Shooting at higher altitudes

[spleify]

I see every once in a while someone will make referance to altitude when shooting. Does it have an impact on how your firearm shoots, or on accuracy?

[trlcavscout]

The difference in pressures at different altitudes will change your POI up/down. As well as humidity and temp.

[KFinn]

Correct me if I'm wrong because I am still in the beginning stages of learning myself.

But specifically, higher altitude = less dense air = less drop and higher velocity at target than lower altitude?

Hotter air and less humidity = similar results as above since the air is easier to cut through

wind seems self explanatory.

[spleify]

Ingteresting, it makes perfectly good sense I just never thought of it.

So, if you site your gun in at 200 yards in the mountains at 10,000 ft, then go some where and you are at sea level your POI will essentially be lower, correct?

Thanks

[Irving]

I was going to ask about available oxygen to feed the explosion, but it seems like since the case is sealed, it wouldn't really be an issue. Maybe less flash though?

[Mtn.man]

If you site in at sea level, and then come to a altitude of say 10k then you will be a smidge high depending on cal., grains, etc. it is not real signifcant at 100 or so yards, but beyond that it can make a difference. Not sure if velocity is a factor. Just going on personal info from shooting up here at 10k+ and then going to FL

[theGinsue]

spleify - Yes, and no. Thr POI will be different, not necessarily lower. There ar a lot of variable to consider. Even if all other options were controlled, to simply state that the change in altitude will cause the POI to be lower" to much too simplified

If you are a big game hunter here in CO, I'm sure that you have heard that, in addition to shooting your hunting rifle throughout the year, you should also try to shoot your rifle at a similar altiude and preferably nearby your actual hunting location.

[trlcavscout]

spleify - Yes, and no. Thr POI will be different, not necessarily lower. There ar a lot of variable to consider. Even if all other options were controlled, to simply state that the change in altitude will cause the POI to be lower" to much too simplified

If you are a big game hunter here in CO, I'm sure that you have heard that, in addition to shooting your hunting rifle throughout the year, you should also try to shoot your rifle at a similar altiude and preferably nearby your actual hunting location.

Exactly. If your sighted for 2k at 80 degrees F and you go hunt at 10k+ and 20 degrees F it could be a big difference, plus other variables like your rifle, the ammo etc. Even if 100yds is your max distance I would check your sights when you get there. I have seen a 2-3" difference just changing a couple k feet and 20 degrees or so even with similar humidity. Also a crosswind will have a different effect in different conditions. And like Ginsue said it doesnt always change the way you think or hope it will.

[funkfool]

I have been looking into this and have found this to help...
http://www.jbmballistics.com/calculations/calculations.shtml
And one (of many suggested) books:
http://www.appliedballisticsllc.com/index_files/Book.htm

[Not_A_Llama]

I was going to ask about available oxygen to feed the explosion, but it seems like since the case is sealed, it wouldn't really be an issue. Maybe less flash though?

Gunpowder contains its own oxidizer. Guns work in space - the Soviets had an AA cannon mounted on one of their stations.

Less air density means your bullet is subjected to less drag. It's not a lot, though, until your distances get pretty long.

[Irving]

I once saw an episode of Cowboy Beebop where the guy bungles a space walk so he pulls a Glock out of his waste band and shoots in the opposite direction to push himself back toward the ship. I guess it would work then. :)

[Graves]

I once saw an episode of Cowboy Beebop where the guy bungles a space walk so he pulls a Glock out of his waste band and shoots in the opposite direction to push himself back toward the ship. I guess it would work then. :)

He'd have died on impact if it was a G20 after he hit the ship.

[Irving]

10mm. Not even safe in space.




lol

[Tim K]

On a typical hunting cartridge like the .308, the point of impact shift is only 1" at 300 yards going from sea level to 9,000ft., everything else being equal. The effect gets larger as range increases. For example, the same .308 at sea level is going 1050fps at 1000 yards and is probably unstable. At 9,000ft, velocity is north of 1,300fps, still supersonic, and still stable.

A bigger deal might be the reduced temperature going up from sea level. Most powders are temperature sensitive giving less pressure and velocity as temp decreases. Depending on the powder type and temperature change, this effect might swamp any issues due to air density.

Note, increasing humidity decreases air density, counter to what it feels like to us. So, high, hot, and humid lead to best ballistic performance. Low, cold and dry are worst.

[spleify]

Very interesting stuff everyone. Thanks for the tips.

So for the average shooter, these variations likely will not make much difference. But to the competition shooter, or trained and skilled sniper I would assume all of the factors would make a big difference. Correct?

