Temperature effects on zeroing

[CBDR]

First time post in this forum: My professional level of training to date is somewhere between zero an a mouth breather. I'm probably setting my self up for a good thrashing but here goes. So my build is complete and its off to the range I go. I'm 32 feet above sea level in Waycross GA (the swamp) Weather forecast calls for temps around 30 degrees, humidity levels will be somewhere around 50%. This is a night time hunting application. My zero will be 100m. Anticipated max shooting distance 400m. My question: if I zero at theses conditions will I see a difference during the same (or higher) humidity levels (100%) during the summer months where my temps can be around 90 degrees?
I'm a firm believer that the learning process never stops.
Cal 308 win
18" MTU barrel
Factory Hornady 178 ELD-X

 

[_Windrider_]

Will you see a zero shift at 100yds? Not likely, maybe a tiny tiny bit. But your drops will be different due to velocity changes. You using a ballistic solver, if so which one?

 

[CBDR]

I do not use a ballistic solver, just collect dope.

 

[Diver160651]

You will not see anything from an external ballistics due to drag of the colder air, only because your internal ballistics may produce a tiny bit less velocity than anmo baking in the sun.

That said, if your on the edge of a node (very unlikely with a 3o8 and your barrel) maybe somthing..

But the main culprit will be the shooter, extra clothes etc..

 

[CBDR]

Thank you

 

[_Windrider_]

Holy shit. That’s quite a setup for a mouth breather.

 

[Diver160651]

Thank you

There is your issue! It even colder at night!

 

[Snuby642]

I think 308 at 100-400 with 178 eld would be a very forgiving round.
Check it when it gets hot probably gtg.
My sons 308 is down for scope mount issues at the begining of load development.
Thought we would go nuts with loads just to find out a bad mount jacking with us.

 

[FishDr]

That’s quite a setup for a mouth breather.

This is very bad news … looks like I’ve not even arrived at mouth breather stage!!! Yep, it’s a journey.

 

[308pirate]

I do not use a ballistic solver

Why don't you?

There are free ones for your phone and there are free ones (which work exceedingly well) on the internet.

Using ballistics software isn't mutually exclusive with collecting dope. I use both. But using a solver accelerates the learning curve in a way that limiting yourself to collecting dope can never match.

 

[Deleted member 113831]

You will not see enough difference in your zero to matter. Humidity is a non factor for you ballistically. Drops will change slightly due to temp differences affecting powder burn rate, but at 400 yards I doubt you would even notice that very much.

Being in the humidty and heat of Georgia will show you some rather dramatic mirage effects that will play tricks on you though.

 

[Diver160651]

Maybe I missed something- I though the op was asking about his zero.

But if he is asking for his downrange dope sure he'll get a tiny at 400. but as Skookum mentioned it is more academic unless your going very slow with you heavy 308 in that short barrel - at 2400 you'll get .1mil if you average, but it is actually a bit less.

As know examples:
My load goes from a 1.43 @ 30° to a 1.39 @ 90° - so either way , I dial 1.4 @ 400

This weekends match was 45° at the start finished around 55°. This weekend I just stayed in the 70° column and it still facilitated the top spot. I've use the same dope card in the summer at 100° as I do in the winter, like Sunday and colder, with many top spot results.. The dope is really solid.

Below is an example of my stage cards that I pre-print in the match booklet is sent out before the match and the card I use if not. The interesting thing is once you only worry about the smallest scope adjustments you can make you'll note that the rounds are relatively temp stable out to 1K. Now this isn't so true at the Alaska type lows or and sandbox highs. You might find it interesting to look at my 70° and the the 50° & 90° columns.

All that said, if I know the match is in, let say Wyoming, I'll set the inHg for the expected location as well shift the expected main temp column, but I will still create the 40° brackets.

edited to add: Man this was hard to post with Siri - the examples below have include -AJ at full value 90° wind that round up my numbers a bit

pre-printed stage example

Normal dope sheet - used for UKD match etc

Blank stage when I do not have a mach booklet, but have time to write stage dope

 

[CBDR]

Maybe I missed something- I though the op was asking about his zero.

But if he is asking for his downrange dope sure he'll get a tiny at 400. but as Skookum mentioned it is more academic unless your going very slow with you heavy 308 in that short barrel - at 2400 you'll get .1mil if you average, but it is actually a bit less.

As know examples:
My load goes from a 1.43 @ 30° to a 1.39 @ 90° - so either way , I dial 1.4 @ 400

This weekends match was 45° at the start finished around 55°. This weekend I just stayed in the 70° column and it still facilitated the top spot. I've use the same dope card in the summer at 100° as I do in the winter, like Sunday and colder, with many top spot results.. The dope is really solid.

Below is an example of my stage cards that I pre-print in the match booklet is sent out before the match and the card I use if not. The interesting thing is once you only worry about the smallest scope adjustments you can make you'll note that the rounds are relatively temp stable out to 1K. Now this isn't so true at the Alaska type lows or and box highs. You might find it interesting to look at my 70° and the the 50° & 90° columns.

All that said, if I know the match is in Wyoming I'll set the inHg for the expected location as well shift the expected main temp column, but I will still create the 40° brackets.

edited to add: Man this was hard to post with Siri - the examples below have about include -AJ at full value wind that round up my numbers a bit

pre-printed stage example
View attachment 7010922

Normal dope sheet - used for UKD match etc
View attachment 7010930

Blank stage when I do not have a mach booklet, but have time to write stage dope
View attachment 7010931

Thank you Sir