temperature variation

[cbourbeau32]

I am loading my 243 and 7mm 08 with H-414 and H-380 and have read about various powders having temperature variations or being temperature sensitive. Does anyone know how extreme these two powders are? I will be shooting soon with temps likely in the 90's when I sight in. Hunting season is usually low end 30's and high end 50's. Will this make a noticeable difference? Any advice would be appreciated. Thanks, Charlie

[quickdtoo]

They aren't listed as Extreme powders by Hodgdon, which are supposed to be less sensitive to temp swings. The only way to know how they're affected by temp is to shoot them. Put some of your loads in a cooler to chill them good and head to the range to compare them.

Tim

http://www.hodgdon.com/smokeless/extreme/page4.php

[Graybeard]

Temperature sensitivity as an issue is GROSSLY over rated really. Unless you're developing your loads in sub freezing and especially sub zero temperatures and firing them in the high 90s to over 100 degree temps or vice versa it's really not that big a deal. Some say sub zero temps will lower velocity a wee bit and it might and for sure the well over 100 degree temps will slightly raise pressures. But really how often do you use it in such extremes?

If your normal use patterns are in temps from above zero to under 100 degrees it's really not worth worrying yourself over.

[Freezer]

    Varget is supposed to be a powder that is not temp sensitive.  BTW it works great in my 308. 

[cbourbeau32]

Thanks all. I figured that would be the answer. Charlie

[Siskiyou]

H-414 is my favorite powder with 80 grain bullets in the .243 for varmint hunting.  I have not notice any point of critter shift of accuracy; be the target a coyote or a digger squirrel. I also loaded H 414 in the 30-06 and fired it in hot, and cold weather without a problem.

It was not until they came out with the Extreme powder that I realized I missed the first shot on that Colorado buck because the temperature was ten below zero.  I had to make a slight adjustment and knock the ice icicles out of my mustache before I connected on the second shot. 

[Questor]

In my case, I develop loads during winter then use them during summer. For that reason I like the Hodgdon Extreme powders because I am sure that I don't need to worry about pressure problems introduced through higher temperatures.  Your situation is the opposite, where any changes will be to a lower pressure and velocity because it's getting cooler. 

Since you'll be re-zeroing just prior to your big game hunt in cooler weather, the temperature variation question isn't very important to you.

I've used some powders, like Winchester 748, and the difference in a bottleneck cartridge loaded in winter (20F) and shot in summer (95F) can be a 200fps. Even relatively low pressure cartridges like 6.5JDJ will vary by 150fps using big game bullets. For long shots at small targets this difference can lead to perplexing misses unless you re-zero.

[jhalcott]

  Beau, one year I was laid off in January, so I worked up some ground hog loads thru April. When I shot those loads in july and August, I had to keep the GUN and ammo in the shade. If I let either get too warm, I'd get a sticky bolt. Primers would also swell to much. I never had a BAD prioblem,but maybe I'm lucky. These were MAX loads but VERY accurate. NOW I'm a bit skittish of that stuff.

[Graybeard]

  Beau, one year I was laid off in January, so I worked up some ground hog loads thru April. When I shot those loads in july and August, I had to keep the GUN and ammo in the shade. If I let either get too warm, I'd get a sticky bolt. Primers would also swell to much. I never had a BAD prioblem,but maybe I'm lucky. These were MAX loads but VERY accurate. NOW I'm a bit skittish of that stuff.

Nope Jay I suspect those were WAY over MAX loads and you only got away with it during cold weather but even then I'll bet the pressures were at least 10,000-15,000 PSI too high.

[jhalcott]

  Yes GB ,I agree. back then I was TOO smart to BUY a chrono. Those loads worked SOO well in winter I just had to use them. I had a REALLY sticky bolt in a new field and had to use a lot of force to get the action open. I used my alternate gun the rest of that day. I pulled the bullets and weighed the charges thinking I MAY have made a mistake when loading them. NOPE, the scale read what the label said. I tried to convince myself that jostling the ammo around in the Jeep affected the powder. Of course I knew better,but I was 10' tall and bullet proof !  I gotta be crazy! one of my friends got one of those piezo electric strain gauges. My FIRST THOUGHT was load a couple of the "summer" loads and test them !!??  I didn't and wouldn't!

[MnMike]

I tend to develop deer loads in the summer. I found a great load for my 7-30 Contender using Win 748. A couple of weeks before deer season it was a little cold (-2) , and I fired a few rounds. Bad groups. I had done a load with Varget, not great, but OK (1 1/2") so I switched to that. It still shot 1 1/2".

Just my experience,

mike