Question for the really good shooters here..

[Critch]

Does temperature have any real effect on how a bullet flies? Let's say you have a Model 700, shooting the same bullets but at different temperatures, is there any appriciable difference, especaily in a sniping situation?

[snakehunter]

Yes. The rule of thumb I follow is add/subtract 100 f/s for every 10 degrees F change in temperture of the propellant.

[Gunner]

Yes it has. Out of my .308Win the POI is at 300m at -7°C aprr.11 cm lower than at 20°C. Snakehunters formular seems to fit. Or an other thing is to put the rounds in your jacket when you leave home, than the POI is even the same when you load the round immediately before you shoot in your rifle.

Regards

Gunner

[hagar in SC]

I'm not a really good shooter, but I do know the answer to that. Yes, cold weather will affect your zero. Probably not much at 100 yards, but at 200 it may be 4 inches lower than your summer zero.

I shot my scoped rifle in a 1000 yard match, when we started temps were in the low 50's. After I went to the pitts, and came back to the firing line and shot my next series, temps were up in the low 70's and I had to come down at least 30 inches (3 minutes).

There are a lot of ballistic programs available that will show you exactly how your bullets will behave in different temperatures, humidity and altitude.

[Jim K.]

It is not just the propellant temperature. Atmospherics can affect the bullet. For example, high humidity can slow a bullet, while thin air at high altitudes can allow it to fly faster and farther. These changes are usually small (no, the humid air didn't cause you to miss that buck by six feet!) but we can be aware that wind is not the only way air can affect accuracy.

Jim

[Gunner]

Jim,

there are various points that will have an influence on the bullet and some of the shooters do not give them enough attention. Humidity and air pressure (and much more influence combined with warm air) are fixed sizes you have to deal with. Good point! I learned to write each shot under each circumstance to get a knowledge library for my ammo, rifle and scope. One of the best advices on shooting.

Regards

Gunner

[Bill]

Older powders are affected by varying temperature much more than the newer Hodgson powders.

I have not experimented at ranges long enough to see the effect, but the velocity drop can be seen via the chronograph. The difference when using the newer powders is noticably less. Trajectory should be less affected as well.

[John Kepler]

It is not just the propellant temperature. Atmospherics can affect the bullet. For example, high humidity can slow a bullet, while thin air at high altitudes can allow it to fly faster and farther.
Jim

Not picking on you....but you're not a Long Range shooter, are you?

Jim is repeating a myth that seems intuitively to be valid...."high humidity can slow a bullet". Unfortunately, as in a lot of Long Range shooting, what intuitively seems like it should be correct is completely and counter-intuitively incorrect as anyone that actually shoots at longer ranges (800-1000 yds) has seen "up close and persoanl"! In spite of our perceptions of "heavy/muggy air"...water (H20) is quite a bit lighter than the bulk of our atmosphere, nitrogen (N2)! You do have to make a correction for high humidity/lower air density....but its due to the bullet retaining velocity, not losing it!

Also, a "typical sniper shot", like a "typical hunting shot", is of the 200-300 yd "chip-shot" variety...not something like 1000 yds (the art of being a sniper isn't being a "steely-eyed hard-holder", it's in being a ghost and putting himself in position for that "chip-shot" anyone can make!