Thursday, 7 August 2008
Pulanamic Penetration Profiling
My new interest – like all my interests – is gathering pace rapidly. What I am particularly interested in is what I describe as the penetration profile. That is the variation of pellet penetration within the shot cloud and whether one could thus estimate the potential penetration profile for a given load.It has been demonstrated by Compton & Giblin3 that individual pellets within a shot cloud travel at varying velocity, and thus there will be a difference in the terminal velocity and energy of pellets within the shot cloud. Examples of differences in leading and trailing edge velocities and energy are shown in their report.Where Compton and Giblin illustrated a shot cloud profile as “a side-on view of the shot cloud in space”, I wanted to show a side-on view of the penetration of the shot cloud.They went on to say “The shot cloud profiles offer unprecedented detail in the quality control information that it can give, particularly with regard to the pellet energy variation within the shot cloud. They also made the point that their studies showed that there was no single value for the flight time of a given load to a particular range and that there can be significant differences between flight times of leading and trailing edge pellets in the shot cloud. Thus there can be no single velocity for a given range. They went on to show large calculated differences in the kinetic energy between leading and trailing edge pellets.In one example at 40 metres they calculated a difference of 20% in pellet kinetic energy between leading and trailing edge pellets. This possibly making part of the shot cloud ineffective.Unfortunately, the significance of shot cloud profiles and the variability of pellets within the shot cloud appears largely to have gone unnoticed by the great majority of shooters. Most shooters, probably unconsciously, assume that each and every pellet within the shot cloud has the same velocity and energy value at a given range. I know better. Ducks and geese beware.