Proficiencies do matter. The can affect your damage, rate of fire and accuracy. The increases can range from 10 to over 100%. It has not been determined whether the increases effect the base damage of the gun or the damage which is listed on the item card. The creators of the table below have not identified what method they used to determine the increases on gun figures. They say that the maximum damage increase is around 50%, however this has yet to be confirmed.