Deviation due to heat/cold and humidity?

[dms416]

Assuming nearly all other factors being equal (rifle, shooter, optic, range,venue, ammo, etc.), what is the maximum amount of deviation one would expect to see from changes in temperature, humidity, and barometric pressure. Let's say we're talking 100 yards using the standard formula (.308 in 168gr out of a 24" barrel). Let's assume a cold bore was was taken every day for a year.

NOTE: the temperature here could vary from -5 to 95 (F) and humidity ranging from roughly 50-90%

Thoughts?

 

[ShtrRdy]

If you really want to know the details, you'll have to consult a ballistic program like JBM Ballistics. If you're interested in generalities, humidity doesn't have too much of an effect - more humidity causes less air density. Temperature can affect trajectory in a couple ways. One is the muzzle velocity of the bullet can vary with temperature, and the air density changes with temperature. As it gets colder, the air gets more dense and therefore the bullet will drop more over a given distance. Air Pressure has an affect as well. As the Air Pressure goes down, the air density goes down. (Air pressure goes down with an increase in altitude)

That being said, you won't notice too much difference at 100 yards.

 

[Graham]

Run the numbers on your ballistics program. Then you'll know.

 

[dms416]

+/- 0.1 MOA is what I'm getting when running 0 and 100 degrees with a zero at 50 degrees. So maximum deviation would only be 0.2 MOA?... I must have missed inputting any humidity, but does this sound right?