The B-76 Self-Propelled Gun is based on the South African Denel G6, a self-propelled artillery platform for the G5 Howitzer. There are no different variants of the vehicle in the either real world or in Just Cause: Volosia.
Designed as a means of long-range artillery bombardment when aircraft are not available or not practical, the B-76 Self-Propelled Gun is designed to balance speed, mobility, and firepower in one package, sacrificing armor for these capabilities. While it does not pack the strongest punch of the cannon-based self-propelled artillery vehicles in Just Cause: Volosia, it is certainly the most mobile, and the fastest. It has low armor and is unable to withstand a direct hit from a tank shell, but Black Hand tactics ensure that the vehicle is escorted by tanks on the ground and/or helicopters in the air before any real threats can reach the vehicle. It is excellent for striking hostile bases from afar, and in large numbers with proper protection it can tear apart enemy armies in minutes. If absolutely necessary, or if its defenders have been destroyed, the vehicle can also deploy smoke grenades to create a smoke screen and escape danger quickly.