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Kestrel meters


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I was looking at the 3500 too AFH because it can read humidity but from my research humidity is not gonna effect the ballistics of my 175gn 308 at 1000yd to much maybe around .3-.4 moa adjustment from a 0-100% humidity change. where i live the average humidity is around 65% and normally veries from 40-80% so i guess i would only have to correct maybe around .1-.2 moa.so I thought I'd save some money with the 2500 but I could be wrong cus I never have shot to that range yet so far. What do you all notice when correcting for humidity?

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I was looking at the 3500 too AFH because it can read humidity but from my research humidity is not gonna effect the ballistics...

I've had long discussions over this with a number of experts, including Brad Millard (JBM Ballistics). Basically, you need either temperature, pressure, and humidity at your location or you need density altitude (which is a calculated value based on the other three). Humidity is such a small factor that it can be ignored (generally set to 50%).

Pressure becomes is the critical factor. If you have the absolute pressure (as measured at your location), then you don't need altitude. If all you have is the corrected pressure (from a weather station), then you also need altitude. This is where the Kestrel comes in. Meters like the 2500 on up will give you absolute pressure, which allows you to ignore altitude.

Some meters will calculate density altitude, and if you have ballistic software that will use it, that's simpler than pressure and temperature. If you are using charts rather than ballistic software, that can make quite a bit of difference. It's up to you to decide which is the better solution for you.

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I bought the 4000BT to get DA, and bluetooth (BT wasn't as helpful as I thought.)

I like using DA, it is easier to input one number, and I can make range cards for various DA readings instead of needing 3 metrics and then relying on electronics to spit out my dope.

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I was looking at the 3500 too AFH because it can read humidity but from my research humidity is not gonna effect the ballistics...

I've had long discussions over this with a number of experts, including Brad Millard (JBM Ballistics). Basically, you need either temperature, pressure, and humidity at your location or you need density altitude (which is a calculated value based on the other three). Humidity is such a small factor that it can be ignored (generally set to 50%).

Pressure becomes is the critical factor. If you have the absolute pressure (as measured at your location), then you don't need altitude. If all you have is the corrected pressure (from a weather station), then you also need altitude. This is where the Kestrel comes in. Meters like the 2500 on up will give you absolute pressure, which allows you to ignore altitude.

Some meters will calculate density altitude, and if you have ballistic software that will use it, that's simpler than pressure and temperature. If you are using charts rather than ballistic software, that can make quite a bit of difference. It's up to you to decide which is the better solution for you.

Ok thanks for the info although I have a few question. I will be using dope charts to make my correction rather than ballistic software because I'd rather learn and know how to make my correction then have a computer tell me the corrections. I probably will end up with ballistic software later down the road after I get the hang of doing my own corrections. As far as I understand berometric pressure changes in correlation with altitude. The effect on ballistic is caused by the bero pressure,temp and slightly humidity and not the altitude. Density altitude is a correction of pressure,altitude and humidity from a standard temp. So pretty much a DA meter measures press,temp and humidity corrects for and changes and gives u a true pressure and altitude reading? So for an example if your 5000 feet up in elevation and the temp is colder then normal standard, the air pressure is going to be more dense making the climate as if u were in a lower altitude. Am I grasping this correctly? Not sure I completely understand the benefit of having say a kestrel 4000 that measures DA vs a 2500 that reads berometric press and temp other then it doing an equation for you making it easier. Being in my shoes relative long distance noobie and using charts right now not ballistic software what would be the better choice?

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There is absolute (station) pressure and reported barometric pressure. Absolute is the pressure reading at your specific location. Barometric pressure is a pressure reading corrected to sea level - this is what you would get from a weather station. If you use the former, then you don't need altitude, whereas you do with the latter.

Many published data cards ignore pressure and just use altitude instead.

Are you going to try and create your own data cards?

Edited by Graham Smith
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Yes I have started to take down information to make my own data cards. When reading about the kestrel meters they all say they measure barometric pressure (what I thought is atmospheric pressure measured through a barometer)like grandpa's old mercury barometer when atmospheric pressure rises it pushes down on the barometer pushing the mercury up the tube so u can gather the

in hg reading. Being that I thought their barometric reading was an actual reading at the spot and not from a weather station. Is there a separate setting on the kestrel meters for absolute pressure?

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A reading you take on the spot, that is not corrected, is called station pressure or absolute pressure. A pressure that you get from a weather station is corrected (to sea level) pressure or more often just barometric pressure.

Both readings are often called barometric pressure and to add confusion to the mix, the weather station pressure is sometimes mislabeled as station pressure with the assumption that it is the absolute pressure at the location of the weather station. Which if you are watching Eye-Witness Weather with Les Nessman, is the 3rd floor of the Flimm Building in downtown Cincinnati.

