So it was going to fire all the way around the planet on a trajectory that would, by necessity, take it directly across the Corel continent? =| You're not really buying what you're selling here are you, Ryu?
For the gun to be an effective offensive weapon AT ALL, it needs a significant range, at least the equivalent of the Atlantic Ocean.
Given its design, it by necessity must be a long range assault weapon, similar in nature to the Megacannons of WWII.
Given it was constructed during the period of war with Wutai and yet affixed on the other side of the Corel Continent, either A: ShinRa is just as fucking dumb as AVALANCE would be, or B: It does have a significant maximum range.
When it's hooked up to mako reactors and firing a beam of energy, sure. We don't really have any reason to believe it could do that when just firing shells.
Actually, we have more reason to believe shells can do that. Energy as a rule travels linearly, not in parabolic arcs.
Certainly we weren't given such a demonstration in the one scene from the original game where it was firing shells.
True, but it was also trying to fire on something in its immediate vicinity, and having significant trouble doing so. This, it's excessively long barrel, and the low amount of local range of movement suggest that. It is not a point defense weapon, it is a Long Range Assault weapon.
I mean, we are talking about a weapon with a barrel length the rough equivalent of Midgar's Radius, and a Barrel size big enough to nearly fit the Highwind in.
So yes, I kind of have to assume it's meant to be use to alpha strike extremely long range targets. Otherwise it's a pretty dumb weapon, with a limited horizontal arc, a large vertical arc, and a slow readjustment.
It's ShinRa's Death Star Superlaser, really.