AR zero weather effect?

[powderedtoastman]

So, I zeroed my coyote AR at 100 yards this past October. I believe it was around 75 degrees that day, and dry. Tomorrow morning I'm going out to Nevada after yotes, and it is forecast-ed to be about 17 degrees at 6AM, and 45 degrees around 2pm.
At 100 yards, how much is my zero going to be affected? Is it worth it to find a spot and establish 100 yards tomorrow morning and re-zero?

I'm shooting a stainless 20" 1x8 twist .920 5.56 barrel, running 77 grain Berger OTM/BTHP's with 22.5 grains of Hodgdon 4895 behind it, if that makes a difference. My average velocity over 10 shots when I zeroed it was 2570FPS.

[bigbearbear]

I shoot my AR at Los Altos 100 yards rifle range and have been doing so on and off since last summer. I've noticed that the temperature does not affect the zero, but wind certainly will.

There was one day where it was really windy and the bullet drifted by a few inches. It was pretty amazing how much a 55gr .223rem round drifts in windy days. So when you're out in the wild, watch for windy days.

[SuperSet]

I just did a quick comparison in Strelok with that ammo for both 20F and 60F and the difference was about .5" at 200y and 1" at 400yd.

[powderedtoastman]

I just did a quick comparison in Strelok with that ammo for both 20F and 60F and the difference was about .5" at 200y and 1" at 400yd.

I JUST now figured out how to do the comparison in the "shooter" app on iphone, and had the same difference.

Bear: I messed with my 55gr spire points at 300yds, and a 15mph wind seemed to throw them off by maybe 2-3 feet, while my 77's were still hitting a 12" plate, although at the edge of it. I'm still fascinated by ballistics!

[highpower790]

I think the only thing that will make any difference will be a big change in elevation.
My zero around SF bay will change -1/2min if I shoot a match in Salt Lake City.

[powderedtoastman]

I think the only thing that will make any difference will be a big change in elevation.
My zero around SF bay will change -1/2min if I shoot a match in Salt Lake City.

Ok, so my elevation will definitely change. I zeroed at Sac Valley at +/-75 degrees, and I'll be around 4200' elevation and +/- 20 degrees tomorrow. I think I'll find a spot to re-zero before my hunt.

[highpower790]

Ok, so my elevation will definitely change. I zeroed at Sac Valley at +/-75 degrees, and I'll be around 4200' elevation and +/- 20 degrees tomorrow. I think I'll find a spot to re-zero before my hunt.

What is the barrel length that your rifle has.I get 2800fps with a 75gr,if your barrel is longer than 20",there may not be much of a difference.

[powderedtoastman]

I'm shooting a stainless 20" 1x8 twist .920 5.56 barrel, running 77 grain Berger OTM/BTHP's with 22.5 grains of Hodgdon 4895 behind it, if that makes a difference. My average velocity over 10 shots when I zeroed it was 2570FPS.

[highpower790]

The 20"service rifle I shoot with a 1/7.7twist gets 2800fps,at your velocity a zero change of 1min is possible.

[powderedtoastman]

The 20"service rifle I shoot with a 1/7.7twist gets 2800fps,at your velocity a zero change of 1min is possible.

Much obliged, I think I'll re-zero and/or at least verify my zero before I get at them tomorrow!