Not sure if this is the right place to ask, but looking for information on altitude changes in dope. Working on three guns for an elk hunt. Have my dope for 700’ ASL. All guns (300wm, 338wm & 33Nosler) are shooting 210gr bullets at about 3000fps. What will happen when we go to 8000 or 10,000’ ASL?
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Altitude Effects
- Thread starter Fgcook
- Start date
download any ballistic app on your phone or any online ballistic calculator and change those parameters and see what happens to your dope
Easiest thing to do is put different altitudes in your ballistic calculator, print the charts and look at the differences at the ranges you intend to shoot. I use http://www.jbmballistics.com/ballistics/calculators/calculators.shtml for this kind of experiment.
For ground hogs and stuff you might shoot just for fun it can get you more hits. For me, at the distances I would shoot big game its not going to make much difference. I might be able to ring a plate all day long at 1125y but I'de never take a shot at an elk at even half that range. My brother and nephew went out west last year elk hunting. A group of California hunters staying at the same hotel were at the bar bragging about their 1200y kill. Only took them 28 shots, and they hit it 14 times.
For ground hogs and stuff you might shoot just for fun it can get you more hits. For me, at the distances I would shoot big game its not going to make much difference. I might be able to ring a plate all day long at 1125y but I'de never take a shot at an elk at even half that range. My brother and nephew went out west last year elk hunting. A group of California hunters staying at the same hotel were at the bar bragging about their 1200y kill. Only took them 28 shots, and they hit it 14 times.
People like that need to be taken out back and beaten.
D
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What they said...get a Kestrel that will give you Density Altitude data, and an app (like Strelok, Applied Ballistics, etc) and it will give you the information you need for varying elevations.
D
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Guys, don't over think it. He doesn't need to buy anything, he can use JBM for free and write it down on a card. It's not rocket surgery.
Correct - that's the simple and free method, and I highly recommend it, but will not be as precise as getting the actual density altitude for your specific conditions. Fgcook: You'll have to decide if it worth it to use actual condition values, or just get close using theoretical values. If you're only shooting 500-600 yards maximum your margin of error will be pretty large, but if you're shooting smaller targets at longer range, it will make more of a difference.
Edited to add: When I zeroed my rifle, my density altitude was 3000ft different than my physical altitude, and this last weekend I shot at an elevation that was 6500ft higher than my physical zero elevation, and my density altitude was 2000ft higher than that. If those differences in density altitude would have stacked, I would have had a 5000ft variance in air density and at long ranges that would have caused a big miss.
Edited to add: When I zeroed my rifle, my density altitude was 3000ft different than my physical altitude, and this last weekend I shot at an elevation that was 6500ft higher than my physical zero elevation, and my density altitude was 2000ft higher than that. If those differences in density altitude would have stacked, I would have had a 5000ft variance in air density and at long ranges that would have caused a big miss.
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Asking because I'm a relative newbie but could you not get an approximate elevation at your intended shooting location from Google maps, and with that, run and print a few data cards from JBM with anticipated temps?
D
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Yep, you could do that very thing. That is how it was done before ballistic apps (but we used USGS maps). The station pressure won't vary enough from standard in a given location to make enough difference to notice. Temperature will affect your powder burn rate, so you need to be aware of those effects, but again, a small difference.
Combine that with the experience of sending rounds downrange and you have a system that never stops working because of software bugs, dead batteries, or being dropped and broken.
I'd like to agree here too. >Just as I typed that it sounds f'd up.. I am leaving it as, because it shows how poorly I communicate.<
Re typed.
I agree here too and like what you are saying.
I can't tell you how many time I have been at a mach (I am using that example because a lot of PR shooters are in one location) and guys whip out their Kestrels to check the dope over and over at every station.
As Skookum pointed out, the variance of SP throughout the day, much less day to day, in the same location really doesn't vary enough do much in that 1000 and under range. ( I am not talking about climbing a huge mountain and hiking for 20 hours). So his suggestion of the maps and planning using station, is a solid plan.
Temp: Running temp stable power you also need a way bigger temp swing than people think. 10° - 20° isn't a deal killer. If the two temps are extreme, maybe run 2 temps the expect low and high. Then only write down the only drop changes at distances they start to make a difference. That will help provide confidence what you need to do for the temps in the middle.
