For the weapon proficiency "Range", it does not show on the weapons stats the details of the improvement. How much range does it add compared to how much range Silencer removes?
According to the Call of Duty wikia:
Range proficiency is only available on submachine guns and shotguns. It increases the effectiveness of the range of a player's weapon by 25% (it increases damage drop distance by 25% for the weapon; for shotguns it also increases maximum range by 25%).
The example they give using the USAS-12 shotgun is:
USAS 12's damage begins to drop at 10.5 meters and its maximum distance is nearly 17.7 meters. With Range proficiency its damage begins to drop at 13.1 meters and the maximum distance of this shotgun is increased to 22.2 meters.