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Old October 11, 2012, 10:44 PM   #1
Join Date: December 27, 2009
Posts: 23
Temperature changes, and accuracy...

New to reloading here, and just heard today that temperature differences will effect accuracy. Does this mean that all the work I did in the summer on my 308, 30-06, and 45-70, is for nothing. I reload for hunting, and have all three loads and rifles right where I need them. Any input is appreciated.
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Old October 11, 2012, 11:10 PM   #2
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It shouldn't affect accuracy much, but depending on your powder, it can significantly affect POI (Point Of Impact). You might have a .5" group perfectly centered on the bulls at 85f, and then you shoot at 35f, your .5" group will be low....

The reason is velocity. Many powders will have major velocity differences at different temperatures, high temps will cause velocity to go up, while lower temps will be opposite....

If possible, zero your rifle as close to the temp you plan to shoot as possible....

Also, some powders are much less temp sensitive than others. Hodgdon "extreme" powders at made to have very little velocity change with temp swings... I use Varget, which is an extreme powder, and develop my loads in the summer, then when I do my final sight in just before the hunt, I have not noticed any significant accuracy or POI change.
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Old October 13, 2012, 11:26 PM   #3
Marco Califo
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Join Date: April 4, 2011
Location: LA
Posts: 1,251
Beware marketing myths

Accurate Powders Answer: "Most of our powders are not insensitive, and will show some effect at hot and cold temperatures.

However, we test at -40F and +125F and the deviation in most cases are ca 3% to 5% at these extreme levels. Therefore most shooters do not notice much difference under normal practical hunting conditions.

More elaboration on the subject:

Complete temperature stability can only be achieved with tubular extruded powders designs, either with double base (NG) and/or with other coating technologies.

Because the ballistic performance at extreme temperature is completely dependant on the specific combination, it is very difficult to quantify and qualify.

Our standard powders perform very well at extreme temperatures, and usually pass the strict military requirements by a large margin.

This is a subject that often fraught with misconceptions and inaccuracies.

The term is used loosely by manufacturers without qualifying the subject, and is obviously exploited for marketing purposes and perceptions.

The facts are:

Although powders can be improved, it’s really only possible with advanced coating procedures and additives which increase the cost.
A particular powder can be improved re temperature stability for certain combinations, within a certain envelope which is specific to the following three main parameters/aspects
The caliber.
The weight of the projectile/bullet.
The performance level.
If any of these parameters/aspects go beyond or outside the intended ratio/s, the results will change and the performance will sometimes be different.

It is also very important that when a comparison is made, that all conditions re weapon i.e. components primer, case, bullet and the velocity are equal, and preferably done at the same time on the same day."
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Old October 14, 2012, 12:22 AM   #4
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Speaking just for your .45-70, my caliber of choice, don't worry about it unless you are so young and steady that you can win teddy bears at the boardwalk by shooting out the red dot. IMO, consistently reliable ignition by using powder that fills the case properly is going to serve you better than concern about the temperature. But it is a useful question.
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Old October 14, 2012, 07:50 AM   #5
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Location: Independence Missouri
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Yeah, I don''t take enough stock in that situation to let it bother my hunting, I also do load developement during hotter periods and it never seems to cause any problems for me. Don't worry about it.
Thanks for coming!
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