even then, just disregard the temperature, and shoot.
OK, I hear the shouts. build up your load in cold weather, then go out in July with it and the gun "blows up in your face." If you loaded in cold weather to where it was on the verge of all the rifle could stand for pressure, this may be true. But most of us just use normal loadings. And there is a big margin of safety, before the bolt even starts to stick.