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Weather conditions on shooting?

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Replied by JustMe on topic Re:Weather conditions on shooting?

What mmsssh is describing is density altitude. As the temperature decreases or increases, the density altitude decreases or increases respectively. As the temperature decreases, the air's density gets greater (the air gets thicker) since the molecules in the air are packed closer together the colder the air gets. Consequently, the bullet has to push its way past more air molecules the colder the air gets which creates more bullet friction with the air and slows the bullet down. So for the same distance traveled over the ground (600 yards), the longer the bullet is in the air and the longer gravity has an effect on it pulling it down. As the temperature increases, the air gets thinner and there is less bullet friction with the air so the bullet travels faster and the bullet hits higher. The density altitude also changes as you climb in altitude. So, if you live on the coast at sea level and then take a hunting trip to Canada where the median altitude is 5000 feet or above, your bullet will hit higher since the altitude density is less in the mountains than at sea level therefore fewer molecules the bullet must push past in the air. Humidity also affects air density. The higher the humidity, the more water molecules are suspended in the air which makes the air more dense and the more molecules the bullet must push past. The air can hold more water molecules the warmer it is which is also a factor.

To summarize, four weather conditions affect the bullets flight path: wind, temperature, altitude, and humidity. And for real long shots the rotation of the earth while the bullet is in flight, the spin of the bullet which reacts with the air friction causing the bullet to change trajectory and some other factors which are technically not weather conditions.
Last edit: 13 years 5 months ago by JustMe.
13 years 5 months ago #5979

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Replied by Hot Lead Zapper on topic Re:Weather conditions on shooting?

What I
Last edit: 13 years 5 months ago by Hot Lead Zapper.
13 years 5 months ago #5983

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Replied by Edge on topic Re:Weather conditions on shooting?

In addition to the above comments, if you are a reloader, you need to watch what powder you are using.

My friends and I have done tests where in the middle of summer we'll put some reloaded rounds in the freezer at the range on a hot summer day. We'll spend an hour or two shooting and getting a good group or two. Then we'll go grab the rounds out of the freezer and shoot them. It's amazing to see that the POI will change and some will change a lot, depending on the powder used.

You need to shoot all year round, and see what your ammo will do in the different weather conditions. I have records for shooting spring, summer, fall, winter, rain, snow, and winds of all velocities.
13 years 5 months ago #5990

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Replied by JustMe on topic Re:Weather conditions on shooting?

You guys are right on!!! There are many many factors which change your POI as you guys have stated, weather affects bullet drop, efficiency of powder burn, primer ignition efficiency, barrel diameter size, density altitude, etc., etc. As Edge alluded to, rather than try to calculate all these factors, it easier just to resight your rifle in for each condition you find yourself in. If you predator hunt in the middle of the summer, resight for those conditions, if you find yourself in the cold mountains, resight again while in the mountains. This way you don't have to try to recalculate how to dope your scope for the changing conditions. What these discussions are good for is to make sure folks know that weather changes will change your POI, so be prepared to change your scope zero when weather conditions change. Don't be uninformed and think just because you zeroed your scope at home at sea level that you are going to be able to hit that whitetail in Montana. You need to resight that rifle when you arrive in Montana.

I ran into a situation while hunting in Colorado at 9000 feet above sea level. I had reloaded some 30-06 with Winchester basic "rifle" primers. They shot well at sea level and 40-90F. When we arrived in Colorado the temperature was 40F degrees and we resighted our rifles. The next morning the temperature had dropped to 10F and the next morning after that, the ambient temperature had fallen to -40F with a wind chill below that. Well, the rifle primers wouldn't ignite even though the firing pin made deep dents in the primers, so that elk got away after cycling 5 rounds through the chamber. I ended up pulling those primers and reloading with "large rifle magnum match" primers. Haven't had a problem since.

Of course, if you are trying to be covert and not let the enemy know you are in the area, you can't wander around shooting at rocks all the time to check your zero. Then doping is mandatory.
Last edit: 13 years 5 months ago by JustMe.
13 years 5 months ago #6000

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