Strichplatte / graduated range plate (MG mount); reticle (Optics).
TM 30-506, WAR DEPARTMENT TECHNICAL MANUAL, GERMAN-ENGLISH MILITARY DICTIONARY, WAR DEPARTMENT, 20 MAY I944
A Strichplatte (Reticle) range finding scale, measured in mils, with vertical lines extending from 0 in the center to 40 mils to the right and left in increments of 10 mils, was built into the right lens of many German military and naval binoculars.
Dienstgläser with the Strichplatte range finding scale were marked in weißer Schrift (white letters) on the right prism cover with “m” or “M” (indicating mils) followed by “H/6400” (indicating that the range finding scale is divided into 6400 segments measured in mils).
Between 1938 and 1939, the “m” or “M” was discontinued, and only the “H/6400” was retained to show that a Strichplatte (Reticle) range finding scale was built into a particular Dienstglas.
The “m” or “M” preceding “H/6400” is often confused with the capital letter “M” marked beneath or near the Reichsadler symbol that identifies property of the Marine (Navy).
There are two main types of reticles:
Wire reticles
Etched reticles
Wire reticles are the oldest type, and are made of metal wire or thread mounted in the Dienstglas right lens.
Etched reticles are imprinted on the lens as an integrated part of the optics mounted within the right tube.
When backlit through the right ocular (light gathering front objective), a wire reticle will reflect the incoming light and not be seen as a black image with high contrast. When backlit, an etched reticle will be seen as fully black.
Etched reticles are more refined, and offer greater reticle layout flexibility. In more complex binoculars (more expensive to manufacture), etched reticles dominate. In less complex binoculars (less expensive to manufacture), wire reticles are preferred to avoid a rather specialized and costly production step.
Strichplatte vertical ranging scale
The four horizontal lines rising vertically over the main horizontal line of the Strichplatte rangefinding reticle was used by small group leaders, artillery forward observers, and sniper team spotters for quick, rough ranging purposes.
If the helmeted head of a man (≈ 0.25 m tall) fit between the fourth bar and the horizontal line, the man is at approximately 100 meters distance. If the upper part of the body of a man (≈ 1 m tall) fit under the fourth bar, the target stands at approximately 400 meters distance.
Dienstgläser with the Strichplatte (Reticle) in the right lens are designed for (stadiametric) rangefinding purposes, and are etched with small lines at milliradian (Mil or 1/1000 of a radian) intervals in the field of view. Training and practice enabled the user to measure the range to objects of known size, the size of objects at known distances, and compensate for both bullet drop and wind drift at known ranges with reasonable accuracy. To promote ease of use with mental calculations and communication between artillery spotters and gun batteries, the elevation or vertical adjustment and windage controls of reticle equipped Dienstgläser are roughly adjustable in 10 milliradian increments.
By means of a mathematical formula — (width or height of the target / number of mils) x 1000 = distance — the user could measure the range to a target. An object 1 meter tall or wide is exactly 1 mil tall or wide at 1000 meters distance. For example, if the user sees an object of 1.8 meters tall, the object is 600 meters distance — (1.8 / 3) x 1000 = 600.
German experience in severe, bitterly cold Russian winters highlighted some major problems in the use of Dienstgläser manufactured before the implementation of the cold resistant grease marked with a hellblaue Dreieck (light blue triangle “Δ”) in 1943. Harsh, bitterly cold winters in Russia caused problems for service glasses that resulted in serious experimentation to find suitable cold resistant greases to allow them to work properly. German snipers often used iron sights heavily because telescopic sights did not function properly in very cold Russian winters.
Adjusting artillery fire uses angular measurement (mils) to calculate the azimuth (bearing) and barrel elevation between the guns and their targets many kilometres away. Artillery spotters typically use binoculars calibrated in mils to walk fire onto a target, estimating the approximate range to the target and calling out the angle adjustments in metres for left / right and up/ down corrections.
The metre (British spelling) or meter (American spelling) (from the Greek noun μέτρον, “measure”) is the base unit of length in the International System of Units (SI). The SI unit symbol is m.
Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States, Sweden, and the Philippines, which use meter.
The roots of the term metre are traced to the Greek verb μετρέω (metreo) (to measure, count or compare) and noun μέτρον (metron) (a measure), used for physical measurement, resulting in the Latin (metior, mensura), and French (mètre, mesure).
As a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. That commission advised the adoption of the decimal system, and created the term mètre (“measure”) as the basic unit of length. In 1793, the French National Convention adopted the decimal system, and by 1797, the decimal system began to be used in England and other countries.
1 metre is nearly equivalent to 3 feet 3 3⁄8 inches.
A milliradian, often called a mil or mrad, is a derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). Mils are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel (up, down, left or right). Mils are also used to compare the difficulty of hitting different sized targets at different distances. Using Dienstgläser with mil markings in the reticle, soldiers can estimate the range of a known size target, or determine a target size if the distance is known.
Dienstgläser with Strichplatte (Reticle) are graduated into 6400 mils, which today is still the standard of measurement for optical equipment in the NATO countries.