Antidotal: At a club match I've run the same dope cards and been the top scorer winter and sumer.. NEVER changing them. Yes, I'll agree when it is 40° I'll add .1th at the longer ranges and when it is 105° I'll take a .1th off my 70° dope acrd.. but it works fairly solidly at 60° thru about 85° out to about 1K. I am not saying this is better, than accounting for all the proper variables, just illustrating that sometimes we get analysis paralysis rather than shoot.
D
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This discussion brings back an old formula to memory.
For your round, you take a constant ( .025 for something like 308 with a .500 G1 BC, or .015 for something like a 6.5 with a .700 G1 BC). You multiply the constant by the altitude change in 1000's of feet. Then multiply the distance in 100's of yards by 0.1 per 100 yards. This gives the percent of change at that distance from your baseline dope.
Probably not the way anyone would be inclined to do it these days, but there it is.
For your round, you take a constant ( .025 for something like 308 with a .500 G1 BC, or .015 for something like a 6.5 with a .700 G1 BC). You multiply the constant by the altitude change in 1000's of feet. Then multiply the distance in 100's of yards by 0.1 per 100 yards. This gives the percent of change at that distance from your baseline dope.
Probably not the way anyone would be inclined to do it these days, but there it is.
If you have to ask this question, it isn't going to matter to you, as you should not be taking a shot long enough to matter at any increased elevation on a big game animal.
That said, do as diverdon said and get on JBM and just use the different altitudes to see how far out your shots begin to vary and by how much to practice at long range. You might want to ring a lot of steel in a lot of conditions before you turn that practice on an animal.
That said, do as diverdon said and get on JBM and just use the different altitudes to see how far out your shots begin to vary and by how much to practice at long range. You might want to ring a lot of steel in a lot of conditions before you turn that practice on an animal.
I'm still getting my head around the altitude difference moving from NY (800ftASL) to AZ (4350ASL).
Wunderground lists my Air Density at 29.92in hg, and the 4DOF/Hornady fills in that precise value for the program when I enter the 4350ASL value. According to this my 260/143 ELD-X 2750fps (conservative velocity estimate, 28" barrel) load crosses below 1300fps/35-ish MOA drop w/100yd zero/560ft-lb energy just a tad past 1100yd. Unless there's a good reason otherwise, I'm going to consider that distance and drop to be my max range for inanimate targets. IMHO, odds favor a higher impact.
If this is wrong, how come?
Distances here can go long, with literally over ten miles of visibility in some areas. I'll not be making shots over 200yd on large game animals, if at all, because I'm just not up for retrieving heavy animals at longer distances these days.
I think that for shooting beyond 500yd, it probably makes more sense to move the zero distance from 100yd to 200yd.
Greg
Wunderground lists my Air Density at 29.92in hg, and the 4DOF/Hornady fills in that precise value for the program when I enter the 4350ASL value. According to this my 260/143 ELD-X 2750fps (conservative velocity estimate, 28" barrel) load crosses below 1300fps/35-ish MOA drop w/100yd zero/560ft-lb energy just a tad past 1100yd. Unless there's a good reason otherwise, I'm going to consider that distance and drop to be my max range for inanimate targets. IMHO, odds favor a higher impact.
If this is wrong, how come?
Distances here can go long, with literally over ten miles of visibility in some areas. I'll not be making shots over 200yd on large game animals, if at all, because I'm just not up for retrieving heavy animals at longer distances these days.
I think that for shooting beyond 500yd, it probably makes more sense to move the zero distance from 100yd to 200yd.
Greg
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D
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Wunderground isn't giving you actual air density (station pressure) it is giving you barometric pressure, which is adjusted to reflect arelative variation from standard pressure at your altitude. Your actual station pressure is going to hover somewhere around 25.7 Hg.
If I misunderstood the post and you already knew that, then please disregard.
Good shooting
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There is zero benifit when using our subtensioned reticles to zero at 200 for a 500 yard shot.
What it does do:
1- create more hold unders.
2- make it harder for some people to get a perfect zero with environmental effects (although 200 really in’t that bad)
3- But change normal day to day dope that one might use and practice daily for similar cartridges. (My pet pev)
Just my simplified take on reported baro:
The Baro reported or adjusted, has a important use outside what we do. It is more important in forecasting weather and communication the conditions across distances to help create an easily baseline.
