Help me understand zero and altitude

[NoDakfarmin]

I have a Mountain goat hunting coming up and have been shooting a lot in anticipation. I’m zeroed for 250yd at 1000ft altitude. The more I think about it, when I get to 5000ft wont by sero be off by a couple inches? Does everybody re zero when they get to hunting elevation or do I zero a couple inches low at home so it is accurate at 5000?

 

[thinhorn_AK]

I re zero when there’s a big jump in altitude. I’ve noticed a few inches so it’s worth doing but do your research because you may or may not be able to test your rifle at 5000 feet.

I basically live at sea level but went on some trips where the elevation was roughly 5000 feet, I got to a shooting range that was at 5009 feet and I was 2” high at 100. I gave it a few clicks and it was back to being dead on. Worked great on the hunt.

 

[wind gypsy]

Zero at 100 so altitude doesn't matter and you'll have a better zero with less conditions induced error.

 

[Macintosh]

Zeroing at 100 is more reliable with elevation changes, you wont see your zero change due to elevation at that range. It's the rest of your dope at longer range that will change. Plug it in for your parameters, but depending on what you need and your conditions it may not matter enough to actually matter.
For what it's worth, I live at a DA of 1300' (today), and I compared it to a DA of 5000' using my dope for my .270win. My solution only changed enough to register a .1 change beginning at 375 yards, and it's still only a click different out past 500. My short-barreled 6.5cm changed .1mil beginning at 350, but it was within .1mil out to 500 as well due to rounding to the nearest .1mil. So the effect isnt so significant depending on the maximum range you are counting on being able to shoot. In other words, going from roughly 1000' to 5000', on both of my rifles, if I was zeroed at 250 yards my scope doesnt have enough resolution to adjust the difference. It's near the end of my effective range I'd be more worried about (.1mil @ 400 or 500 on top of my wobble, ranging error, odd angles, etc probably starts to matter). Again, do it with your rifle and plug in numbers you think are accurate for environmentals, you may have a different setup, but at least on mine withthe conditions I used it might not matter. Now, if you were going to 10,000' and planned to shoot out to longer range, different story. My 6.5 dope below for comparison.

 

[JFK]

OP if your plan was to zero at 250 yards then hold a little high or low based on distance, the zero change from elevation won’t make a meaningful difference as it’s fractions of an inch. Your holds would be the main source of error. If you dial, then zero at 100, and shoot to your max distance at the higher elevation to confirm your solutions. Either way, I’d shoot once you reach your destination. If you find a problem you can deal with it. If you don’t it’s good practice before a hunt.

 

[nm.otter]

4DOF with Gun Angle makes this easy. Input local conditions when you establish your (hopefully 20+ shot) zero and then make adjustments for local conditions when you hunt/shoot.

 

[mxgsfmdpx]

OP. Listen to @wind gypsy advice on this one.

No need to dick around with zero angle, 200 yards zeros, and all the other garbage over complicating a good 100 yard zero. I used to be like this, it’s not the way.

Zero at your home range at 100 yards. Get a good and known solid zero. Go hunt anywhere in the world at any elevation and simply adjust dope for current feels like air (density altitude).

There is no need to adjust a zero once at hunting location unless the travel to caused an impact shift in the gun/scope setup. This happens more often than folks think and they blame “elevation” or other factors that don’t matter.