U.S. Navy to test futuristic, super-fast gun at sea in 2016

Yahoo/Reuters ^ | 4-7-14 | David Alexander

[Freeport]

Correct, but at Mach 7, your through the first 20,000 feet of thick air in about 2.5 seconds at 7813 ft./sec: 7 times the speed of sound at standard temperature and pressure at sea-level (761 mph). A little less since the speed of sound changes as the air density falls due to altitude.

After that, the drag doesn't pick back up to appreciable levels until it's reentering thick air again.

So the 100 nautical mile range is not far fetched.

And if for some reason your within line of sight... you're toast almost before you see the plasma flash as the projectile leaves the barrel.