Around the start of World War I, France was experimenting with the use of milliemes (6400 in a circle) instead of decigrades (4000 in a circle) for use with artillery sights. The United Kingdom was also testing them to replace degrees and minutes. Milliemes were adopted by France, although decigrades also remained in use throughout World War I. Other nations also used decigrades. The United States, which copied many French artillery practices, adopted mils (6400 in a circle). Before 2007 the Swedish defence forces used “streck” (6300 in a circle, streck meaning lines or marks) (together with degrees for some navigation) which is closer to the milliradian but later changed to NATO mils. After the Bolshevik Revolution and the adoption of the metric system of measurement (Russian artillery replaced “units of base” with meters) the Red Army expanded the 600 unit circle into a 6000 mil one. Hence the Russian mil has a somewhat different origin than those derived from French artillery practices.
In the 1950s, NATO adopted metric units of measurement for land and general use. Mils, meters, and kilograms became standard, although degrees remained in use for naval and aviation purposes, reflecting civil practices.
Rifle scopes and binoculars with mil markings in the reticle, can be used to measure how many mils to correct a shot even without knowing the shooting distance.
Range estimation with mil reticles
Many telescopic sights used on rifles have reticles marked in mils to serve two purposes, range estimation and trajectory correction.
Using a Dienstglas with a mil reticle, a soldier can estimate the distance to an object with a fair degree of accuracy by determining how many angular mils an object of known size subtends. Once the distance is known, the drop of a bullet at that range, converted back into angular mils, can be used to adjust the aiming point. A Dienstglas is marked with both horizontal lines used for range estimation, and vertical lines for bullet drop compensation. Experienced users can also use the horizontal lines to compensate for bullet drift due to wind. Dienstgläser with Strichplatte are well suited for long shots under uncertain conditions, such as those encountered combat by snipers and forward artillery observers. Soldiers must be able to estimate the range to targets at unknown (sometimes long) distances, so accurate compensation for bullet drop is required.
Estimating range using hands
Angle can be used for calculating target size or range, if one of the variables is known. Where the range is known, the angle will give the size, where the size is known the angle will give the range. When out in the field, angle can be measured approximately by using calibrated optics or roughly by using one’s fingers and hands. With an outstretched arm one finger is approximately 30 mils wide, a fist 150 mils, and a spread hand 300 mils.
Practical examples
A small vehicle, such as a Russian GAZ-67B (the Soviet equivalent of the American Willys Jeep), was known to be about 3.5 meters in length. If the target Russian GAZ-67B were seen from the side, a soldier holding up one finger in front of him could roughly estimate the target’s distance in front of him at about 100 meters.
, a “medium tank” (such as a Russian T-34 or American M4 Sherman) was about 6.5 meters in length. From the side, a Russian GAZ-67B or American Jeep was one finger wide at about 100 meters, and an average medium tank was one finger wide at slightly over 300 meters.
From the front or rear, a small vehicle was about 1.5 meters in width, and most medium tanks were about 3 meters in width.
If a Russian T-34 tank (about 2.5 meters in height, 2500 mm) is measured to 2.8 mils in the Strichplatte (Rreticle), the range to the target could be estimated to:
distance in meters = 2500 mm = 892.9 meters
2.8 mils
So if the above mentioned 6.5 meter long BMP (6000 mm) is viewed at 6 mils its distance is 1000 m, and if the angle of view is twice as large (12 mils) the distance is half as much, 500 m.
For maps and artillery, three rounded estimations are used which are close enough to the actual definition, but more easily can be divided into parts. The different map and artillery definitions are:
- 1/6400 of a circle in NATO countries.
- 1/6000 of a circle in the former Soviet Union and Finland (Finland phasing out the standard in favour of the NATO standard).
- 1/6300 of a circle in Sweden. The Swedish term for this is streck, literally “line”. Sweden (and Finland) have not been part of NATO nor the Warsaw Pact. Note however that Sweden has changed its map grid systems and angular measurement to those used by NATO, so the “streck” measurement is obsolete.
Reticles in some artillery sights are calibrated to the relevant artillery specification for that military, for example, the Carl Zeiss OEM-2 artillery sight made in DDR from 1969 to 1976 is calibrated for the eastern block 6000 mil circle.
Use in artillery sights
Artillery uses angular measurement in gun laying, the azimuth between the gun and its target many kilometres away and the elevation angle of the barrel. This means that artillery uses mils to graduate indirect fire azimuth sights (called dial sights or panoramic telescopes), their associated instruments (directors or aiming circles), their elevation sights (clinometers or quadrants), together with their manual plotting devices, firing tables and fire control computers.
Artillery spotters typically use calibrated binoculars to walk fire onto a target. By training and experience, they know the approximate range to the target, and so can call in the angle to give the left/right corrections in metres.
(Values in bold face are exact.)
- 1 trigonometric milliradian (mil) ≈ 3.43774677078493′
- 1 NATO mil = 3.375′ exactly
- 1 Warsaw Pact mil = 3.6′ exactly