Learn › Track 02 · Equipment & physics
Sights, light gaps & clicks
Your sights are two pieces of metal 30 to 40 cm apart: a rear notch near your eye and a front blade near the muzzle. Tiny errors between them get blown up on the way to the target. How much?
Think first: Your front blade sits 0.1 mm off-centre in the rear notch. The sight radius is 350 mm. How far from your aim point does the shot land at 10 m?
That gap between angular error (sights misaligned) and parallel error (whole pistol shifted, sights still aligned) is the reason this lesson exists. Play with the numbers:
A misaligned picture costs about thirty times more than an aim that drifts with the sights still lined up. Good sights are the ones that let you judge alignment quickly and the same way every shot. The technique side is in sight alignment vs sight picture.
What the rules allow
Open sights only. Banned: fibre-optic, light-gathering or reflective coloured sights; optical, mirror, telescope, laser or dot sights; any device that fires the pistol or signals when to fire; protective covers on sights. The pistol must fit the measuring box with its sights fitted.
Think first: Which change keeps your pistol legal?
- A red fibre-optic insert in the front blade so it stands out
- A narrower front blade swapped in from the maker’s kit
- A small dot sight on a rail, used only for sighters
Sight radius
The sight radius is the distance between rear notch and front blade. On top pistols you can move the front sight to change it.
| Pistol | Adjustable sight radius |
| Feinwerkbau P8X | 330–400 mm |
| Morini CM 162EI | 310–350 mm |
| Pardini K12 | 340–385 mm |
| Steyr Evo 10 (Compact) | 316–365 mm (266–315 mm) |
| Walther LP500 | about 338–399 mm |
A longer radius makes every alignment error cheaper. At 330 mm, an error is magnified about 30 times; at 400 mm, 25 times. Move the slider in the calculator above to see it. The price is that the front blade sits further from your eye, so it looks narrower and the light gaps beside it look wider.
Blades, notches and light gaps
Front blades and rear notches come in different widths. Feinwerkbau, for example, offers front blades from 3.6 to 5.1 mm in 0.3 mm steps and rear notches from 2.0 to 8.5 mm wide. Steyr's rear notch runs from 2 to 6 mm wide and 1 to 3 mm deep.
Together they set the light gaps: the strips of light you see either side of the blade. Alignment means the top of the blade is level with the top of the notch, with equal light on both sides. Compare three set-ups:
Think first: In the left picture the gaps are thin slivers of light. What goes wrong as the pistol wobbles?
- Nothing: thin gaps are the most precise
- The slivers close and open, so you lose the reference you need to centre the blade
- The target becomes blurrier
Gap : blade : gap of about 1 : 2 : 1 is a common starting point, not a rule. Older eyes usually want wider gaps. Change blade width, notch width or sight radius one at a time, and judge it over a full session.
Try lining up the blade yourself:
Clicks and calibration
The rear sight moves in clicks. Makers quote a click value: on the Pardini K12, one click moves the shot 1.8 mm at 10 m.
Click values found for other pistols are unconfirmed (one source gives 0.8 mm per windage click on the Walther LP500). Treat any published value as a starting point and measure your own.
To measure your own click value:
- Shoot a group with your normal hold and routine.
- Move the rear sight 10 clicks in one direction, for example up.
- Shoot a second group the same way.
- Measure the distance between the two group centres and divide by 10. That is your click value.
Moving the rear sight follows one simple rule: move it the way you want the group to go.
Think first: The centre of your 10-shot group is 9 mm left of the middle. One windage click moves the shot 1.8 mm. How many clicks to the right?
Practise the corrections in the sight adjustment simulator, and see groups, MPI & sight adjustment for reading the group itself.
- Angular (alignment) error is magnified about 10,000 ÷ sight radius at 10 m; parallel error only 1 : 1.
- Open sights only: no fibre optics, optics, dots, lasers, signals or sight covers.
- Longer sight radius makes alignment errors cheaper but makes the blade look narrower.
- Light gaps must stay visible and equal through the wobble. 1 : 2 : 1 is a starting point.
- Measure your click value with a 10-click move, and move the rear sight the way you want the group to go.