This area of endeavor addresses the exact metallurgical composition of each and every part of the firearm. Parts may be optimized for their function by changing the alloy and hardness. This further branches out into the use of polymers and other man made materials for use in firearms.
As an expert in this area, LTC Alphin submitted change improvements in the M-85 caliber .50 machine gun mounted in the M-60 family of tanks. Specifically, there is a part in the gun called the “Jesus” pin because “…if this thing breaks, by Jesus, this gun won’t work…”. LTC Alphin’s recommendation went to a different alloy and double heat treatment process which retained the strength of the pin but led to greatly decreased breakage.