APPROACH

There are four main elements:

The analysis
Game presentation
The program
Program data;

these are discussed in turn.

The Analysis

First, the down-range ballistics of the pellets is calculated (Appendix D). It is assumed that velocity differences within the shot cloud will have a relatively small effect.

The lethal and incapacitating potential achievable against all the regions of the quarry anatomy have been assessed and then quantified in the supplied 'quarry datafiles' (Appendices F, G, H, I and J). The regions specified in these datafiles are categorised according to similar susceptibility to impact. Each region has an assigned presented area, forming a column of tissue which has layers within which there are common properties in terms of thickness, penetration resistance, and response upon injury. Only short timescale responses to injury are assessed as only these have any bearing on the 'bagging' of game in the context of game shooting, and these are reduced to the five broad categories of lethal, disabling flight, affecting running/swimming, concussion, and non-rapid effect. The potential injury to each region reduces with increasing range owing to the fall in impact velocity, so the total presented area for each category of potential injury reduces with range.

The discrepancy of aim is modelled by simulation using four rationally independent human factors relating to gun usage (Appendix B). This requires Monte Carlo type integration, and as such is comparable with practical in-the-field assessment of ammunition, i.e. requiring many thousands of rounds to produce a confident average.

In accord with UCL studies [Ref. Giblin & Compton] the pellet dispersion is taken to be Gaussian and to increase with time of flight (Appendix C). This enables the number-density of pellets to be found at the quarry location, and this is taken to be uniform over the quarry silhouette.

The probability of hit against each region of categorised potential injury is calculated, and on the basis of randomly distributed pellets, the probabilities of the various outcomes is predicted (Appendix K). The probability of retrieving downed birds depends on whether there is a retrieving dog to recover those birds which may run or swim. The average distribution of outcomes is found at each range, and this whole process is repeated for all ranges from the muzzle to 100m.

Of course the shooter will predominantly fire around specific ranges, so the results at each range are weighted according to a user supplied 'range policy'. Integration under the weighted probability curves gives the fraction of birds, relative to shots fired, in each category of outcome (Appendix L). These equate directly with the 'take-home-bag' and 'lost birds' referred to by shooters - hence the computed summary giving 'Bagged (per shot)' rate and 'Bagged per Hit' rate.

Orientation of the Quarry at the Moment of Firing

Observation of game shooting indicated that most wildfowling shots are taken at or near to the moment of closest approach. At that moment the quarry is usually already aware of the shooter's presence, so the bird has commenced evasive action, this being acceleration directly away from the shooter, whether the bird is low to one side of the shooter, or relatively overhead. In turning away, the bird presents an open-wing breast view, and the shooter usually fires at the then vulnerable quarry: the supplied 'quarry datafiles' assume this presentation of the bird. Follow-up second shots are expediently taken at fleeing birds which may have been hit, and the shooter has to be judicious in that a bird presenting a tail-end view can be difficult to 'bag' (see also Appendix F).

The Program

The program uses terms familiar to shooters wherever possible; new terms have been introduced only as necessary. The DOS environment maximises the accessibility of the program, though this puts some restraints on it's 'user friendliness'. The program User Manual comprises Part 1 which accompanies this document.

The Data

A basic data-set is supplied with the program (see list Appendix A, also Appendices E & J); this contains sufficient information for users to gain some insight into the potentials and limitations of alternative shot types. A list of the supplied datafiles is to be found in Appendix A. The program is designed to accept user-created datafiles and so is able to cope with other quarry species, shooter accuracies, ranging policies and, particularly, new alternative shot materials and cartridge loads.