However, this can be automatically converted to compatible units via the pull-down menu. Recoil Velocity (RV): The calculator returns the velocity in meters per second. INSTRUCTIONS: Choose units and enter the following: Ultimately then, it would seem prudent to use this value since I believe most clubs and polis forces use Skan chronos and using the larger constant will result in a lower value than using the higher one - so you could end up in a spot of bother if your gun is doing 11.99999ftlb calculated using the smaller constant.The Recoil velocity of a gun calculator computes the velocity at which a gun will move in the opposite direction in relation to the projectile that it fired. despite it not really being aligned with the "standard gravity" value. Repeating the calculations above for the new velocity gives an energy value of 11.7047ftlb for the constant 450240, and 11.6996ftlb for the constant 450436 so it appears that the Skan uses the more traditional value of 450240. I've just had a look at the Skan and the energy value reads to 3 decimal places so actually it should be possible to determine which constant (if either) it uses.Ī test shot with an 8.40gn pellet gave a velocity of 792.07ft/s and an energy of 11.704ftlb. Recalculating using the constant 450436 gives an energy value of 11.4917ftlb carrying through that 0.040% difference from the constant to the energy. Calculated using the smaller, traditional constant of 450240 gives an energy value of 11.4967ftlb. To illustrate the influence of using different conversion factors, let's say we have an 8.4gn pellet travelling at 785ft/s. which sounds about right as 8ft/s would obviously be 1/100th or 1%. Using this method applied to the 5ft/s within 800ft/s, I get: then minus the 5fps.Ĭlick to expand.For the conversion constant I arrived at the difference between 450236 as a percentage of the larger number in the following way: So we'll use 16.270 Joules, as at least the online calculators agree that's 12.0001 ft-lbs. So I was just trying to work out what figure to use for a set of pellet weights we could stick on the CSFTA chrono, so that when someone comes along with a 7.6gn pellet, we know what they should be flying at, and that figure isn't upset by Holly's wallet bending the earth's gravitation field or us being at one end of the region to the other, as gravity varies by latitude as well. I've got no idea what chronos use as a constant either, but the working practice is to just measure the velocity. Working with SI, we lose the weight calculation of the formula, and there's no constant to worry about. or in other words, 50% of what the BFTA for instance use as a the deciding limit. The margin of difference is about 2-3 fps between those constants. Not a massive difference granted, but if you're going to say just use one decimal place, then the rounding error could see you 11.9 or 12. some use 450450, some use 450236, some dont state it. it entirely depends on where you get your muzzle energy calculator formula from.
Often the "7000 (the amount of grains in a lb) by gravity x 2" bit is replaced by just a number say 450240. Muzzle Energy = weight x velocity squared / 7000 (the amount of grains in a lb) by gravity x 2
wieght = force = mass x acceleration (gravity) and that's where the gravity bit comes in.
But being english, we're still measuring using potatoes and weight, not mass with the old 12ft-lb formula. Click to expand.With SI units Neil, gravity is removed, because we deal with mass.
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