Deus Ex Machina in an exploration into a fan remake and modernisation of the original in Unity, redesigning systems and game mechanics to conform to modern iterations of the franchise and the genre as a whole. Not designed to be an exact remake of the original but instead and evolution of it with the intention being at this early stage to produce a reimagined Liberty Island as a portfolio piece.
[Images from games that confuse/combine weapon handling skills and how a weapon functions]
Weapon handling abilities constitute the players ability to operate any given weapon of any given weapon type. Unlike most games relying on this as a mechanic to control the functionality and capabilities of any given weapon, in Deus Ex Machina, the skill component only affects the player's ability in handling the weapon, and not the weapon's functionality.
So what this means is that a given cartridge used in a certain weapon produces a scientifically uniform bullet trajectory, time between extracting a spent casing and time to seating the next round, time it takes to fire when a certain trigger pressure is applied to the trigger, how much force is applied for recoil per shot, weapon modifications affecting characteristics and any other characteristics that apply to how the weapon operates, given suitable simulation characteristics within the game. The player's weapon handling skill has no effect upon these types of parameters.
What the player's weapon handling skill does have an impact on is how fast they are able to reload, their accuracy with the weapon (This is not the same as just applying a firing cone to the weapon and just reducing it depending upon the players skill) and finally the amount of horizontal and vertical sway which is reduced by experience through honing muscle memory. Finally handling of recoil (is the player able to reduce the recoil so that the next shot is still on target?).
Another avenue of thought is that arm augmentations have an impact on handling too, whether it be through the ability to absorb greater amounts of force, predicting movements required to mitigate certain forces or the ability to apply weapon specific movements that enable the user to better handle the weapon in question (almost to the point of the user being able to inhumanly operate the weapon with minimal accuracy, sway and recoil deficiencies).