This particular VHCT-12, serving in the 75th Armor, used to run in a large supply convoy transporting finished weapons and vehicles to the front lines. Because of its importance, the convoy was always being ambushed and harrased by enemy forces. The commanders made constant requests for reinforcements, but the fighting vehicles were deemed to be better used on the front lines. In response, the crew of this VHCT-12 (and others) scrounged up weapons and armor and made their own convoy protection. This crew made a lucky find: an EMC-17 Gauss cannon, which can take out armor with relative impunity.
The front bumper has been reinforced and can be effectively used as a battering ram.
In the front left corner of the bed, there is a RMLS-7 turret that is controlled from within the VHCT-12, in the passenger seat. The onboard AI can also control this weapon for greater effects.
Here is the manually operated twin AC-3 20mm turret, good for mowing down infantry and light armor. It has a special reticule that compensates for lead and windage, greatly increasing the range.
A little .50 cal for moping up survivors of the other weapons. Also prevents hijacking.
The main gun is an EMC-17 2.5 cm Gauss cannon. It was a lucky find by the crew, almost as impressive as the salvaged reactor that powers it. It destroys tanks on a regular basis, and provides overwhelming supressive fire.
Its sensor has no need to compensate for lead or windage.
The reactor and cannon controls.
The beefed up suspension to carry the extra weight.
From left to right: Driver, missile turret gunner, .50 cal gunner, 20mm gunner, and Gauss cannon gunner.
Awesome! It looks like it'd do great as a slightly-more-futuristic non-rundown apocalypse vehicle. I've never been a big fan of Gauss weapons (as opposed to railguns) due to being somewhat unreliable, less effective, and a bit too complicated, but that doesn't retract from the vehicle's overall aura of awesomeness.