Long Range Shooting Essentials
Basic Essentials Of Long Range Target Shooting - Part 3.
The Projectile Is The Key Component
In Part 2 we came to the conclusion that the most significant ballistic advantage is found by selecting the projectile with the highest BC. It requires searching the manufacturer's product listing for target projectiles that have high BC and that can be fired at velocities high enough to return optimum performance.
Its not always as simple as picking the bullet with the highest BC because some calibre and case combinations cannot combine to provide the same velocities. There will be instances when the high BC bullet of interest cannot reach the velocity of similar bullets that have only marginally lower BCs. Then we do a comparison of the projectiles that have similar BCs but differing velocities to determine which is deflected less by the wind. One combination will come out ahead of the others and this is probably the choice you want to use.
I use internet resources to determine what velocities are available from various calibre and case combinations and I suggest you do the same. I use the Calibre Info pages on 6mmbr.com to get some idea of what velocity is possible. Once you have the bullet selected and a realistic velocity, then it comes down to a simple comparison using Excel and BfX functions or using ballistic software to compare the numbers.
If the high BC bullet is the key component then all the hard work is wasted if its launched from a rifle with an insufficient turn ratio, (twist) in the barrel to stabilise it! The Gyroscopic stability factor (Sg) according to Bryan Litz should be around Sg = 1.4. When Sg = 1.0 a bullet is said to be stable but that is for a set of very specific conditions. Better to follow Bryan's advice and aim for a figure of approx Sg = 1.4. Don Miller published his formula for calculating the stability of spin stabilised bullets in 2005 and as a consequence significantly advanced the understanding of stability for use in exterior ballistics. The spreadsheet I put together with BfX functions now includes a stability calculator using Miller's formula.
We have found the perfect projectile and know what velocity needs to be used to optimise it, what could possibly go wrong? My 12 year old son has just started shooting in F-Standard and I know the 308W with the 155gr HBCs are the best ballistic combination but I've got him shooting a 223R. Simple matter of the recoil being minimal and allowing him to concentrate on his shooting skills without having to contend with bipod jump and potential flinching.
We now have left ballistics behind and are dealing with basic physics and physics tells us that if we want to reduce recoil we could reduce the powder charge and the weight of the bullet. These are the very things we want to leave alone so what else can we do? We make our rifles as heavy as is allowable under the rules to reduce the effects of recoil. Everyone can deal with different levels of recoil so if you are considering the optimal F-Open gun with heavy loads and projectiles, then try and shoot a members rifle of the same spec you want and discover if the recoil is acceptable.
BfX Functions For Excel
Most people can use Excel spreadsheet applications and those that cant can easily learn, just google how to use Excel spreadsheets and a wealth of info will appear.
To use the BfX functions you need to download the Excel Add-in file that Robert Meijer has written the code for and named BfX.xll. This file has to be loaded into the correct computer file location and Excel needs a link to know it has been installed. All very complicated but thankfully Robert has also made an installer program that loads it in automatically, just like any other application you might load into your PC.
Read the instructions given on the website and download the installer pack for your version of Excel. After you have run the installer program you need to then run Excel to tick the BfX box in the Excel Add-in Manager. All this info along with screen shots of how to do it are on the BfX website. If you have a problem then join the BfX forum and ask as many questions as needed to get it up and running.
My Spreadsheet Displayed My Way
- Displays 10 calibres and loads side by side or 10 variations of one load if thats whats wanted.
- Displays wind deflection.
- Displays bullet drop.
- Displays gyroscopic drift (spin drift).
- Velocity at 1000 yards.
- Recoil energy.
- Separate stability calculator.
- Seperate metric/imperial units calculator.
The spreadsheet fits on a single page and after you have finished using it to compare calibres and loads for your next project, it prints out on one sheet of paper in landscape mode. This way of evaluating data is simpler and much clearer than printing out 10 ballistic tables to view and consider.
The spreadsheet has now been upated and allows either metric or imperial units to be entered and are displayed in blue text. The spreadsheet has been tested using Excel 2007 but should also be compatible with Excel 2003.
2 Versions Available With The First Displayed Spreadsheet Being Compare Only!
The Second Spreadsheet Provides Range Charts And Compares 10 Loads!
End Of The Article
Its over to you now to use this information to get a better understanding of how ballistics can be used to give you an advantage. At the very least this knowledge will put you on a level playing field with those shooters already putting it into practice.
Download the Berger Bullets ballistic software its a great application and perfect for printing off drop charts. The spreadsheet is my preferred option to compare loads and calibres so also download the BfX Excel Add-in and the spreadsheet. The thing about Excel and BfX is that it enables you to display ballistic data how you want and that makes for a very powerful tool now sitting on your desktop.
Buy Bryan Litz's book "Applied Ballistics For Long Range Shooting".
Download Robert Meijer's brilliant BfX Excel Add-in. Download Add-in
Download the latest updated version of the spreadsheet here: BfX Ballistic Range Chart
Download spreadsheet here: BfX_CompareOnlyBallisticSpreadsheet
Download spreadsheet here: BfX RangeChartAndCompareBallisticSpreadsheet
BfX Functions Used In The Spreadsheet
BfX_Tx() for use in Litz's approximation formula for spin drift.
BfX_Vx() for velocity at 1000 yards.
BfX_Y() for wind deflection.
BfX_D() for bullet drop.
BfX_U() for conversion calculators.
Lots more of these functions are available and just waiting for me to try out!
Please let me know if you find any mistakes! Webmaster
Ian Pavy safclass.com.au