## Altitude To Atmo Pressure & Free Recoil Calculator Spreadsheet

Started by ThunderDownUnder, March 29, 2011, 08:11:10 AM

#### ThunderDownUnder

As I'm interested in all things that contribute to a better shooting outcome, I have put together a new spreadsheet that combines converting Altitude to Atmospheric Pressure (ICAO Standard) and a Free Recoil calculator spreadsheet. At the moment the spreadsheet does not use BfX functions but it would obviously benefit from unit conversion being made available. I would like to here from anyone that finds this useful and would like it displayed differently using BfX. Feel free to improve on this initial attempt at a useful spreadsheet!

Ian

in the beginning bfc_c had an additional paramerter h for height. I dropped it because I thought it would be easier and accurater to measure the pressure and humidity at the shooting range. Is this theory from somebody living at +1 meter, the highest point in the area?

#### ThunderDownUnder

#2
I'm guessing the rifle ranges in the Netherlands are not exactly at high altitudes. I just Googled and discovered Vaalserberg is the highest hill and its 322.7m high. Australia likewise is pretty flat and a quick calc for 2 local rifle ranges I use puts one at approx 400m and another at 4m above sea level. Using BfX functions I discover that for one of my rifle loadings the atmospheric air pressure may give approx 0.5 moa difference at 1000 yards for this variation in altitude (4 to 400m). Humidity has even less of an effect on the trajectory. Maybe the free recoil calculator provides a measure of something that could effect the accuracy more than a 400m altitude change?

Ian

ha ha, Vaalserberg (meaning "the mountain of Vaals, berg=mountain, Vaals is a dutch village") we share with two other countries - Germany and Belgium.

Recoil is certainly an issue because it determines with how much force and how long the rifle interacts with the body during the shot. With F-TR however there is not much choice in calibers.

The reason I won that f-class match in the Netherlands was, apart for the rifle,  because I was quite able in attaining the proper "zero position" and a consistent butt plate contact and head pressure, as well as the same (firm) grip.The result of small bore rifle shooting.   And, because of the ballistic calculations I knew wat max wind deflection would be.

More than a MoA penalty will be the result of not taking care of these things.