For flying it's useful, but for shooting it is not very useful, but some shooters continue to use it. DA, is great for communicating, provides one number that lets us all understand the conditions effecting others drop, but it needs a solver to do it quickly and more complicated to remember all the combinations that provide the same DAs.
With as much as we spend on our weopons systems, an much as it cost to pull the trigger and drive to our locations it is beyond my simple brain why all shooters do not use the true barometric pressure or station pressure to create their dope.
Forget the Kestrel if money is short. How about a cheap Casio that tells time every day, but provides true Baro or even an $84 BallisticsARC weather/wind device?
If traveling look up the elevation and quickly convert to actual Baro, not a hard thing to do.
Using adjusted barrow and elevation by pinging the local weather station in your app is full of compromises and repeating that always trying to find the DA isn’t much better. This is especially problematic in the field and working with dope cards.
Edited to try to make more clear
The Baro reported or adjusted, has a important use outside what we do. It is more important in forecasting weather and communication the conditions across distances to help create an easily baseline.
For flying it's useful, but for shooting it is not very useful, but some shooters continue to use it. DA, is great for communicating, provides one number that lets us all understand the conditions effecting others drop, but it needs a solver to do it quickly and more complicated to remember all the combinations that provide the same DAs.
With as much as we spend on our weopons systems, an much as it cost to pull the trigger and drive to our locations it is beyond my simple brain why all shooters do not use the true barometric pressure or station pressure to create their dope.
Forget the Kestrel if money is short. How about a cheap Casio that tells time every day, but provides true Baro or even an $84 BallisticsARC weather/wind device?
If traveling look up the elevation and quickly convert to actual Baro, not a hard thing to do.
Using adjusted barrow and elevation by pinging the local weather station in your app is full of compromises and repeating that always trying to find the DA isn’t much better. This is especially problematic in the field and working with dope cards.
Edited to try to make more clear
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Not sure what you're saying here, but I'm a private, instrument rated pilot and both barometric pressure and density altitude are extremely important to aviation. The former to maintain an accurate altimeter and the latter to accurately predict takeoff and climb performance. People have lost their lives, and killed innocents, due to not paying attention to either of those factors.
Yes, we are saying the same thing, air density is important for both flying and shooting. but was not clear What I am attempting to say is that for shooting, working in adjusted baro then trying to covert to DA is to long and convoluted for shooting. Pilots are are getting correct local info, have instrumentation/tools, that field shooters don't.
I'll edit the typo// even this response had to be edited because I could understand my own Siri post
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Yeah, we agree. Having learned to fly before I learned to shoot, I wondered why shooters wanted to deal with a derived value rather than entering the easily obtainable raw data (temp/baro press/altitude) and pressing GO
In my first post it sounds like I poo-poo the effects of altitude. This is not the case. I simply mean that at this point in the shooters (OP) journey of learning how to shoot long range, he should not be taking shots that altitude, temp and pressure variations have a large effect on.
One of my issues with using DA in shooting is that a lot of people confuse air density with density altitude. Or, at least how to read it. High air density is low altitude, and low air density is high altitude. High density altitude is high altitude. Meaning "density altitude" needs to be understood as altitude not density of the air. If shooters understand that then use it.
308pirate, I'm an aircraft mechanic and we deal with setting and checking these instruments all the time, and yes they are IMPORTANT!
I think any shooting teacher needs to imbue the importance of altitude effects, as well as temp and pressure, on long range shooting. DA is a great way to combine the factors necessary to calculate a long shot. But, many new shooters, and teachers alike don't understand how to use it or arrive at it. But, it's okay if it remains broken down in it's raw data factors so shooters and teachers alike can grasp what all the factors mean.
As an example, I was at a shoot out to 1600 yds at 2,000 ASL It was cold and cloudy. What I didn't know was we had a high pressure front moving in. I couldn't even see where the shots were going. I was talking with other shooters and one was a pilot and he said, the baro was 30.2 when he flew in earlier. And, that was not corrected. I adjusted for this unusually high pressure and my shots started hitting. It took 75 moa to reach the target that day. Conversely, on a beautiful sunny Nevada day at 4000' ASL a couple months later it only took 59 moa. Same load batch, just different weather. Added: And altitude.
So, in retrospect using standard altitude variation didn't work that morning, because of the weather front change. later it worked fine at a higher altitude. Always good to get as close as you can in raw data.
