FREE Ballistics Calculators And Data Charts from Canada's NFA
Ever wondered what twist rate is required to stabilize a particular bullet? Or would you like to see how changes in spin rates (rpm) affect bullet stability? Well thanks to our friends from Canada, you’ll find helpful formulas online that answer many questions about external ballistics.
The Ballistics Page for the Canadian National Firearms Association (NFA) website offers a variety of useful programs and data charts created by Peter Cronhelm. These include:
Greenhill Formula Twist Calculator
Bullet Stability Calculator (requires MS Excel)
Ballistic Coefficients Chart (MS Word), (Or DOWNLOAD HERE.)
Ranging Ballistics Computer (Scroll to bottom of page.)
This exterior ballistics computer works in conjunction with range data as well as computing a conventional drop and windage chart. Using an FFP (Final Firing Point) and multiple TRP’s (Target Reference Points) the system will simultaneously calculate Drop and Windage data for up to 30 TRP’s 360 degrees around the FFP. Windage is corrected for the TRP direction compared to the primary wind direction. The spreadsheet consists of six individual pages. Each page performs a distinct function and contains all the information required to complete a shot at a target or targets. The entire system can be used in any laptop or handheld computer capable of running MS Excel or Excel CE.
CLICK HERE to download Ranging Ballistics Computer (requires MS Excel)
Rimfire Ammo Comparison Table
Canada’s NFA even provides a detailed table with bullet weights and velocities for over 100 varieties of 22LR Rimfire ammunition from Aguila, CCI, Eley, Federal, Fiocchi, Lapua, PMC, Remington, RWS, and Winchester. This Rimfire Ammo Table is a “must-have” resource for any smallbore shooter. Shown below is the section for Lapua:
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Robert Whitley wrote:
“While I applaud the efforts of Canada’s NFA to put out these sources, I think Peter Chronhelm needs to tweak things a little, especially on the bullet stability calculator (excel). If you plug in a bullet like a 6mm Berger 105 VLD bullet going 2800 fps, the calculator says the stability factor is not nearly adequate with a 1:8″ twist barrel, meaning the bullet would not even be stable shooting it out of a 1:8″ twist barrel. This also is the case with a 115 gr 6mm out of a 7.5″ twist barrel, but anyone who shoots 6mm’s knows that a 1:8″ twist will fully and adequately stabilize a 105-108 gr 6mm bullet and the 115’s are all well stabilized by a 7.5″ twist barrel.
I don’t want to “pour cold water” on what Peter has done, but it’s no good to put something out there that does not give accurate information and results and winds up misleading people.
Maybe I just don’t know how to use the calculator, but I am pretty sure I was using it correctly.”
Robert Whitley
EDITOR: Robert Whitley makes some very good point. Testing his example, we ran the Berger 105s through the calculator at 2800 fps and came up with a stability factor of 1.0, listed as marginally stable. The recommended stability factor is 1.3 or greater. It could be the model doesn’t work particularly well with VLD-style bullets which tend to be longer for their weight. Bullet length is one of the key variables in that Excel calculation.