Zeroing rifle in high humidity

[TexanHunter]

If I zero my rifle here in south Texas and go hunt mule deer in Colorado will the humidity down here affect my zero in Colorado?

 

[Fireflyfishing]

The elevation change certainly will.

 

[farmermail]

A bit, yes. Elevation (atmospheric pressure) will have a greater impact.

 

[svivian]

For a 100 yard zero no

 

[StopMakingSense]

For any environment you’ll encounter hunting wise in North America (Texas to Colorado 14k) can you outshoot extreme environmental change within the 100 yard zero to notice a greater then say a .25” shift?

 

[MattB]

Humidity at 100 yards? I am going to go with “no”.

 

[SDHNTR]

Do you know what you are specifically asking? Will it change the zero, no, not measurably. But the ballistics from elevation, temp and to a lesser degree, humidity, absolutely will affect the flight of your bullet.

 

[fwafwow]

Do you know what you are specifically asking? Will it change the zero, no, not measurably. But the ballistics from elevation, temp and to a lesser degree, humidity, absolutely will affect the flight of your bullet.

Does it matter the distances shot?

 

[nobody]

Theoretically, yes, a 100 yard zero could change. But the change will be less than a click value of your scope, so it’s all moot since it’s not something you will be able to adjust out. You’re more likely to lose zero from a subpar system shifting in transit or something else loosening. As mentioned above, your ballistics at distance will definitely change, but assuming your rifle and scope are actually zeroed (not “about an inch high at 100” zeroed), and your rifle/rail/ring/scope combo is solid, your zero point won’t be any different in Colorado than back home.

 

[def90]

Find an online ballistics calculator and enter your bullet weight, barrel length, altitude, temperature and humidity in Texas and record what it says. Then enter the altitude, temperature and humidity that you expect to see in Colorado and and record what it says. It’s going to be different but probably not enough to make a difference to the average shooter.

 

[Koda_]

Does it matter the distances shot?

yes, a large change in elevation, past 300yds it can start measuring in inches.

 

[northernalpine]

The elevation change certainly will.

This.

Air density at higher elevation is going to be significantly less, making your bullet fly more efficiently, changing your trajectory/bullet drop. Your 100 yard zero won’t change but your Texas-based dope will shoot high at further distances because the bullet isn’t fighting through as much resistance.

 

[.270]

Yes it will but its more about the altitude then humidity as said above. I didn't have a problem when I live in Corpus Christi and traveled up to Colorado but I didn't take shots farther then 300 yards. The easy fix is just to adjust zero at camp before the hunt if you are worried about it.

 

[HighUintas]

Here's a 308 175smk zeroed at 100yd, 200ft elevation at 70F, 29.90"hg, and 50% rh.

First drop chart is for Texas, density altitude 1000ft at 70F (actual elevation 200). No change in zero, of course.




This one is for 8000ft density altitude, 50F. Relative humidity is negligible.




Change in drop at distance, no change at 100.

 

[RockAndSage]

An interesting question, but it really doesn't matter...because in travelling 1/3 the way across the country, you were of course going to check the zero locally anyhow, right?

 

[Fireflyfishing]

An interesting question, but it really doesn't matter...because in travelling 1/3 the way across the country, you were of course going to check the zero locally anyhow, right?

This is the correct thought process no matter how you look at ballistics tables.

Rezero and calibrate all your ballistics to the area you’ll be hunting.

 

[Fireflyfishing]

Look at what happens to the drop at 100 when I change the zero to 25 yards for the two locations. Also, notice how Berger doesn’t even list humidity as an input on their calculator.


In other words, there is a difference.

 

[northernalpine]

An interesting question, but it really doesn't matter...because in travelling 1/3 the way across the country, you were of course going to check the zero locally anyhow, right?

A rifle’s 100 yard zero doesn’t shift because you change environment.

This is the correct thought process no matter how you look at ballistics tables.

Negative, Ghost Rider. Unless you just enjoy shooting in new places, you should be confirming/truing your new drop chart on location, at a distance relative to your maximum effective range.

In other words, there is a difference.

Nailed it.

 

[fwafwow]

yes, a large change in elevation, past 300yds it can start measuring in inches.

Thanks. I had tweaked some inputs on a ballistics calculator for estimated changes in environmentals and thought the changes to come-ups were negligible until around 600 yards. I will go back to double check.

Edit - I confirmed for where I'm headed, the temps and elevation I'm expecting, and for the rifle/round in question, I'm expecting 0.1 mils of change until about 600 yards (so about 2" at 550 yards and 4.3" at 600 yards) if my math is right.

 

[RockAndSage]

A rifle’s 100 yard zero doesn’t shift because you change environment.

Negative, Ghost Rider. Unless you just enjoy shooting in new places, you should be confirming/truing your new drop chart on location, at a distance relative to your maximum effective range.

Nailed it.

Perhaps you missed my point: basic competency as a travelling hunter means you check your zero once you get local to ensure there have been no zero shifts during transit and to deal with any the rifle may have experienced.

The conversation above matters only as a part of theory or intellectual interest if the OP is exercising basic competence as a travelling hunter, in checking his zero once he arrives.