Exteme temperature shooting

[Shifty]

So I zero my firearms at an outdoor range, usually on comfortable days temperature wise. I know a little about physics and gas laws and whatnot, and it got me thinking. Where I live, we hit 115 degrees in the summer and as low as 20 degrees Fahrenheit in the winter.

My question is, do any of you have any experience showing that a plus or minus 30 degrees gradient will change a point of impact to a noticeable degree? If so, at what range? Just curious. I know precision shooters obsess over this kinda stuff.

 

[rule303]

To a point, yes. Each load is different, some powders are more temperature sensitive than others. I have seen velocity deviations over 100fps with the same load in the same gun between 90 degrees and 0 degrees. Any colder than that, I can find something else to do besides chonographing loads at the range.

 

[gbran]

I have to admit I rarely shoot on very hot or extremely cold days. I'll guess this makes little difference over the range of temps I shoot.

 

[jmr40]

With rifles expect 1-2 fps change in velocity for each degree of temp change with most powders. Colder = Slower, Hotter = Faster. Handguns, probably less. A change of 100 degrees can make a difference, but most people practice and develop loads at around 50-70 degrees and rarely see more than 30-50 degrees difference. Usually not a problem.

There are some powders far less sensitive and you will see differences of only around .5 fps for each degree of temp change. Military specs call for such powder.

Shooting slower in cold temps is one thing. A load that is already near a max load could be too hot and over pressure if extremely hot. A gun left in a car in southern states can reach 140 or more on a hot sunny day.

 

[SilentStalker]

I can tell you that there is usually a .2-.5 mil difference in most of my bolt guns with temp swings of around 35-50 degrees of that helps anything. As already mentioned by someone else there are a lot of other variables that come into play here with temp but generally speaking if I am shooting the same rifle, bullet, powder, locale and all other things being equal other than temp then yes there is a swing of .2-.5 mils for me. I hope that helps. I have also noticed that some rounds are much more effected by this than others. Obviously, the flatter shooting the round the less impact this will have.

 

[mboylan]

There are also some fast pistol powders that are reverse temperature sensitive. They shoot slower at high temperatures and faster at cold temperatures.