[KFinn]

There is one show that keeps coming to mind that I watched on the History channel. It was Sniper something. I have it on my DVR at home. Its not Modern Sniper. But anway, it is a 2 hour show dedicated to what they thought some of the best confirmed Sniper shots that have been made.

The one that keeps popping to mind is a candaian sniper in Afgan with the Baret 50cal. Made I think a mile an half long kill shot. one of the voice over comments was somethign to the effect of; The success of the shot at that range may have been some of the partial contributions of the higher altitude and the very hot day. All decreasing the drag because.

I recommend checking out the entire show to see some really cool shit.

[KFinn]

Here it is.... the whole show focused on several shots. I think there were like 5 or 6 or so that they covered in the video and then tried to recreate the shot today using similar setup/equip/enviornment.

Sniper: Inside the Crosshairs
http://shop.history.com/detail.php?p=254215

[Irving]

I watched that show twice, back to back.

[spleify]

I did watch that show too. I will watch it again as I'm sure I missed a loyt of it.

Thanks

[sniper7]

I have been looking into this and have found this to help...
http://www.jbmballistics.com/calculations/calculations.shtml
And one (of many suggested) books:
http://www.appliedballisticsllc.com/index_files/Book.htm


looks like good info from the parts I looked at, thanks for the links

[sniper7]

Here it is.... the whole show focused on several shots. I think there were like 5 or 6 or so that they covered in the video and then tried to recreate the shot today using similar setup/equip/enviornment.

Sniper: Inside the Crosshairs
http://shop.history.com/detail.php?p=254215

sweet!

[Troublco]

He'd have died on impact if it was a G20 after he hit the ship.


10mm. Not even safe in space. lol

Maybe ya'll just need to man up so's you can shoot a REAL gun.......[ROFL1]

[SA Friday]

Yes, gunpowder would work in space as it has it's own oxidizer, but the gun itself wouldn't. At that temp, anything resembling lubricant would be frozen solid, and many of the metals involved could become overly brittle and fail upon ignition.

[sniper7]

Yes, gunpowder would work in space as it has it's own oxidizer, but the gun itself wouldn't. At that temp, anything resembling lubricant would be frozen solid, and many of the metals involved could become overly brittle and fail upon ignition.


unless you have a glock....oh wait, nevermind, thats right they blow up even here on earth so they wouldn't stand a chance in space![ROFL3]

[Irving]

Yes, gunpowder would work in space as it has it's own oxidizer, but the gun itself wouldn't. At that temp, anything resembling lubricant would be frozen solid, and many of the metals involved could become overly brittle and fail upon ignition.


Sounds like we should have Mythbusters fire some guns in vacuum. That way there would be no oxygen, but without the low temperatures of space. No hearing protection required!

[funkfool]

Here it is.... the whole show focused on several shots. I think there were like 5 or 6 or so that they covered in the video and then tried to recreate the shot today using similar setup/equip/enviornment.

Sniper: Inside the Crosshairs
http://shop.history.com/detail.php?p=254215
This is a great show... have it on the DVR too.

[Mtn.man]

Here's some shots at altitude and long range

http://www.break.com/usercontent/2009/8/picking-off-the-taliban-1144565.html

[edjobsman]

I was going to ask about available oxygen to feed the explosion, but it seems like since the case is sealed, it wouldn't really be an issue. Maybe less flash though?

I remember doing an experiment in chemistry lab were we burned this chemical in air. The big surprise for many of us was that the resulting compound was heavier, a lot heavier than the starting chemical. That means that a weigh-able amount of O2 combined with the chemical resulting in an oxide.

Here is the part that I don't have any data on: I don't know how much the O2 weighs in a given cartridge and I don't know how much O2 would be required for a chemical reaction involving gun powder, if any. There can't be much O2 in the cartridge; I would guess not enough to power a chemical reaction powerful enough to fire a bullet 100s of yards. I can't imagine being able to weigh the cartridge O2 even with a very sensitive analytical balance and a method to do so. Therefore my guess is the oxidizer is not in the air in the cartridge, but rather in the powder itself or it gets sucked in down the barrel as the bullet comes out, which doesn't seem right because I think the reaction would be too slow (have you ever poured smokeless powder on the ground and lit it?) and might interfere with the forward motion of the bullet. Also if it were atmospheric oxygen, I bet there would be a lot more ash or soot (like the stuff we weighd in the cubicle in the lab) after the reaction. That would equal a lot dirty barrels. I realize that the air pressure caused by the "burning" powder might blast some of the dirt out if enough pressure could be generated. What's in gun powder? Sulfur, charcoal, salt peter (Capt. Kirk's recipe). I bet one of those is supplier of oxygen.

Sorry - verbiage. Hey I like to write...