Temperature affects

[sty]

So I was sitting in my deer stand today and started the think...witch is never a good idea but anyway here is my question.
If you load rifle rounds up in the summer and get it all to your liking, how much does the temperature affect your load?
I have not loaded for rifle yet so I was thinking if I work up a load at say 70° and now come deer hunting and it's 10° out what is the affect.
Does temp change make pressure and FPS go up or down?
I don't shoot very far deer hunting (150 yds. Or less) but this just popped in my head and I would like to know.

[AllenJ]

We had the same discussion not long ago, here is the link:

http://thefiringline.com/forums/showthread.php?t=536583

[sty]

I must have missed that one. Thanks

[Mike / Tx]

The ONLY time I have found issue with a load was when I was packing a compressed load of RL-22 in a 30-06. Temps above 50 up to around 101, it shot fine no issues. Sitting in the stand one morning when it was close to 25 with a VERY stiff north wind adding to that, when the trigger was pulled they went off, but they impacted out about 250yds instead of the 380'ish I was shooting them to. Not only did they fall short once, but thinking something had to be wrong I tried it again and got the same results. Just wouldn't light it all off properly with the low temp. However the same exact powder form the same can worked just fine in my standard load from my 25-06 several minutes later, resulting in venison on the ground.

SO as long as your not loading a fairly compressed load of slow burning powder lit with standard primers you should be fine.

[Jeff2131]

Depending on the caliber and load you are using, magnum primers may be a better choice for extremely cold weather applications. Standard primers may not properly ignite a large or even compressed load enough to get the accuracy and reliability you got when the temps were up.

[sty]

Would it be better to just work up loads in the temps that are close to when I would be using them?

[Bart B.]

Safe loads worked up in 80 deg temperatures will typically shoot to the same point of aim within 1/2 MOA for the first 400 to 500 yards in 20 deg ones.

The ammo's zero obtained in 80 degree temps wearing light clothing may well change when you're bundled up in heavy clothes at 20 degrees. The resistance to the rifle's recoil during the time the bullet's going down the barrel has changed.

If the very best accuracy and zeros are important, it's best to work up loads and get zeros with them in the environment they'll be used in. That includes location, weather and dress; all's part of the environment.

[sty]

That is one thing I have learned over the years is getting the scope in the right stop with the clothes I will be warring. The hold on the rifle is so different sitting on a bench in the summer that in a tree or standing all bundled up.

[arizona98tj]

You can use one of the shooting apps to experiment with "what ifs" in regards to temperature and air density effects on trajectory. If you can get temp data from the manufacturer, some apps allow you to plug in that variable as well.