summer vs winter

[Rick223]

Ok heres a ?
Ive been advised that workin up a load in summer will shoot quite different in the winter, how much difference does temp make when you do this, I can see the first shot but what about after that when the barrel warms up?Is it a bad idea to try new loads in the summer months and expect them to perform the same when it gets cold?

Rich

[Hawks Feather]

While I have never gone to the bench in the snow, there was a slight difference in my group when it was cold.  But then shivering does tend to throw off the accuracy.  It was not enough that I would have missed a groundhog, but I probably would have shot for the center of the hog, behind the front legs, and not have tried a head shot.

Jerry 

[coyotehunter_1]

Rich,
Yep, some types of smokeless powders are more temperature sensitive than others. Although various powders can react somewhat differently due to temperature changes it should not make a major difference in accuracy.... unless your talking extreme variations. In these situations I'm more concerned about the possibility of excessive chamber pressure when using near max or max loads and temperature sensitive powders.   

Hodgon has developed a line of powders that they call Extreme Rifle Powders.

More on the subject:
   
http://www.hodgdon.com/smokeless/extreme/page2.php#top

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


 

[Ridge Runner]

all powders are tempature sensative, some more than others, with ball powders being the worst mainly due to a higher graphite content and the fact that unless loaded to max pressures they tend to run dirty.  I load for a wildcat called the 7mm Allen Mag, my standard load is 110 gr of wc872 (mil ball powder designed for the 20 mm vulcan cannon) this load runs 3500 fps with a 160 nosler at 50 degrees and under, at 70 degrees the load clocks 3680 and has a heavy bolt lift, at 80 degrees the bolt wont open, for warmer weather shooting I load 105 gr. Its a pain but the powder is 5 bucks a pound and the high graphite content is easier on the throat.
RR

[cb223]

Ridge Runner,  That is interesting! I know that powders are temp sensitive but 30 degrees and almost 200 FPS. I never knew they could be that sensitive!

[Ridge Runner]

yep, the WC872 is, I've saw over 100 fps variation from leaving a round set in a warm chamber while I change targets. in 30 degree weather the ES on that rifle is around 7 fps, you get above 80 degrees and the first shot has a heavy bolt lift, the second round you have to cool it down to get the bolt open.
RR

[vvarmitr]

This is an issue that has come more to light w/ Prarie Dog hunting. Guys would work up loads for a rifle during the off season (winter) then get out on the plains, have their ammo out in the sun & experience pressure problems. As in Ridge Runner case.
Accuracy was more of a problem of guns fickle of pressure.  Properly sit up guns w/ free floating barrels & bedded are often not as subject to the problems ... there are exceptions to the rules of course.

Hope my 2 cents help. 

[Ridge Runner]

well, you guys who have never dealt with ball powders like the wc872 and have doubts, let me say this, everything I've told you is what I've winessed while developeing a good long range hunting load for my 7mm Allen mag. In 30 degree weather it'll do 3670 fps with 115 gr of the wc872, I stick with 110 gr loads to give me a buffer for tempature swings during november while deer hunting. the 115 gr load burns clean as a pin at 30 degrees so I know that load is pushing right at 60k psi, the 110 gr load is just a bit sooty, so its close to 55k psi. in hot weather the 105 gr load (all these figures are with lapua cases and 160 gr noslers) is about the same pressure as the 110 gr load. Most of the long range hunters who use the 872 know that its best in cold weather and alot of the 1000 yd benchrest guys use it in the wintertime.
in most cases temp sen. powders do not behave so extreme but we're talking about loads of significately over 100 gr with this powder, and bullets that are at the hevier side of the spectrum for caliber. with all the shooting I've done with it I have pierced one primer, and have yet to enlarge a pocket enough to render the case useless.
RR

[Mallardsr]

Around 1983-84, I did quite a bit of reloading for three different long guns in .243. I had declared war on ground hogs and the targets were many. We were just starting to see coyotes  here in mid Tn. and the ground hogs were booming. Through uncounted hours of reloading and shooting I developed a compressed load with a powder called Hogden H450. The load had very little variance in fps and temp, although I'm sure affected it some, gave no real changes. The H450 was soon changed and 20 years later has apparently been dropped by Hogden. However the H380 looks like something I would have to try if I ever get time. RP