If I sight my scope at 3000ft for a 250yd zero and climb to 12,000ft what will be my new zero?

Then, if at 12,00ft I readjust for the original 250yd zero, what will my new drop at 550yds be, given that the 250yd zero at 3,000ft gave me a 47" drop?

Load is 7mm Hunting VLD at 2,780fps.

Thank you for your help.

Alvaro

It's not the altitude per se, it's the barometric pressure you need to factor in:

http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html


Use the table provided in the link and you can figure out your drops with any ballistics program.

If I sight my scope in a barometric pressure environment of 26.8 inches of mercury, and climb until I reach a place with a barometric pressure of 18.9 inches of mercury, what will be my new zero?

Then, if at 18.9 inches of mercury I readjust for the original 250yd zero, what will my new drop at 550yds be, given that the 250yd zero with 26.8 inches of mercury gave me a 47" drop?

Load is 7mm Hunting VLD at 2,780fps.

Thank you for your help.

Alvaro

The quicktarget that comes with Quickload can account for altitude, but I find that drop charts are not near as good as getting to the hunting area weeks early for scouting and target practice. I put glow tape on the turret and marked on it at the elevation and range I will hunt.

That was my personal long range breakthrough in 2013. No calculations, no drop charts, mark the turret based on reality.

A wise thing to do, clarkm, if I could, but this will be in the Tien Shan Mountains in Central Asia and I will just go there for the hunt.
There is no way I can go now, climb to 12,000ft and adjust the turret, return home, and go back to Kyrgystan back for the hunt next month.
Alvaro

Run the numbers. Typically the factors don't really mean a miss until you start getting past 600 yards. Beyond that you need to start having some sort of ability to measure barometric conditions. It Becomes a really big deal at 800 and beyond. Just guessing without looking I bet your 250 yard zero would not change much.

If you're contemplating a 500 yard shot, you really need to develop the capability to figure this out for yourself.

Or to put it another way, you shouldn't rely on someone else to figure it out for you. Especially on the internet.

Go to this link (Berger ballistics calculator) and input your numbers. You don't need barometric pressure, just altitude. Then check to see if this model holds true for your locale:

http://www.bergerbullets.com/ballistics/

Given a 250 yard zero:

Drop at 500 yards

At 26.8 inHg = 29"
At 18.8 inHg = 27"

Dogshooter,

A 250yd zero at 3,000ft -> 29" drop @ 500yds
A 250yd zero at 12,000ft -> 27" drop @ 500 yds...

OK

But what does the 250yd zero at 3,000ft transform into when you take your gun to 12,000ft??

That is the question...

Thank you!

Alvaro

12,000' IS 18.8 inHp

Barometric pressure and altitude in ASL (average) are the same thing.

At 3000' (26.6 inHg) 250 yard = +2.3" @ 100 yds
At 12000' (18.8 inHg) 250 yard zero = +2.2" @ 100 yds

So, if you make no changes, assuming your rifle stays zeroed on the 10000 miles worth of flights.... the difference is about 2-3" less drop at 18.8 inHg than at 26.6" inHg.... meaning not enough to matter.

Any difference will be in fractions of an inch.

Most any ballistics calculator will give you "specifics", although they are really still just educated estimates

Sometimes you just have to try for a long shot, and for this reason I practice and practice and practice, and I am shooting my 7x65R K95 kipplauf twice every week from field positions. This is Friday's attempt at 550yds, lying over my pack (1" grid):


I would have guessed I am developing my capabilities correctly and that there was nothing wrong seeking for technical advise here, as there are very knowledgeable posters willing to help...

I prefer to get close as for me the challenge a difficult approach offers is more interesting than an aseptic 700yd shot. But this is just my personal preference and I fully respect others' preferences.

As an example, this photo is from where we spotted my Blue Sheep. I was hunting in the Himalayas, in Nepal:


I could have put it down with a 700yd shot, I think, but I'd rather try getting closer and making it more "personal". So we were on the move


We went over a saddle at 16,400ft:


And, finally, almost too late into the day, and too far from my tent, I could take my shot at 250. With this result.



At 55, I can't cope very well with anybody telling me what I should or should not do, but let us leave it there.

Alvaro

Alvaro,

thank you for the great pictures of the mountains. Talk to you soon.

C.

Badass hunt! I can't think of a more perfect location for a "watch"! Great sheep and unique beautiful country. You're a lucky man.

Super cool hunt, can't wait to see pics of the next one. I hope I can climb like that when I'm 55....

Best of luck on the up coming hunt.... I'm pretty sure that kind of shooting will get it done. Nice to see someone taking their hunting marksmanship seariously from field positions.

Out of curiosity, have you hunted Barbary/Aoudad?

Yes, I seek technical advice here too. But I think asking someone else to calculate where your bullet will impact at 550 yards is going beyond "technical advice."

I wish you good luck on your hunt. If it were me, I would not trust someone else's answer on where my bullet would impact at long distance, unless I could independently verify it myself.

Because if you get a 550 yard shot, knowing where your bullet will impact is 100% your responsibility.

