First off, thanks BI for pursuing Weapon Inertia as a mechanic to differentiate between handling characteristics of weapons. The OPREP was very informative. For the record, I wish I did not have to write this but that is ostensibly what the tracker exists for.
In the current Dev Build implementation the mechanic by which Weapon Inertia is achieved is based on the misalignment of the weapon sights based on the degree and time by which the player moves the mouse.
The problem with this is that it is neither a good representation of what inertia is as a physical force nor does it bear a good resemblance to what a real shooter sees when doing target to target transitions/tracking moving targets. As I'm sure that other people who shoot can attest to.
In particular with rifles; in reality with a proper grip and cheek weld on the stock the alignment of the sights would never significantly misalign in relationship to each other when doing either fast or sudden movements. This is because the origin of motion occurs at the end of the stock in the shooter's shoulder, forming what is effectively the pivot point behind the shooter's field of vision.
In Dev Build, this pivot point is arbitrarily occurring in the players field of vision approximately at the location of the rear sight due to the camera banking and pivoting over the stock. This execution of the mechanic is fundamentally unrealistic.
Furthermore, the mechanics of DB are such that any rotational motion whether sudden or constant misaligns the sight for the duration of motion. Of course, we also should understand that this is simply not what inertia is.
If inertia being the resistance of a physical body to a change in a state of motion then what one would expect would be resistance from the weapon in the initial movement of the mouse and a tendency for the weapon to try to keep moving in the direction of turn when the motion is halted.
In reality, tracking a moving target is easy as long as the shooter is moving the muzzle at a steady rate and doesn't run out of rotation (typically at the waist). Tracking an erratically moving target however is difficult due to weapon inertia (real inertia, not what is in Dev Build right now).
I understand that the current system is not likely to change, but given the OPREP's stated goal to trying to represent an authentic experience for small arms handling I felt compelled to point out the error.
Sight misalignment in this manner is neither authentic nor does it correctly represent inertia in any shape or form. Also in reality sight misalignment causes deflection; another fundamental marksmanship problem.
If possible, I suggest that the same values used for the current system (mass and center of gravity?) be reapplied in an actual inertia system that focuses on the resistance to changes in states of motion and not penalizing any and all movement of the mouse.
Even if the "weapon lags behind the cursor" mechanic is somewhat character assassinated in the OPREP, it is in fact a more functional representation of what weapon inertia is.
Sorry for being "That guy" this time :) Rock on BI!