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The best resource for information like this is the NavWeaps website. Here is their page on the 16″ 50 caliber Mk 7 guns the Iowas used:16"/50 (40.6 cm) Mark 7The actual range that could be achieved with any gun is dependent on a lot of factors, such as the maximum angle of elevation, the type of projectile being fired, the quality of the propellant, the age of the barrel, etc. Per the NavWeaps page I linked to above, assuming nominal conditions the max range for the Mark 8 armor-piercing projectile comes out to 42,345 yards (38,720m). That is just over 21 nm, or 24 statute miles.

No.I was curious about this question myself, and the other answers suggest that the US Navy’s new railgun is more powerful than the battleship guns of WW2. After some quick calculations, I was surprised to find that this is absolutely untrue.If we define ‘power’ as how much kinetic energy a projectile has, then a WW2 battleship gun is by far the more powerful. No modern gun comes close.Take the US Navy’s 16″/50 Mark 7 gun, for instance, nine of which can be found on each Iowa-class battleship. The Mark 8 ‘superheavy’ APC shell it fires weighs 1,225 kg, and leaves the barrel at a velocity of 762 metres per second. That shell leaving the barrel in the picture weighs just a bit more than a Toyota Corolla.Running these numbers through the formula for calculating kinetic energy… E = 0.5 x mv^2… gives us a whopping 355.6 megajoules of energy per shell.On the other hand, BAE’s railgun in 2008 was tested at only 10.64 MJ firing a 3.2 kg test projectile at 2,520 metres per second. According to Navweaps, a new launcher under development is expected to be rated for 30 MJ shots, while a future design for production is expected to fire saboted rounds with 63 MJ of energy at the barrel.So, WW2-era 16″ battleship guns fired projectiles with over 11 times more muzzle energy (355.6 MJ) than the 32 megajoule railgun that BAE was contracted to build for the US Navy’s Office of Naval Research. The battleship gun wins this ‘which is more powerful’ contest, hands down.Moreover, each 16″ Mark 8 APC shell came with a 18.6 kg bursting charge, designed to explode after the shell penetrates the armor of its target. A railgun slug is completely solid and does not have as spectacular a design. So, you can easily demolish a building with an exploding battleship shell, but not a railgun slug as that would just fly right through.However. it must be said that the railgun slug is much smaller and faster than a WW2 gun shell. This gives a railgun more range and a higher rate of fire over a WW2 battleship gun, and is a far more suitable weapon against modern warships than a battleship gun would ever be.

Projectiles from guns can be stopped by air defence. “It flies, it dies” as Type 45 AWOs are wont to say. However, that’s inefficient to use expensive missiles to damage and divert cheap shells enough that they fail to do damage.A bigger problem is that, without guidance, projectiles from guns are really poor at hitting ships. To take the accuracy figures from 16"/50 (40.6 cm) Mark 7 -at NavWeaps, under good conditions and against a broadside battleship-sized target at 30,000 yards, an Iowa-class battleship could expect to fire forty shells to get one hit.For smaller targets, of course, it would be worse, and the assumption back then was that both ships were holding steady courses to let their fire control computers calculate good solutions, because the magnificently engineered mechanical systems of the day couldn’t cope with own-ship manoeuvre (naval fire control, in the Dreadnought era, was the Space Race of its day) Modern ships, not trying to let their gunnery solution settle, can jink and dodge and evade at will.But a Harpoon missile will reliably hit its target at six times that range unless decoyed or intercepted, and while that’s entirely possible it’s expensive and difficult to be able to do so reliably; and it strikes with several times the destructive force of a 16″ gun (the shells were huge, heavy, and mostly dead metal)And at the sort of ranges seen today, assuming a battleship could get an enemy into extreme gun range, they’d be depending on radar to target, just as a missile would depend on radar to guide: you don’t need to “stop the shell”, you just jam its fire-control radar, or feed it errors so it’s firing at the wrong patch of ocean.As with air combat, guns for ship-to-ship combat are obsolete because they depend on the same sensors as missiles, yet are much shorter-ranged and less lethal. Guns have other, valuable uses… but not for dogfighting aircraft or ship-to-ship combat between battle fleets.