p. 155 Three-Dimensional Representation
The general shape of the shot cloud revealed that the pellets arriving first (leading edge) are located in the centre of the pattern, and the trailing edge pellets appear at the outer regions. The deformed pellets, collected at the outer parts of the pattern, travel at the trailing edge shot cloud. The well formed pellets, associated with the pattern centre, are to be found at the leading edge of the shot cloud. With the greater associated deformation on pellets at the rear of the load, caused by the pressure in the barrel compressing them into the pellets above, a similar relationship between the pellets deformation and location in the shot cloud is seen in both experiments.
SUMMARY
p. 160 The longitudinal distribution of pellets in the shot cloud at ranges between 20-50m was shown, via shot cloud length, to be unaffected when the internal ballistics of the gun, such as choke, were altered. However, from high speed photography it is known that the initial distribution of pellets is affected by the internal ballistics. Therefore it is assumed that the in-flight effects of the pellet become the more dominant factor, thus masking the internal ballistics effect, at ranges greater than 20m.
From the analysis of the shot cloud profiles it was established that the longitudinal pellet distribution is best described as a Rayleigh distribution.
Analysing the lateral distribution of pellets in the shot cloud it was established that there are two independent distributions, that is the horizontal (x) and vertical (y) pellet distributions. These two distributions were shown to be best described as Gaussian (bell curve) distributions.
Lateral pellet distribution did not reduce, after 0.030". These results were obtained using a linear tapered choke profile and further experiments are required on different choke profiles to verify this relationship between lateral distribution and choke constriction.
It has emerged clearly from this work that it is not possible to produce a satisfactory theory which can predict the downrange behaviour of shot clouds from the muzzle condition in sufficient detail. Further work is required to understand the full effects of choke constriction and choke profile on shot clouds.
It was shown that the launch effects were the major influence on the shot cloud width and the in-flight effects were more dominant in the shot cloud length masking the possible launch effects over the measurement ranges.