One of my issues with using DA in shooting is that a lot of people confuse air density with density altitude. Or, at least how to read it. High air density is low altitude, and low air density is high altitude. High density altitude is high altitude. Meaning "density altitude" needs to be understood as altitude not density of the air. If shooters understand that then use it.
308pirate, I'm an aircraft mechanic and we deal with setting and checking these instruments all the time, and yes they are IMPORTANT!
I think any shooting teacher needs to imbue the importance of altitude effects, as well as temp and pressure, on long range shooting. DA is a great way to combine the factors necessary to calculate a long shot. But, many new shooters, and teachers alike don't understand how to use it or arrive at it. But, it's okay if it remains broken down in it's raw data factors so shooters and teachers alike can grasp what all the factors mean.
As an example, I was at a shoot out to 1600 yds at 2,000 ASL It was cold and cloudy. What I didn't know was we had a high pressure front moving in. I couldn't even see where the shots were going. I was talking with other shooters and one was a pilot and he said, the baro was 30.2 when he flew in earlier. And, that was not corrected. I adjusted for this unusually high pressure and my shots started hitting. It took 75 moa to reach the target that day. Conversely, on a beautiful sunny Nevada day at 4000' ASL a couple months later it only took 59 moa. Same load batch, just different weather. Added: And altitude.
So, in retrospect using standard altitude variation didn't work that morning, because of the weather front change. later it worked fine at a higher altitude. Always good to get as close as you can in raw data.
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No, you understood my post fine. I had earlier looked up an altitude/density chart, which indicated that my local air density was about 85% that of sea level, had applied that to sea level nominal density and then plugged it into the HDY 4DOF. The resulting drops and velocities were like something out of science fiction and I ended up doing the head scratch boogie.
If that was not science fiction, then the 28" 260 barrel is something of a Wunderbuss at my altitude.
I will substitute the the 25.7 value and see what she renders.
Thanks plenty for your insight.
Greg
PS Ummm..., WoW!
Using a known 2800fps MV from the 140 A -Max, I replotted the trajectory. I had to stretch the max distance to 1600yd before I could see a velocity below 1100fps (actually 1099).
That's, well, spooky.
At the 1600yd point, it's 1099fps, 59.85 MOA, and 383 ft-lb.
1353fps, 40.41MOA, and 581ft-lb at 1300yd.
No wonder I have some issues breathing OK in the morning. S'OK, I just take my Lasix and all is fine within a half hour.
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Maybe I am misunderstanding your information. I also often shoot in the high desert.
Let’s leave temp off the table because if it suddenly went from 80 to 40 and started hailing we’d change the temp setting
. Let’s leave out hurricanes and Typhoons that actually can change pressure by 3 inches.So when a storm moved while you were shooting in the Fallon Sink area that is 25.5inHg, how much pressure chance are you seeing?
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D
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The problems I have with using DA are:
A. ( Just as you mentioned ) It confuses people.
B. Temperature matters to a firing solution because it affects powder burn rate and therefore velocity. Maybe your Kestrel, or whatever, is making that calculation for you as it extracts that info from the DA equation...I don't know, but one way or the other, it means that the shooter has no idea that it is going on and can't learn anything from it and can't check it.
C. Relating to "B" in the above statement, temp sensitivity is different for every cartridge / bullet / powder combination. One number cannot accurately reflect every combination.
Good shooting
The front moving out, high pressure moving in, was in Sandpoint, ID. I later shot in Fallon, where the standard elevation change applied. Sorry, "later" = 3 months later at a different shoot.Maybe I am misunderstanding your information. I also often shoot in the high desert.
Let’s leave temp off the table because if it suddenly went from 80 to 40 and started hailing we’d change the temp setting
So when a storm moved while you were shooting in the Fallon Sink area that is 25.5inHg, how much pressure chance are you seeing?
Added: and obviously a different altitude.
I'm only differentiating temp as a raw data factor. If you use DA, then it's a part of that too.
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Gotcha -
Not a reply to you, just putting daily pressure in perspective for the thread:
My point about not making to big a deal once you “ know” the Station Pressure (true baro) and shooting the 1000y and under thing, is that during the day, even day to day at the same spot, pressure changes less than many shooters think.
