WEAPON ANALYSIS - OPTIMAL CALIBRE OF WEAPONS FOR MAXIMUM LETHALITY

Historical analysis of war and combat is an important field. One of the important contributors in historical study of war is T.N. Dupuy. His 1979 book Numbers, prediction, and war: Using history to evaluate combat factors and predict the outcome of battles defining a model of analysing combat between two forces has been in use in multiple contexts. It is called Quantified Judgement Method of Analysis (QJMA).

Weapon Scoring

The QJMA model assigns a basic score to each weapon in use. A score that is computed based on the calibre of the weapon. Calibre of a weapon indicates the diameter of the bullet/shell/bomb it fires, usually measured in millimeters (mm). For example, 7.62mm gun, 105mm Field Gun, 81mm mortar, etc. In Dupuy's QJMA, the score is called - Theoretical Lethality Index (TLI). The TLI when normalized with the dispersion factor of enemy troops is called Operational Lethality Index (OLI).

Operational Lethality Index - Potential Targets per Strike (PTS) and Rate of Fire (ROF)

The OLI of any weapon depends upon

potentially how many targets it can destroy per strike -Dupuy calls this factor the PTS,

the rate of fire (ROF) of the weapon - how many rounds of weapon can be fired in one hour,

range,

accuracy, and

reliability of the weapon.

For PTS and ROF, Dupuy has drawn curves for different calibres of the weapon. These are not linear curves.

Dupuy's PTS vs Calibre curve is shown below as Graph 1

The Calibre Vs Rate of Fire curve is shown as Graph 2 below.

As one can see from the above two graphs, as the calibre increases - that is, as one has to fire a heavier bullet/bomb/shall from the weapon, its rate of fire decreases as it is carrying heavier bullets.

The potential targets per strike increases with calibre obviously as more damage can be caused by more explosive content but rate of fire decreases with the calibre.

An obvious question is what should be that calibre that will give us the best PTS (destruction per round) and also overall destruction over a period of combat.

Combining PTS and ROF - The CALIBRE WITH OPTIMAL LETHALITY

If one combines the above two graphs as product of Dupuy's PTS and ROF values for specific Calibre one can get an idea or approximation of that calibre that will give us the best lethality per bomb and also over the combat of say an hour. It is reflected in the product of PTS and ROF - that is what we present below as Graph 3.

The Best Calibre in Combat - the 155mm Guns

As can be seen the combined graph of ROF x PTS for varying calibre of the weapon increases first and reaches its maximum value around 160 mm and then starts going down as calibre is increased.

This clearly indicates why the 155 mm calibre has been the most potent field/artillery Gun in different families and the underlying reason thereof. (The picture below of a 155 mm Howitzer is just for illustration purpose)

Author: Navneet Bhushan

Navneet Bhushan (Navneet) worked as a Scientist in DRDO from 1990-2000. He is founder director of CRAFITTI CONSULTING (www.crafitti.com ) – an Innovation and Intellectual Property Consulting firm focused on co-crafting solutions for global problems. He regularly writes on defence, security technology and innovation. He is the principal author of Strategic Decision Making- Applying the Analytic Hierarchy Process published by Springer-Verlag, UK, as part of the Decision Engineering Series. Navneet Blogs at https://innovationcrafting.blogspot.com.He can be contacted at navneet(dot)bhushan(at) crafitti(dot)com