+1

smokepole,

I am not asking.. uuhh! where will my bullet impact at 550yds? like I was stupid... I shoot quite a bit, as I said, and I know quite well the real trajectory of my gun and load up to 550yds (500m) which is the distance I regularly shoot at for practice.

See another target from another day.. On this occasion it was 440yds (400m), as I check the adjustments in my ballistic turret every 100 meters, not trusting published bcs or any software's prediction. The red bull is 2" diameter.


But I also do quite a bit of hunting to practice my shooting, like my yearly trips either to Namibia or to RSA, or to both countries in the same year, to do culling. These photos are from this year's trip. I took my 6XC barrel loaded with 90gr Accubonds, 105gr Hunting VLDs and A-Maxes.

This big baboon fell to an A-Max at 563yds, when the poor bastard thought he was safe:


Here is the result of a morning sprinbok cull hunt. In the day I killed 26 with 27 bullets, from 330 to 566 yards:


So yeah, basically I can say that I know where should my bullet hit...

What I am asking is for an indication of what does the book say on how will altitude affect my trajectory...

I have hunted seven times above 11-12,000ft in the Pamir, Tien Shans and Himalayas, and when I have test shot the gun before starting the hunt I have always noted the bullet would print slightly high. Not as much as to touch the scope, but I always had the idea of dialing 1 to 3 or maybe four clicks less depending of the distance, should a long shot present itself...

In October you can find me in the Tien Shans, in November in the Alps, and in March in the Himalayas for my second hunt there.

Here you can see one of the Alpine Chamois from last year... http://www.youtube.com/watch?v=38ksXxy5cdk&feature=youtu.be Same gun, 6.5x57R barrel loade with 140gr A-Maxes.

Best regards,

Alvaro

Well, my apologies then. It sounded to me like that was what you were asking:

Maybe I did not express it properly, or maybe you do not want to understand it and not having anything else to do you are trying to have fun on me, or maybe you are just a [bleep], but I did not ask where will my bullets land at 500 meters.
I asked that given a well known point of impact at 500 meters what will the effect of a 9000ft climb will be.
Which is something different.
Do not bother to reply as I will put you on my ignore list and never read anything that comes from you.

BBerg, your original post shows you are not yet thinking in the terms of a long range shooter. You seem to have the skill and most of the equipment.

Why not make the few adjustments necessary to take your long range game to the next level?

No, I was not trying to "have fun on you." What I was trying to do (at first) was give you the tools you need to figure out the answers to your questions on your own rather than asking someone on the internet to figure it out for you.

And even with those tools laid out for you, you sat back and let someone else figure out what your new drops would be.

And yes, asking what your new drops will be at your high-altitude hunting location is the same as asking what your new point of impact will be. Posting pictures of dead animals can't change that.

I was under the mistaken assumption that someone who spends as much time and money on hunting as you do would naturally want to take personal responsibility for something so basic.

That's what it comes down to.

It seems like Berg is just a little better than me, so I am interested in everything he writes.

I am trying to break through the 500 yard hit anything barrier and [sure hit] hunt at 600 yards. I have been trying for 5 years.

As I read a lot of postings similar to this one I never cease to be amazed at the amount of people that have problems placing a shot where they wish at distances of 500 to 600 yards. Either they don't know the first thing about proper marksmanship procedure or they have 'boat anchor' material for rifles!! Here's a simple hunting rifle in .308 Winchester that is a 'hammer' at the above distances!

Hunting Rifle by Sharps45 2 7/8, on Flickr

Sorry R, but that rifle is obviously messed up, look where the bolt handle is!!

I love my .308 too. Accurate, and a pleasure to shoot.

Berg obviously doesn't know about Ballistic AE or own a "watch".

He can always post a thread and ask what time it is........

You guys are just crancky. Bunch of women. Go out and get some...

I'm not cranky. Up yours though.

'Watch' Out now..... got the time too....

Tidings of comfort and joy to you, too. Hope you have a very good season - where ever and whatever you may be hunting.

Thank you, and same to you. I'm eating some fresh elk shank stew right now, nothing better IMO.

Damn, that spot looks familiar. Fax me the altitude and coordinates so I can confirm I've been there. If you don't mind.

Altitude is on the watch.... Canada is 4 miles north....

I'll need longitude too.

Fresh elk is, IMHO, indeed very hard to beat. Good for you.

This year at Quemado, I was hitting the steel out to 300 yards, consistently without changing the zero, from Arkansas at 240 ft to where we were shooting at around 7500 ft. I did not think to check on paper, just shot. Using a 7mm-08 improved and 120 gr ballistic tips. Maybe Dennis will chime in with the actual distances. miles

Here's a pretty good online ballisitic calculator. You can manipulate elevation and zero distances amony many other things.


http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi


Aside from atmospheric pressure, Another factor going from 3000 feet, up to 12,000 feet in elevation may be your muzzle velocity. MV may be lowered a signinficant amount by the drop in powder temperature.

Using Reloder 22, and Reloder 17, I see approximately 1 fps loss in MV per degree Fahrenheit.