Handheld weather meters are really more simple than you might think. Most only measure temperature and absolute pressure. If they include altitude, it's usually estimated based on pressure. Have a look at the instructions for the Kestrel 2500

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You might consider spending a few extra bucks and getting into the 4000 series meters. You may not want density Altitude now, but you may in the future. It certainly can speed things up.

Could you elaborate?

I've seen this mentioned before and never entirely understood how. I know that it's possible to make up DOPE charts using DA, which are simpler to use once made up, but none of the ballistic software I have looked use it.

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Density altitude also accounts for the air temprature as it relates ballisticly. You still need to account for the temprature as it relates to your powder burn rate and the effect on your muzzle velocity, but DA is a single number that is comprised of altitude, barrometric pressure, temprature, and humidity. You make a card for your load at various different DA's and then pick the card that is most appropriate at the time of the shot. JBM is what I use, pretty straight forward, a bit of time spent google reading and you will most likeley be a pro. It will take far longer for you to type up the cards and laminate them than calculate the actual values. With a meter that acurat.ey reads DA, accurate BC on your bullets (Litz), the correct ballistic model (G7), the only real obstacle is getting a good muzzle velocity.

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Here is what confuses me about density altitude... You say:

DA is a single number that is comprised of altitude, barrometric pressure, temprature, and humidity...

But Brad at JBM told me in an email about the DA on a Kestrel:

Density altitude should be the same as the density calculated from temperature pressure and humidity, if they measure the three right (that's probably what the Kestrel does anyway). The problem I have with density altitude is that people tend to forget that the solution depends on temperature independent of density. So you either need temperature, pressure and humidity OR density altitude, temperature and humidity. (Humidity is a small correction and can generally be left out). If you have temperature, absolute pressure and humidity, I couldn't care less about the altitude. If you have a corrected pressure, then you need the altitude too.

Somewhere in all of this, there is something that getting missed. As I read the email from Brad, you need temperature regardless of whether you are using DA or not. That would seem to go along with what you were saying about temp and muzzle velocity. If that's the case, then it would seem that regardless of whether you are using absolute pressure or DA, you still need Temp (humidity can be set at 50% for all cases and ignored).

It's probably because I have not had a reason to use DA, but I'm still not sure what advantage it gives you.

Edited by Graham Smith
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Density altitude also accounts for the air temprature as it relates ballisticly. You still need to account for the temprature as it relates to your powder burn rate and the effect on your muzzle velocity, but DA is a single number that is comprised of altitude, barrometric pressure, temprature, and humidity. You make a card for your load at various different DA's and then pick the card that is most appropriate at the time of the shot. JBM is what I use, pretty straight forward, a bit of time spent google reading and you will most likeley be a pro. It will take far longer for you to type up the cards and laminate them than calculate the actual values. With a meter that acurat.ey reads DA, accurate BC on your bullets (Litz), the correct ballistic model (G7), the only real obstacle is getting a good muzzle velocity.

Thanks for the advise. I was looking at the JBM DA trajectory card program and kinda get what your saying by adding the Info to the program it prints out a card with the DA that u chose along with different temp correction for that DA. After you have that card when u get the DA and temp from the kestrel u just reverence to the card for the drop. But here is where I'm a little confused I put the same information in the regular trajectory program and the drop reading are .5 MIL less @ 1000 then the DA card. I noticed that the DA program doesn't ask for Humidity readings or pressure readings is this where the difference is coming from? I'm also a little fuzzy on what the different ballistic models are (G1)-(G7) and what the difference is between the normal BC of say a 175gn smk compared to 175gn (Litz) could u explain?

Thanks

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Histate...Kestral meters are great and no matter which model you buy you won't be disappointed.

Temperature is NOT a factor in ballistics UNTIL you get out past 500 yards or so.

Anyone not believing this can spend the dime on a phone call out to Jeff Hoffman @ Black Hills Ammunition to get told the same thing. If you ask nice he may even send you a copy of the article he wrote on the subject for the publication "Sniper".

With the "old" powders temp WAS a factor....many years ago.

The new propellants out there in both reloaded and factory ammo are not temperature sensitive and no correction for temp needs to be made as long as you're shooting less than 500 yards.

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Thanks JK yah I'm probably gonna get the 4000nv to upgrade my old meters it will also be nice to have one meter that will be able to accomplish the task that I need instead of carrying around a bunch of separate meters. yah I realize that about temp and I'm pretty lucky that where I live there isn't to much temp change, which is bad at the same time because I don't get to experience that aspect. I was at the range this past weekend shooting out to 500 with pretty stiff winds the weather report said 15-25 mph but I don't have a Anemometer so I had to guesstimate the wind at my location.that's another reason why I wanted to pick up a kestrel but despite all that's i was pretty happy that my guestimation worked and was able to hit the target

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i know this may sound stupid, but i was thinking until you get above 2000-2500 feet that altitude was not a big factor. (in general)

i also know/understand it depends on the results the shooter is looking for.

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