Reticle ranging is a division problem: a target of known height subtends a measurable angle, and the angle tells you the distance. The maths is trivial. The measurement is not, and the measurement is what this drill trains.
The arithmetic, once
With a MIL reticle, distance in metres equals target height in millimetres divided by the measured mils. A 1,800 mm human standing 3.0 mils tall is at 600 m. That is the whole formula, and it works because a mil subtends one thousandth of the distance.
With MOA it is less tidy: distance in yards equals target height in inches multiplied by 95.5, divided by the measured MOA. Workable, but not head arithmetic under pressure — which is one of the practical arguments for MIL.
Why small measurement errors hurt
| True size subtends | You read | Error | Ranged distance for a 1,800 mm target |
|---|---|---|---|
| 3.0 mil | 3.0 mil | 0 % | 600 m |
| 3.0 mil | 2.9 mil | 3 % | 621 m |
| 3.0 mil | 2.8 mil | 7 % | 643 m |
| 3.0 mil | 2.5 mil | 17 % | 720 m |
| 1.5 mil | 1.4 mil | 7 % | 1,286 m instead of 1,200 m |
Two things follow. Distance error scales inversely with the measurement, so a tenth of a mil matters more the smaller the target appears. And ranging small or distant targets is inherently imprecise — at 1,000 m a torso subtends well under a mil, and reading it to a tenth is optimistic.
Setup
| Item | Detail |
|---|---|
| Targets | Three to five, of known dimension, at unmarked distances between 300 and 800 m |
| Reference | A laser rangefinder — for scoring only, not during the drill |
| Rounds | One per target, per pass |
| Support | Bipod and rear bag. Milling from an unstable position is a separate, harder drill |
| Recording | Measured mils, computed distance, true distance, impact |
The drill
- Pick a target and identify its known dimensionA steel plate's height, a fence post, an IPSC target's 450 mm width. Write down which dimension you are using.
- Measure it in the reticle to the nearest tenthTake your time on the first passes. Bracket the target between two stadia and read carefully.
- Compute the distance and write it downBefore you look at anything else. This is your prediction and it is what gets scored.
- Solve and fire one roundEnter your ranged distance, take the elevation, hold for wind, shoot.
- Laser the target and record the truthNow — not before. Note the percentage error in your range and where the round landed.
- Repeat across all targets, then twice moreThree passes over five targets gives fifteen data points, which is enough to see a pattern.
Scoring it
| Range error | Verdict |
|---|---|
| Under 3 % | Excellent. Good enough to hit with inside 700 m |
| 3–5 % | Workable. Expect misses on small targets at distance |
| 5–10 % | Needs work. Usually a reading problem, not a maths problem |
| Over 10 % | Check your assumed target dimension first |
Look for bias as well as size. Consistently ranging long means you are reading the subtension small — often by measuring to the visible edge of a target rather than its true extent, or by bracketing generously.
Pass mark
Five consecutive targets ranged within 5 per cent, with first-round hits on at least three of them. That is a realistic standard for a supported position at practical distances.
Making it harder
- Time limit. Sixty seconds from target call to shot, including the milling.
- Unsupported positions. Reticle wobble is the dominant error source from kneeling or a barricade.
- Partially obscured targets. Range from a visible portion of known size rather than the whole.
- Low light. The end of legal shooting light is exactly when the laser is least reliable and the shot most likely.
Common mistakes
- Assuming a target dimension. 'Deer are about a metre at the shoulder' has ended more shots than bad wind calls.
- Reading at the wrong magnification. A second-focal-plane reticle is only calibrated at one magnification. Know which.
- Rounding to the nearest half mil. At 800 m that rounding is a hundred metres.
- Skipping the shot. Ranging without firing removes the consequence, and the consequence is what makes the lesson stick.
The app's ranging tool does the arithmetic from a measured subtension and a target size, with presets for common references, and hands the result straight to the solver. The screen-by-screen version is in ranging with your reticle.
Frequently asked
Is reticle ranging still worth learning with a laser in my pocket? +
Yes. Lasers fail on rain, snow, brush, dark hair and low-reflectivity surfaces, and batteries die in the cold. Reticle ranging is the fallback that works when the electronics do not.
Does it work with a second focal plane scope? +
Only at the magnification the reticle is calibrated for — usually maximum. At any other setting the subtensions are wrong. First focal plane reticles are correct at every magnification.
What target dimension should I use for game animals? +
Use a dimension you can verify for the species and region you hunt, and treat it as an estimate with real uncertainty. Body sizes vary enough that ranging off them carries error a plate does not.