The gun is here.
[Description] This weapon was made specially for Mobile rO81-CS. Does a little less damage than Vehicle Cannon, but have more accuracy and fire rate. It can be used as mounted weapon or can be transferred and used manually without special devices. For these purposes two fastenings are made. The first on the top and the second from inside with trigger. Also the weapon has gravitational quencher and respectively unusually small recoil. However, it is very heavy and for its transfer is required a high-class exosuit. Considering caliber capacity, the ammo box holds 150 bullets without additional ammunition supply.
[My suggestions] This weapon can be removed from the vehicles and it can be used by one heavy character or two lites. It can't be removed in inventory and it reduces mobility, also you can't duck. Being on a vehicle or mounted the weapon has a large number of bullets, but after removal their quantity decreases to 150.