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#1




Ftlb constant for muzzle energy
What is the muzzle energy constant used in disciplines for calculation of muzzle energy?
Reason for asking, I've come across a few different constants used in various online energy calculators. 8.4gn at 800 fps in one gives 12.00, another gives 11.90, another 11.93, another 11.94 It seems the constant is a 'fudge' to impart the acceleration due to gravity to work with weights, because imperial units use weight instead of mass... which varies across the globe, and seems to be rounded here and there. I'm 1/2 tempted to calculate using Joules and then convert back. Just trying to make up some easy reference to competition limits based on pellet weight.
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#2




I tend to use 32.174 for gravity, which would mean using 450436 in the calculation giving the answer
800 fps with an 8.4 grain pellet = 11.935 fpe (11.99fpe for an 8.44 grain pellet though) 
#3




Kinetic energy = 1/2 * mass * v^^2
Joules = 0.5 * Kg * M/s * M/s Ftlb ain't exactly SI :) It really is about time that FT went metric and then we would use real MOA not "Shooters' MOA" 800fps = 243.84 M/s 7.9grains = 0.51191g = .00051191Kg Energy = 15.2J 11.22ftlb If it was 8.4grains then 16.18J for "800fps" Velocity squared really makes the difference when it comes to errors or hammer settings. Grain of what? wheat? rice? presumably it was some cereal crop :)
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#4




Quote:
If in Edinburgh then 32.204 So 32.174 puts you somewhere in Spain as a rough guess. Think we need to bin the imperial units
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#5




Too technical for me I just work on the fact if it's 8.4 and doing 800 turn it down a little

#6




Quote:
If only there was an international standard for this for of thing 
#7




I *think* Chairgun uses 32.174
I use 32.194 for my wind calculation game  which might be slightly wrong for Spain or Scotland 
#8




My scales weighed less in SA...
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#9




Why are you concerned about Gravity? You only measure mass and velocity. No force needed and no measure of acceleration or deceleration.
Pellet drops in flight of course. Actually nobody weighs pellets accurately anyway. If it becomes an issue you need a set of BFTA weights equivalent to, say, 10 7.9s or 8.4s. Then you make a reasonable average for 10 over any slight variation between pellets. Balance scales are always better than anything based on a load cell ( strain gauge ) but it is highly unlikely that a course would ever be up to a laboratory standard.
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BFTA Secretary 20122014 CSFTA Secretary 20142016 Last edited by neilL; 11th November 2014 at 12:25 PM. Reason: Mass vs Weight 
#10




Although we only measure mass and velocity  we need to express the answer as a force in fpe (to comply with the law). That's where gravity comes along and screws things up

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