Does elevation change POI?

[Whitty]

Hey folks,

Heading to Wyoming to hunt mule deer late October and will be hunting around 7000 feet. Taking my Tikka T3 chambered in .270WSM and shooting 130 grain ballistic tips. Have zeroed in at 200yrds but live in SC around 900 feet elevation. Will the change in elevation alter my point of impact enough to worry about?

 

[Wworker]

The quick answer is yes, altitude/temperature/humidity will effect your point of impact (a few inches at 500 yrds). You can find ballistic calculators online to plug your info in to see how much at different distances.

 

[davsco]

i'm certainly hoping and planning on checking / adjusting my zero when i get out to colo.

tomorrow i'm actually hitting the range and seeing where i hit at 1, 2, 3, 4 & 500 and comparing that to my ballistics calculator ('shooter' app on my phone). hopefully it lines up perfectly, but if not, i'll take the spreads into account when i rerun ballistics way up in the colo hills.

 

[Gunnersdad49]

Yes. The real thing you are looking for is density altitude.

This is a quick comparison of a 6.5 at 900' and 9000' density altitude.

At 900', I need 28.75 MOA elevation and 6.5 MOA windage for a thousand yard shot and a 10mph crosswind.
Same situation at 9000' density altitude, 25.5 MOA elevation, 4.75 MOA windage.

So basically, thinner air means that the bullet will hit higher and be less affected by the wind.

 

[roadrunner]

Question has been answered. Might want to consider changing your zero to 300 though considering you're hunting mulies in WY.

 

[huntsman22]

Why?....

 

[tntrker]

I live in SC and shoot MOA at 400 yrds with my 30-06. Yes is the answer, but for my 180gr, it's only 1/4 inch difference (high) at 300 yrds sea level compared to 5,000 ft. I would and am going to be making sure that's correct when I get out there next month.

 

[KHNC]

Why?....

Yes, Why? I keep my zero at 100 for everything. But i have turrets for that purpose.

 

[chindits]

Me thinks roadrunner was suggesting a longer zero range so you don’t have to make any adjustments out to a certain range for a certain element of accoracy. For example, a certain 270 load with a 250m zero at 10000 feet will be 9 cm high at 150 m and 10 cm low at 300 m. For some that might be an acceptable measure of accuracy for aiming dead on from 50m to 300m. I didn’t check the numbers on his 300 yard recommendation but 250 m is close to 275 yards. Just a possible interpretation of another persons suggestion, usually a poor practice.

 

[Teaman1]

I think he's just wondering if there will be a difference in his 200 yard zero at home vs the 200 yard zero at 7000'

 

[duckhunter175]

Just came back from Wyoming- I live in TX- There are a lot of variables at play and for me my TX data came out within 1/4 moa out to 700 yards on my ballistic calc for Wyo data.

If you are in SC at 900ft and go to Wyo at 7000ft the air is obviously much less dense. BUT- your temps are going to be much colder in WY than in SC when you zero'd and it was say 80+ degrees outside. For my load and rifle it ended up nearly the same. I suggest getting a ballistic app and run the numbers then it is easy to verify on arrival.

For me- my confirmed data in Texas was a 250 yard zero that was 1.7" high at 100 yards and 2.4" low at 300 but at 1400ft and 88 degrees. Then I ran the calculator for wyoming (50 degrees and 7000ft) and got almost the identical data. When I arrived to Wyo my actual shots matched the ballistic app.

 

[Jardo]

Just sight in for 200 yard zero when you get to Wyoming. Never travel on airplanes with your gun and not check your zero anyway.

If your dialing, you probably already have a ballistic calculator. If not dialing, a 200 yard zero is good to 300 yards with a .270.


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