Altitude changes with load

[Tac-O]

It looks like I will be rifle hunting this year, somewhat unexpectedly, and for the first time! I've only ever hunted archery and with a slug gun.

. I haven't got out to practice in the field yet, mainly because I've just been learning about my reloading and figured I likely wouldn't rifle hunt at a much higher elevation and potentially longer distance. That being said, I haven't shot my hunting load at high altitude. Because I haven't practiced in the field yet, I need to do so to determine what my max responsible shooting distance will be. I can say that it is definitely not farther than 500 and very likely not farther than 300. We'll see how it goes. Maybe even just 200.

Anyway, in preparing for hunting with my hunting load, even if I won't shoot farther than 200, I'd like to know what I should look at with my load in the case that I have a 400 yard shot at 10000 feet at near freezing temperatures.

I've been shooting at about 5000 feet
My load has been developed at about 90 degrees F, low humidity and highish atmospheric pressure.

.30-06
Speer 180gr hot cor
H4350
Cci200

I haven't chrono'd this load yet. From what I can find on h4350 temp stability, it looks like there might be a 20fps speed difference going from 90F to 30F, so that is only about 3 inches at 500 yards. So the temperature wouldn't affect my speed enough to worry, especially if I'm limited to 200-300 yards.

What about atmospheric pressure and humidity? Would they change the speed more significantly than temperature? Could these two drastically change this load's group size?

Next steps: measure velocity, shoot at 200, practice in the field.

Thoughts?

 

[Mikecr]

Nothing about alititude will change your muzzle velocity. You should just enter the numbers into your ballistic program to see what changes in adjustments per distance will be. Your zero will shift a tiny bit as well. Best to shoot your zero at altitude.

 

[Tac-O]

Nothing about alititude will change your muzzle velocity. You should just enter the numbers into your ballistic program to see what changes in adjustments per distance will be. Your zero will shift a tiny bit as well. Best to shoot your zero at altitude.

Fantastic. Thank you!!

I'll have to look around and see if I can find a place to shoot at 9k or 10k feet without screwing up someone's hunting.

 

[243winxb]

 

[Tac-O]

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Too bad I can't hunt at 15k.... It would turn my '06 into super magnum ballistics

 

[Stammster]

What kind of critter are you hunting at 10,000 ft?

 

[243winxb]

What about atmospheric pressure and humidity? Would they change the speed more significantly than temperature? Could these two drastically change this load's group size?

 

[Tac-O]

What kind of critter are you hunting at 10,000 ft?

Elk. I'm in Utah and primarily hunt the Uintas, which can have elk at 11000 in some areas.

 

[Tac-O]

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That makes surprisingly little difference!

I have the strelok app, but haven't played with enough to figure out a couple of the input options. I'll dig into that a little more

 

[BrentM]

As others have said internal ballistics are not changed much unless your powder is temp sensitive and on the ragged edge of hot charge. External ballistics is what you will be concerned with.

Being a bow hunter, like myself, I'd personally not be attempting anything over 300 since you haven't practiced, don't know your ammo and weapon, and don't have a fundamental understanding of ballistics yet. Just get closer, within 300, and zero your rifle for 200. Shoot paper at 300 and record the drop. Use this info to help hold high on a 300 yard shot or hold dead center on 250 and less.

I understand that long range is the rage and everyone wants to be involved but mountain shooting throws wind, up and down drafts, and angle shots into the mix with less than ideal shooting positions. Throw a 10 mph wind, 20 percent slope, and a crappy shooting position and a 500 yard shot becomes a miserable experience. I've guided a lot of hunts that would've gone wrong if I myself didn't spend a ton of time shooting all year in terrain. I don't consider range time practice.

 

[jrock]

I tested this once. I use absolute pressure from my Kestrel. I zeroed and shot a drop test out to 800 yards at about 700 ft above sea level. Then took it up to 7,000 ft and shot at 1,100 yards using the adjusted absolute pressure in the Shooter app. First shot hit! I strongly recommend validating any program if you can. I don't remember any of the adjustments or difference in POI, just that it worked and my equipment was validated.

 

[Tac-O]

As others have said internal ballistics are not changed much unless your powder is temp sensitive and on the ragged edge of hot charge. External ballistics is what you will be concerned with.

Being a bow hunter, like myself, I'd personally not be attempting anything over 300 since you haven't practiced, don't know your ammo and weapon, and don't have a fundamental understanding of ballistics yet. Just get closer, within 300, and zero your rifle for 200. Shoot paper at 300 and record the drop. Use this info to help hold high on a 300 yard shot or hold dead center on 250 and less.

I understand that long range is the rage and everyone wants to be involved but mountain shooting throws wind, up and down drafts, and angle shots into the mix with less than ideal shooting positions. Throw a 10 mph wind, 20 percent slope, and a crappy shooting position and a 500 yard shot becomes a miserable experience. I've guided a lot of hunts that would've gone wrong if I myself didn't spend a ton of time shooting all year in terrain. I don't consider range time practice.

Yes I completely agree. It is EXTREMELY unlikely I'd even consider a shot longer than 200-300 given my current skill level. My hunt is Oct 3. So I figured I'd see how my field practice goes over the next month and find my max safe distance for perfect conditions as well as light wind. For example, if it goes well and I get my drops and drift figured out up to 400, and then I have an ideal opportunity for 400 (flat ground, maybe prone position, 5mph wind max) then maybe I would consider taking the shot IF I can't get closer.

I don't really want to hunt long range. I consider 500 long range. I'm a bowhunter at heart, so I always want to get as close as possible! I just want to be able to shoot to 500, just as a tool to make sure I can fill my tag. But of course, that's along down the road somewhere after I get more experience.

I've dialed back my shooting expectations from 700 last year when I first got my rifle to 200-300 now. I've learned a lot since then haha

 

[skipglo]

Fantastic. Thank you!!

I'll have to look around and see if I can find a place to shoot at 9k or 10k feet without screwing up someone's hunting.

You could go to Everest! No hunters there...but you may play Hell with the climbers base camps!

 

[Pinoniper]

I applaud your self awareness and recognition that, this year, you are going to limit your shot distance because you know the limitations of your current level of rifle experience. With those stealth skills from your archery background, you should be able to get plenty close enough. Best of luck!