The gunshield is a large square inch thick bullet proof block fitted to the front of a weapon, these can be painted camouflage or be made of transparent materials in order to keep good visablity. These can take several AP rounds before even cracking.
The gunshield can also be used as a bipod to support the weapon on any surface and when laying prone a soldier can be completely protected by the shield.
These gunshields can be made very light weight at only 3-5 pounds depending on what material is used. When moving forward, if moving crouched the shield can be kept between you and the enemy while you are still able to return fire, unlike body armour which has to be made flexible, gunshileds are made completely solid allowing much higher levels of protection.