Not everybody has the (safe) room to shoot at airgun targets at the regulation distances. Nice as it is to take shots at a full sized target at reduced distances it's not quite the same as being able to say how well you are doing in comparison to people shooting the real distances.
The way to deal with this is to use Ian Pellant's rather wonderful software to print targets the right size for your personal range, but not any easier to hit than the full sized one at the right distance.
Bear with me while we work through how to do this...
Consider the 10 ring of a 10 metre Air Pistol target, at 10 metres it's 11.5 mm across. You score a 10 if you cut the line, so it's actually 11.5 + (half the width of a pellet on either side) mm. Given that 0.177" (4.5mm) is the standard for target pellets that measn that a pellet with it's centre up to 8mm from the true centre of the target will score a 10. (the 10 scoring zone is 11.5 + 2*(4.5/2)mm across)
If we scale the scoring zone instead of the ring sizes then we can deal with the problem that the pellets dont get smaller as the range increases.
Multiplying the scoring zone by the proportion of the range that we want to shoot at gives us the size of the scoring zone that we want. Time for an example... let's say that we want to shoot a 10m air pistol target on an indoor range that is only 5.5m long:
The ring is 11.5mm & the scoring zone is therfore 16mm. We're shooting at 5.5 / 10 of the official distance, so the scoring zone will be 16 * (5.5/10) mm or 8.8mm across
Good, but we forgot to allow for the pellet size, which we added initially. So remove the 4.5mm that accounts for the 10 scores when the pellet centre is not actually in the 10 ring & we get 4.3 mm! I know, you were hoping for more. Me too.
If you've managed to get over the shock I'll let you have the formula:
New Ring size = ((old ring size + pellet size {mm}) * (new distance / Standard distance)) - pellet size {mm}
It has been pointd out to me that the size of the aiming spot does not shrink at the same rate that the scoring rings do. You'll need to add another ring to the outside of the scoring zone, coloured black & with a size = (size of 7 ring on full sized target) * (new distance / standard distance)
This is not the full size of the 6 ring, but does give the target the same visual size to aim at. If you shoot badly enough to need it you'll discover that with the airgun target software you've sacrificed the 1 ring in order to split the 6 into a black & a white half.