But again totally pointless. The guns do have plenty of scenario's to be used in. If what you claim is true, then the Navy would have just built the Arsenal ship, but they didn't.
http://www.g2mil.com/SSGN%20Scandal.htm
By the way, my ship is a force multiplier in the same way an SSGN is.
-The SSGN is a Navy “Force Multiplier.” A deployed SSGN greatly increases on-station TLAM availability. Combined with the OHIO-class submarine’s proven history of high operational availability, the SSGN frees up other Naval Forces for priority tasking, such as anti-submarine warfare, controlling the airspace, and even theater ballistic missile defense. Each SSGN will spend fourteen of its remaining twenty-plus operational years after conversion forward deployed.
As for refuting my claim, there are a lot of targets around the world such as in north korea and china, which are within 320 miles. And as I said, those exotic shells I mentioned could go 700+ miles. The ram jet shells I mentioned, which the air force are testing currently. Now even if one of those shells cost the same as a tomahawk, they still deliver more destructive power on target.
Theres also the question of whether a shell could be fired sub orbital. Space is only 30 miles from sea level. So the DD(X) AGS system could indeed fire sub-orbital rounds hitting targets of over 2000 miles. There is no missile answer to this, except perhaps a more vulerable cruise missile that has less range. And that's just the tip of the ice berg, we haven't even started on rail guns yet since they haven't been perfected.