Underbarrels are a type of attatchment that are available for certain guns on Apocalypse Rising. The three underbarrel attatchments are the Forward Grip, the Flashlight Attachment, and the Laser Sight. But later on in the future there will be more types of underbarrels as this was confirmed by Gusmanak.
Underbarrels improve the gun's statistics as well as provide an advantage in combat.
Laser Sight - This underbarrel increases your hipfire accuracy as well as ADS (Aim Down Sights) Accuracy. This cannot be toggled and it doesn't have a laser pointing out which means players won't notice it. It's best to use this for CQC weapons and also Battle Rifles if you tend to use them CQC like the FAL. This underbarrel is considered the best underbarrel attachment and one of the best attachments in-game.
Forward Grip - This underbarrel reduces your recoil in the game. It's best to use this attachment if you have trouble controlling recoil and like to snipe a lot. However if you are a CQC guy, it's best to leave this alone or give it to a friend who needs it. If you are going to use it, it's best to use it on the STANAG Assault Rifles and the Battle Rifles.
Flashlight Attachment - This underbarrel just is a flashlight but for your weapon. This is considered the most useless attachment in the game as it provides no tactical advantage but only gives off a ray of light similar to a survival flashlight. This attachment can be a disadvantage if you like playing stealth. If you do choose to play stealth, it's best not to use this attachment. It's only a good idea to carry this attachment if you cannot find a flashlight (Fairly easy to find) or want to save utility space.