This is the Bandai Customize Weapons (Heavy Weapon 2) 30MM [5067159]

A heavy weapon set is now available for "30MM (30 Minutes Missions)" and other 1/144-scale model kits from Bandai! The hard points attached to the weapons and the abundant joint parts allow you to enjoy a wide range of customization possibilities. The radome and rifle can be connected to the backpack; the rifle has a movable bipod, and gun barrel parts (sold separately) can also be connected. The link belt is made of soft material, and can be attached to a backpack