Point of Impact at High Elevations

[Tsimms]

Headed to Colorado Sept 19th for a rifle hunt (RFW Gun Tag) and was curious as to how much difference the elevation makes in point of impact if sighted in at 800' above sea level? We will be hunting anywhere from 8,000 to 10,000' (Hopefully, if the fires don't burn the ranch down). I have been practicing a lot at ranges out to 500 yards with my 280 AI. Any experienced advice someone could give me would be helpful. Do I need to zero my gun once on the ranch? Thanks for any insight.

 

[String&stick]

I would definitely check zero when you arrive. This would confirm or put to rest your fear with elevation and ensure nothing happened in route to your scope?

 

[Laramie]

The Hornady ballistics calculator will give you some data if you know your bullet speed/weight etc. I do recommend shooting once you are out there to check. Other factors like temperature, humidity, etc can have minor impacts as well. My rifle zero is changes almost 50 yards when I hit the high country. I sight in at 200 at 1500' elevation. At 9000', the new zero is 243 yards. I use a long range reticle with multiple crosshairs. If you don't use something similar, I suggest sighting in with the MPBR system and use 8" for you acceptable kill zone.

 

[Brendan]

Your zero won't be off much, but point of impact at longer range could change a little bit. For me, (300 WM) my POI will change by 4" at 500 yards from sea level to 12,000'

Best to print your range card, dial chart, whatever for the altitude you'll be hunting at.

Example calculator here:

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[erle1139]

within 300 yards you won't notice much difference. Out to 500 yards you could have 4-5" +/= less drop. I come from sea level with my 308, and limit my shots to within 400 yds, so the altitude doesn't really mess with POI. where you'll notice the most difference is at the ranges where you start to see significant bullet drop, which for my 308 is 500+ yards. not sure about a 280, but you can run it through a ballistic calculator if you know MV.

 

[Tsimms]

Great information. Thanks guys. I have my rifle and ballistics information and a ballistics chart for 800' elevation and also 8,000' printed. 3,269 FPS with a 139 Gr bullet.

 

[TxxAgg]

Tagged

 

[wytx]

Check your rifle when you get there, always.

 

[Wapiti1]

Great information. Thanks guys. I have my rifle and ballistics information and a ballistics chart for 800' elevation and also 8,000' printed. 3,269 FPS with a 139 Gr bullet.

That is really all you need. Check your zero when you get there, and off you go. There isn't anything special you need to do other than using the correct trajectory info for the elevation you are at.

Jeremy

 

[ChrisAU]

This is the best argument for a 100 yard zero vs a 200 yard zero. Zero at 100 yards at virtually any elevation/temp and you likely won't have to adjust zero when traveling, you'll just use different dope charts based on the new location/environmentals.

 

[CavemantheHunter]

At 500 yards, my 338 POI changes about 6" going from 1000 El to 8000 El, but the POI changes exponentially once you go beyond 500 yards.

 

[dmc]

I always try to confirm zero after travel.

Another thing that could be of interest would be a ballistic app on your phone - I use Shooter and like it. Set up your rifle, load, zeroing conditions. Then when you get to elevation you can download all the air density info from the nearest weather station. Automatically gives you a new chart. I then screenshot it and make it the locked page photo on my iphone. Has worked well in the past for me.

 

[rclouse79]

I am new to scopes with turrets and ballistics calculators. I was playing around with the Hornady app and was surprised to see the number of clicks didn't really change when I entered huge swings in temperature or elevation for the ranges I would hunt (inside 500 yards). I think it is more important for guys shooting longer distances, unless I am using the app incorrectly.

 

[DropTyne]

This is the best argument for a 100 yard zero vs a 200 yard zero. Zero at 100 yards at virtually any elevation/temp and you likely won't have to adjust zero when traveling, you'll just use different dope charts based on the new location/environmentals.

I would argue to know your dope chart for the elevation ahead of time and sight your rifle for a POI with the 200 yard zero at 100 yards at home. When you get to your hunt location, check your zero and rock on. This is the same logic as you state with the 100 yard zero.

 

[sneaky]

Great information. Thanks guys. I have my rifle and ballistics information and a ballistics chart for 800' elevation and also 8,000' printed. 3,269 FPS with a 139 Gr bullet.

What length barrel you getting that speed out of a 280AI? I'm not pushing my 140gr loads nearly that hard or hot. My accuracy node was much lower than that.

Sent from my SM-G955U using Tapatalk

 

[Tsimms]

26” number 4 Hart barrel. 62.5 gr reloader 22. It’s smoking. Keith Carrigan (KC’s Customs) built my gun about 25 years ago. He was one of the best with a 280 AI. Sadly he passed away about 7 years ago. I’ve been smoking an 8” steel plate at 500 yds for the past 3 weeks twice a week. I feel really good about my accuracy just wasn’t sure about how the elevation change would affect things. I have the Hornady app downloaded and it has been spot on around here. I have a dope chart for 8,000’ made up and found a public range in Kremmling CO that we will shoot at the day before our hunt starts. I appreciate everyone’s help in this thread. I’ve followed this forum for a few years but never posted. Nice to get this help without the drama. Thanks guys.

 

[Brendan]

100 Yard zero fan here. No need to change zero to account for the elevation difference as it'll be so small, and I don't feel like a 200 yard zero buys me anything. Even though for my setup it'd be a one click difference at 200 yards, I don't want to be pulling turrets and re-setting zero stop if I don't need to.

 

[Lwilliams]

Print several cards for density altitude in 1000’ increments and invest in a Kestrel. Or invest in a Kestrel with a ballistics built in and run that.