Editing the Current Data for the Gun

The effect of gun barrel length is accounted for in the measured velocity, so the only attribute due to the gun is the degree of choke, this being the degree of constriction at the muzzle.

The program conveniently uses the traditional measures of choke, i.e.:

For the purposes of this program it is strongly recommended that, wherever possible, you use the measured choke of your gun (based on pattern-plate firings repeated several times using your intended cartridges drawn from the same batch) rather than the nominal choke as marked on the gun - because this can vary, especially when using different shot materials.

Now, to change the nominal choke, at Current Data panel, move the bright blue highlight down to the line for Choke, and press the & (sideways arrow) keys to select the required degree of choke. If your combination of gun and new ammunition type has a measured pattern of 78% then this does not conform to the nominal chokes, so press the arrow until "Other" is displayed, and then press the PageUp or PageDown keys to change the percentage. This section of the panel will then appear so:

For the purposes of this worked example, you could see what effect changing the nominal choke to 'improved cylinder' has on the performance. Use the & arrows to select, and press G (Graph) to see the result. Then try changing to 'full choke' too and see the effect on performance.

When done, return the choke to 'half' to continue with the worked example.