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Understanding the graphs

The graphs appearing in these web pages are rather complex and need some preliminary explanation.

The horizontal axis (labelled SPBB) is the number of shots per bagged bird. This is determined by shooter skill. In particular, SPBB is a function of the average aim error of the shooter.

The vertical axis (labelled "W per 100") is the number of birds wounded per 100 birds bagged. Some birds will be seriously injured and others will receive only minor injuries --- we make no attempt to categorise woundings in any way. To be perfectly accurate we actually measure woundings per 100 bagged. There is a subtle difference which I call the Gauntlet Effect .

In each graph we present figures for 4 different chokes: 60%, 70%, 80% and 90%. These are labelled with 0.60, 0.70, 0.80, and 0.90 respectively. By definition a 70% choke is what shooters normally call "full choke". But a gun that shoots a 70% pattern with lead will usually shoot a higher density pattern with steel. We include the 90% line to roughly simulate situations where the shooter is much closer than 40 yards and the pellet cluster hasn't spread too much. Such a high choke is useful to estimate the lowest possible range of wounding rates.

In all cases the graphs represent the results of firing at most 2 shots with the second shot being taken whenever the bird isn't bagged on the first shot.

Each graph has a line of numbers which characterise the major parameters used to generate it. For example:

P=141 5(1,2)2 218.00 68.00

P=141 gives the number of pellets, next comes the bagging criteria --- 4 numbers p(q,r)s which specify the number of pellet hits required to bag the duck. Lastly come the the total and vital areas of the duck in square cm.

The lines labelled 60, 70, ..., 100 represent average aim error in cm. In the figure below, for example, a person using an 90% choke and bagging a bird every 8 shots has an average aim error of about 80cm. If that same person moves to an 80% choke gun, their SPBB rate will drop, but their wounding rate will increase.