Per my other post, how much does the temperature differences summer to winter play in accuracy, POI, and all. Will the same powders group just as tight, just at different POI or will groups vary. I am trying to work up loads for 22-250 and 223 for a p-dog hunt. Won't be no -15 degree's when I'm out their! Want to start loading up and working up loads though. I'm using Varget, H380, and IMR4064. Thanks!

I tell ya one thing. I made up this nice accurate load last winter in 20 degree weather with a 180gr trophy bonded with Re22 in my 300RUM. shot it in the summer and it locked the brass up in my gun. Yes, you might have to readjust a tad your loads in extreme weathers, for example 6 degrees vs. 90 degrees.

If you work up max loads when it is cold you will need to tweak them when it gets hot. Appx 100fps to 200fps will be the appx. difference for the powders you listed.

If you work up max loads when it is hot they will be somewhat less potent when it gets cold, to the same extent inversely.

I have seen charts on the difference on the net somewhere but cannot recall the site. I think it was on a sniper site I found by doing a search on long range shooting.

The Hodgden Extreme powders are not supposed to have quite as large a pressure variation due to temperature as some other powders.
I normally reduce my loads by 1 grain from cold to hot temps using Hodgden H4831.

Thanks, I'd heard that about the hodgdens as well. I'm not loading to max, so Pressure is problebly my second concern as apposed to accuracy. To my thinking, this shouldnt vary, should it?

first time,
it may vary a little bit.
I know when I am working up a load the accuracy will vary when I put in a couple grains more or less powder and change the velocity accordingly.

You will need to shoot in the appx. temperatures you will be hunting in to fix your final sight in before you go hunting.

For longer range shots (over 300 yards) there will be definite difference in accuracy. The bullets impact on the target will impact higher or lower depending on the velocity changes. There will also be a slight difference in wind drift, again more noticeable at longer ranges.

Go to one of the ballistic information sites on the web and punch in your info and it will give you a readout on what happens when the velocity changes.
Go to www.biggameinfo.com.
Really cool site. Has a ballistics calculator, recoil calculator and some other cool stuff.

Thanks. I was hoping to work up some loads this winter. Doesn't sound so good for that huh?

Thinking a little more on this, I'm maybe not explaining really well. What I really wondering is if I load the most accurate (read: tightest groups) load at 10 degrees, will it still be the most accurate grouping load at say 80 degrees. I have no problem adjusting the scope later!

FTEK,
Carl W. Johnson,Jr. wrote a detailed account of tests of this that he had made.
I read it in the American Rifleman.
It concerns cast bullets with Dacron or Kapok fillers,but,to some extent,it will pertain to jacketed bullets.
It was an extensive test,using 4 different rifles and 2 different calibers.
He used 2 different powders and 2 different bullets.
The groups that he got at 60-70 degrees were different then those at 70-80 degrees,and very different then those at 80-90 degrees.
Not only was the POI different,but the group size was different.
After reading this,I took my Springfield Krag to the range in 30-40 degree weather to check out the loads that were chronographed at 75 degrees.
I'm sorry.I forget the reading,but it was signifigant. My next hunting load will be loaded over max,because my regular load is at max. I will mark the ammo for Hunting only.(I've been shooting the same load for twenty years)It's a jacketed bullet load.
Frank

first time,
I don't drive myself crazy about it.
I do all my load development and long range shooting practice in the spring after coyote hunting is over.
One reason is that I am not so busy that time of year.
But mainly because it is cold enough that the barrel does not get so hot.
I can do a good range session in the spring in an hour.
In the summer it takes a least twice that long unless I want to run the air conditioner in the truck to cool the barrel between groups.

I don't let my barrel cool between shots because I want to see what the load will do in the field. I let it cool between groups though. Never more than 3 shot groups or it gets too hot.

I choose the bullet I want to use for the game application.
I then experiment with powders to get the best accuracy/velocity combination I can. Then unless the groups are over 1" that is the load I use for hunting.
My rifle is very accurate so I have never had a hunting bullet I couldn't get to group under an inch with some combination.

Where I live the fall temperatures when I hunt are basically the same as the spring temperatures.
For shooting in the summer put in a grain or two less depending on how hot it is and go for it. However as I said I do the vast majority of my load development and practicing in the spring when it is cool, 30-50 degrees is my favorite temp to shoot in. I also try to always use one of the Hodgden Extreme powders such as H4831 for all my loads. They have much less temperature/pressure variation than some other powder.

Good response, thanks

I just read some literature from hodgden that says that Varget only had 4fps difference b/t 0 degrees and 125 dergees! Think thats my powder!