Just some Logical ideas to improve this.
Heavy machine guns accuracy should be penalized while moving with and without sights in combat pace in real life a heavy gun like that would jump every where due to it's very wight and long barrel, also the alignment of the weapon sights should take longer since the gun is heavy and due to it's longer barrel.
This Idea should also be applied to Light Machine guns and marksman rifles, these guns are much heavier and have much longer barrel thus the weapons accuracy should be penalized while moving in combat pace, the alignment of weapon sights should take longer while moving and also in combat pace.