Round MilDot metric – analogue mil-ranging solver

Round MilDot is a logarithmic slide rule bent into a circle: two discs and a rivet. Set the target size in centimetres against your reading in mils and the window shows the range in metres, from 100 to 1200 m.

The formula is printed on the disc — range (m) = target (cm) × 10 ÷ mils — so any result can be checked by hand. What the disc takes away is the division and the decimal point, and behind a rifle, under stress, that is where the mistakes come from.

• Target scale 10–100 cm against the MIL ring 0.1–10
• Range 100–1200 m in the window, logarithmic scale
• Slope arrows 15–60° with cosine: the horizontal range straight away
• Spotter tables: wind from flag and mirage, target speed, angle factor for wind and movers
• Dimensions on the back: range targets, or vehicles and road signs — two versions

• Mid-range and PRS shooter — range without a laser, on stages that ask for it.
• Spotter in a pair — wind from flag and mirage, target speed and angle factor in one hand.
• Hunter — distance when the laser gets no return from game in grass or fog.
• Training — it teaches the cm × 10 ÷ mils relationship a shooter has to understand anyway.

Who it is NOT for: the disc computes neither elevation nor wind holds in mils — that is your DOPE card or solver. A second focal plane (SFP) reticle reads correctly only at its calibration magnification.

Every electronic device is a battery, an emitter and a single point of failure. A serious ranging plan has layers, and the layers that still work when everything else is off are analogue.

• Jamming is routine now — Satellite-navigation interference has been reported around the Baltic Sea since 2023. Anything that depends on GNSS or a radio link can be denied. A disc cannot.
• Every emission is a signature — Laser rangefinders and IR illuminators can be picked up by warning receivers and night-vision devices. Looking through a reticle emits nothing.
• Skills decay silently — If the laser does all your ranging, the day it fails you range by guesswork. A few minutes a week with the disc keeps the relationship in your hands.
• Issue one to everyone — No charging, no batteries, no updates. A disc costs a fraction of a rangefinder and can go to every member of a team, a club or a civil-defence unit.

Steel plates 12 and 20 inches wide are the standard long-range targets. On the metric disc they are 30.5 and 50.8 cm. Learn the ladder: your partner calls a reading, you set the disc and call the range, then check it against the table.

Set on the disc: 30.5 cm is half-way between 30 and 31; 50.8 cm just above 50. Values above 1200 m are beyond the disc's range scale: for the 20″ plate at 0.4 and 0.3 mils use the formula.

• ✓ Lower disc: Ø 116 mm — production die
• ✓ Upper disc: Ø 100 mm, window wing to Ø 116 mm — production die
• ✓ Centre hole Ø 4.51 mm, screw rivet — production die, coaxiality < 0.01 µm
• ✓ Scales: target 10–100 cm, MIL 0.1–10, range 100–1200 m — production files
• ✓ Scale reading error ≤ 0.23 % — scale audit on the production files
• ✓ Slope arrows 15–60° — deviation from the cosine at most 0.04°

• 1 · Measure — read how many mils the target covers in the reticle (FFP: any magnification; SFP: the calibration magnification).
• 2 · Set — turn the discs until the target size in cm sits against your reading on the MIL ring.
• 3 · Read — the range in the window at the 0° index, or the horizontal range at the arrow for your slope angle.

Examples: an IPSC target 45 cm at 0.9 mils → 500 m · a torso 50 cm at 2 mils → 250 m · a 240 l wheelie bin (110 cm, half of it 55 cm) at 1.1 mils → 500 m.

• Black — white print on black matte polymer.
• White — black print on white.
• Range back — IPSC and IDPA targets, poppers, E and F type silhouettes, in cm.
• Field back — vehicles, a crouching figure with a dog, weapon lengths, road sign dimensions and a grid for notes.