The actual damage of a weapon does not correspond to the parameters.

I'll give a few specific examples. I think the problem is similar for almost all weapons.

1) NVO-228E. Damage: 33. Stock velocity: 671.
Even to the first target (10 meters), it only deals 27 damage. To the second target, it deals 27 (if standing directly in front of it) or 21 (if shooting from the side).
Moreover, installing an extended barrel, which increases velocity, doesn't affect the result at all.

The AK4D, with a lower stock velocity (720) than the NVO-228E with an extended barrel (838), actually deals 33 damage to the first two targets (the second one deals 33 damage if you stand directly in front of it).

2) SCW-10. Stats say 33 damage. 428 velocity with a standard barrel and 528 with an extended barrel.
In reality, it only deals 25 damage to the first target (even with an extended barrel). The second target deals 20 damage (25 if you stand directly opposite).

3) PW7A2. Stats say 16 damage, 600 velocity.
Deals (!!!) 17 damage to the first target. Even more than the stats indicate. Deals 14 damage to the second target (17 if you stand directly in front of the target).

4) SVK-8.6. Damage 66. Velocity 900.
Even to the first target, it only deals 60 damage. To the third, it deals 50 damage.

How is this possible? The PW7A2 deals more damage than the stats indicate, yet its velocity is lower than that of the NVO-228E or SVK-8.6, which already have a severe damage penalty even to the first target.

What does damage range actually depend on? Why do most guns have a damage penalty even to the first target (10 meters)? Why do weapons with higher velocity have a penalty, but those with lower velocity don't? Why doesn't increasing barrel velocity reduce damage drop? How can the PW7A2 have more damage than stated?