Here are the record (adjusted) high and lows for Reno NV over 100 years of recording crazy storms: (I had to google that)
Record high: 1/3/1919 30.92
Record Low: 1/21/2010 28.91
That's only +/- 1inHg over 100 years., any many of those conditions there is no way one would shoot Long range.
So lets, just assume that we are shooting at 25.5 at our 1000 yard target, a huge storm front is coming maybe as big as there has been. Within minutes, it drops a full inch (not likely) so now we are at 24.5.. Using my 6.5, I have to take off .1mil, probably not enough to sale over most targets.
All that said, realistic changes might not even be .2 inHg during the day. In the situation above, that makes .02 mils drop change.. No idea how I would adjust my scope
So if we use basic information gathering and use non-adjusted baro AKA station pressure like Skookum pointed out, it is easier to separate key contributors to velocity change.
This is just my POV, but hell, I miss enough and don't need more confusion trying to figure out what parts of DA are doing what.. If I can just set the station, watch the temps, but focused more on WIND and optical issues, I find shooting more fun and productive.
PS if you are shooting in a Tornado, Hurricane or Typhoon -- adjust your station pressure often -- lol
One might want to adjust their brainset...it don't function well in weather like that.??Gotcha -
Not a reply to you, just putting daily pressure in perspective for the thread:
My point about not making to big a deal once you “ know” the Station Pressure (true baro) and shooting the 1000y and under thing, is that during the day, even day to day at the same spot, pressure changes less than many shooters think.
Here are the record (adjusted) high and lows for Reno NV over 100 years of recording crazy storms: (I had to google that)
Record high: 1/3/1919 30.92
Record Low: 1/21/2010 28.91
That's only +/- 1inHg over 100 years., any many of those conditions there is no way one would shoot Long range.
So lets, just assume that we are shooting at 25.5 at our 1000 yard target, a huge storm front is coming maybe as big as there has been. Within minutes, it drops a full inch (not likely) so now we are at 24.5.. Using my 6.5, I have to take off .1mil, probably not enough to sale over most targets.
All that said, realistic changes might not even be .2 inHg during the day. In the situation above, that makes .02 mils drop change.. No idea how I would adjust my scope
So if we use basic information gathering and use non-adjusted baro AKA station pressure like Skookum pointed out, it is easier to separate key contributors to velocity change.
This is just my POV, but hell, I miss enough and don't need more confusion trying to figure out what parts of DA are doing what.. If I can just set the station, watch the temps, but focused more on WIND and optical issues, I find shooting more fun and productive.
PS if you are shooting in a Tornado, Hurricane or Typhoon -- adjust your station pressure often -- lol
Free system that will really help with all the data and building a firing solution. 8 agree with everyone that you cant depend on electronics.
1stshot.org
FYI here is my arm board range card for 23inHg
Is 40 right now and about 20mph near Laramie.
Note I generally use a 6mph mil wind but in Wyoming, it seems 12-15 is a normal low wind often above 20. Dang I thought we had it bad, but those guys in Wyoming really deal with wind.
Two small charts cover most of the year. ELR, is better as a single solution
Is 40 right now and about 20mph near Laramie.
Note I generally use a 6mph mil wind but in Wyoming, it seems 12-15 is a normal low wind
often above 20. Dang I thought we had it bad, but those guys in Wyoming really deal with wind.
Two small charts cover most of the year. ELR, is better as a single solution
Going from 700ft to 8,000 or 10,000ft is not just about guns and ballistics. It's also about fitness and altitude acclimation. If you're not ready to cope with a nearly 10,000ft increase an altitude, activity will be seriously curtailed, and could even be life threatening for some.
I lived at about 800ft until coming to Arizona, where I now live at 4350ft. It was several weeks before I could get about and perform tasks without rapid fatigue and general weakness. Even a year after, going up to Mount Lemmon at 8,000ft imposed such a severe burden on my breathing that I had to rapidly retire back to the Desert basin level before could breathe right again.
I qualify this info with full disclosure, I have a significant heart condition, combined with COPD. But this does not mean one cannot still accommodate; I get around fine at 4350ft right now, and with some gradual acclimation, I believe I could increase that capacity by several more thousand.
The point I'm trying to make is that vast changes in altitude have a price, and that it may involve extra time acclimating. Even Olympic athletes need to acclimate, sometimes by several weeks, when engaging in physical challenges well above sea level.
So think about this an maybe see if you can work some acclimation into your plan.
Greg
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