Isn't the point of rail guns that you can use any lump of feromagnetic material and it gets so mich kinetic energy that no explosives are needed? If yes, then those bullets should be really really cheap.

Rail guns have a significant issue (which doesn't appear to have been overcome yet[1], unless they're just playing misdirection) that's fairly fundamental: the gun wastes a lot of energy on tearing itself apart. The rails would much prefer to crash into each other spectacularly than to send the projectile anywhere, and you have metal turning to plasma everywhere there is contact.

It seems fairly feasible to fix the energy usage by just throwing more energy at it (and the Zumwalt demonstrates that capacity is relatively portable), but the wear on these things is going to be a massive cost even if they reduce the problem 10x from where it is now.

[1]: http://www.popularmechanics.com/military/weapons/a21174/navy...

>can use any lump of feromagnetic material and it gets so mich kinetic energy that no explosives are needed? If yes, then those bullets should be really really cheap.

it isn't explosives that costs money. A typical $3K "dumb" bomb is made "smart" by bolting-on $25K JDAM guidance kit. When Lockheed Martin is done with that "lump of feromagnetic material" you'll wish it was made of gold instead :)

No, the rail-gun projectile will be a fairly sophisticated thing. It has to have a guidance system to be able to hit things at long range, so it includes a lot of electronics. (Similar, in fact, to the projectile in the article we are commenting on now.)

But the projectile is not the most tricky part. The plan is to develop a single "hypervelocity projectile" which can be fired by both chemical and rail guns, so it seems likely that that part will work out.

The rail gun itself needs a lot more research and development to get to a usable form. See e.g. this rather pessimistic article[0]. Meanwhile, the Navy doesn't care enough about the Zuwalt guns to even buy ammunition for them. How much will they spend on building a better gun?

[0] http://www.defenseone.com/technology/2016/06/can-navys-elect...

Heard a comment from a recently deployed logistics guy: "A great projectile for a rail gun would be a used-up double-A battery - we always have plenty of those."

It's not that they can't afford shells (and they're shells, not bullets) for the guns. It just doesn't make sense. If they'd built the original 22 ships and ordered ten thousand shells the per-shell cost would be much lower.

But since the entire advantage of artillery is having the ability to put rounds on targets more cheaply than other methods, once you're paying $800k for a round you may as well use aircraft or missiles.

The railgun will probably get deployed just because it gives them capabilities far beyond AGS. It will have almost double the range and, in theory anyway, could be used against land, surface, and air targets (including ballistic missiles).

But the only ship that can carry it is the Zumwalt, there are only three of them (so the price per gun or round will be enormous), they have very little capability against air targets (because this was deleted from the Zumwalt in a previous cost-saving measure).

So a rail gun on the Zumwalt would basically do the same thing as the AGS. It would maybe have longer range, depending on how many megajoules they can make the gun output, this is still an open problem. And the magazine would have space for twice as many rounds, since they don't need to store the propellant. Given that the Navy apparently just decided that they don't even want the AGS, I don't think they care at all about the capabilities they'd get by installing railguns on the Zumwalts.

They may still install it as basically a pure research project, but if money is tight...

The AA capability of the railgun was "deleted"? Where did you hear that?

No, of the Zumwalt destroyer. Originally it was to have a "dual band" radar (an S-band search radar and an X-band tracking radar) and the capability to fire Standard Missile-2, -3, and -6. Eventually, the S-band radar was deleted and the integration work to handle the Standard Missile was not done. When the Navy cancelled the Zumwalt orders to instead produce more Arleigh Burke destroyers, Raytheon offered to do additional work to integrate the Standard Missile, but the Navy was not interested, so now the only AA weapons it carries are Sea Sparrow missiles for self-defense. This is all from Wikipedia.

I can't imagine them not doing that integration work if they add the railgun. Even if we assume it's just a technology demonstrator, they'll want to know how well it works against missiles.

OTOH, only the third one is getting the railgun if it happens at all.

As far as I understand, they're closer to missiles than to bullets: explosive, have GPS, guided, etc.