DIFFERENT CALIBRE, DIFFERENT FLIGHTPATH
Four airgun calibres have established themselves for use in non-FAC, UK legal-limit air rifles: .177, .20, .22 and .25. When taking a typical pellet of a typical weight from each of these calibres, they will all trace very different flightpaths.
Muzzle energy is not the same as velocity – it’s a function of both pellet weight and speed, so a lighter pellet can travel faster than a heavier pellet, while having the same muzzle energy. In the case of a fast-flying .177 pellet, that speed translates to a flatter trajectory, as gravity has less time to affect the pellet, meaning there is less of a need to compensate for ballistic drop-off than with the .177’s larger, heavier and slower rivals. some very specific data, however, such as muzzle velocity, the weight of the pellet, its ballistic coefficient (this can usually be found online), the distance at which the rifle’s been zeroed and your sight height – the height of the centreline of the scope relative to the centreline of the bore.
Getting good results from a ballistics program relies on inputting peerless data, so you’ll need to use a chronograph to find the figures you need. It’s also important to verify your findings by shooting your rifle and correlating those results to your reticle. In many ways it’s simpler and more time-efficient to just get out there and shoot, carefully recording your results as you go. So that’s what we’ll do here.
WHAT’S THE AIM?
If you’ve never carried out this process before, it’s
