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Friction and the Firearm

Disclaimer: The study of tribology (lubrication) is largely theoretical observed science and subject to empirical testing.


Friction measures the resistance at the interface between surfaces and is either static or dynamic. Static friction is affected primarily by surface smoothness, whereas, Dynamic friction adds motion, pressure, heat and lube properties to the equation. CoF, or coefficient of friction is the result of measuring friction and can be used to compare the relative performance between lubricants. To put it simply,

µ = CoF

The numerator is the amount of applied sheer force at the interface and the denominator is sheer strength at the interface. [1]Sheer force can be anything from the weight of gravity to some known applied force. In the case of firearms, sheer strength measures the ‘resistance’ force between the two moving parts and may range from ‘surface only’ force to lubricant, contaminants, fouling, decomposing mixtures of lube/powder fouling, cleaning product residues, etc.

There are a variety of lubrication tests, but for firearms, we need to evaluate wherestatic and dynamic friction occurs. Any moving part in a firearm is subject to friction. This includes bolts, triggers, levers, pins, springs and hammers.


Static friction is evaluated when firearms are function tested, features are cycled or specific parts are visually inspected after periods of inactivity, such as storage. If firearms are not ‘clean’, or if there is contamination between moving parts, static friction can be evident. If there is enough static friction to impede the normal operation of moving parts, a malfunction may result.

If static friction occurs, the best way to resolve the problem is to do a thorough ‘clean’ of affected moving parts. Use of a ‘degreasing’ solvent is mandatory. If the source of friction is internal, the correction may require immersion or flushing out of the internal spaces. In the worst case, the firearm may have to be disassembled. Alwaysverify the source of static friction has been removed before reapplying lube.


The first consideration is the surface smoothness of the two parts in contact. Metal surface is irregular and its irregularity is a measure of the size of the ‘asperities’ (differences in peaks and valleys of material surface) measured in RA or RMS.


Further, the surfaces in contact may also be affected by lubricant placed between the moving parts. This is called either ‘boundary lubrication’, ‘hydrodynamic’ or a ‘mixture’ of both.



There are other friction forces acting on firearms that need to be accounted for. They all act on the same interface between the moving parts to varying degrees. Here are some;

- Material surface

- Pressure

- Heat

- Lube Elasticity

A lubricant formulation has to address these forces while at the same time, not impact on the mechanical action or designed ballistics. In conclusion, the end result of an effective lube is 100% function, ‘zero malfunctions’ attributable to lube or fouling and no impact on designed ballistics.


[1]Nat’l Program on Enhanced Tech Learning NPETL, Tribology module

[2]NEPTL, Load sharing module


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