The first Balaur is mounted in the mid-section of the Spiridus's airframe. The weapon first saw action in battle during Valahia's initial assault on the Japanese capital of Tokyo, where it was used to rip open a massive hole in the harbor area of the city, thus demonstrating the Spiridus's combat capabilities. After the battle, the fortress would retreat from Tokyo towards the Izu Isands, where visual contact was lost.
A second, stand-alone version of the Balaur was stationed at the Valahian headquarters located in southern Romania. The weapon fires with the assistance of a radar network disguised as a weather station in the Serbian mountains, thus increasing it's accuracy over long ranges, it is possible that the Infern Balaur may have intercontinental firing range, due to the distance between south Romania & Serbia.
The Balaur railgun has an immense destructive power, as proven by the attack on Tokyo, where it would be used to obliterate the harbor section of the metropolis. Likewise, the Infern Balaur is just as powerful, with the shockwave generated by the firing burst being enough to annihilate any aircraft flying too close to the cannon (although the F-22 could survive at most 2 hits and most other military aircraft could survive at most 1, for proof try doing any mission that includes the balaur and allow it to hit you, do not allow anything else to hit you prior). Furthermore, the Serbian radar network allowed for precise firing over long ranges.
The Spiridus Balaur has several disadvantages: first of all, the Spiridus contains a heat vent in the rear of the mainframe, which can cause the Balaur's charging to destabilize, and can potentially lead to damage from overloading-- this was used by the M42 Antares Squadron to their advantage, dealing severe damage to the Spiridus, and in turn forcing it to retreat from Tokyo.
The Infern Balaur also has some disadvantages: to be specific, it's long-range accuracy is reduced if the Serbian radar systems are knocked out or if an enemy plane is flying very fast near it, however it remains as deadly as always in mid-to-short range or an accidental collision of the barrel.