ECM could be fantastic and practical as a way to help missiles get to their targets.
Um, isn't ECM supposed to prevent missiles from getting to you?
It works both ways. Your missiles or their drone buses can have ECM.
Precisely. And did you read the post? A good laser will blow through a meter of it (a meter!) in a second at knife fight range.
1 meter. And you have to keep the laser pointing at the same spot for a full second. A enemy ship can move by a considerable ammount within a second.
And 5000 klicks is nothing. If you have lasers, getting that close is suicidal - you just make enemy mass driver more accurate.
One meter is a
****-ton of armor. One second is barely anything in space warfare, where you'll know the enemy's precise vector minutes or hours in advance. And keeping the laser on the target is a trivial challenge compared to intercepting it with a KEW. Remember, the laser moves at lightspeed. The KEW moves at ****-all.
Furthermore, it's been said again and again that lasers are
knife-fight weapons, so yes, 5000 klicks is indeed nothing. If you continue to show evidence that you do not read other people's posts then you'll get monkeyed again.
Why? That's farcically ineffective. It can reach a tiny fraction of the range a missile can and it'll almost certainly never hit. Why not just fire a missile from the railgun?
Unlike lasers, KEWs are slow. Unlike missiles, they can't adjust course or coast-until-burn to engage a maneuvering target.
KEWs make a lot of sense using the ideal contact ellipse concept NGTM-1R outlined, though.
Innefective? Quite the contrary.
Missiles are more expensive and their powerfull engines burning make them stand out and very easily detectable. They are also bigger by their very nature, so you can carry less of them.
This argument was originally put forth in the 40s by Willy Ley. It was annihilated. You're already proposing firing a missile (guided projectile or 'smart bullet') from your railgun. And you have to. Because at interplanetary speeds, the target will have moved, on average,
three miles between the time the weapon was fired and the time the projectile reached the end of the barrel.
A KEW is effective at tiny, tiny ranges. A missile can fly across solar systems. It can cruise like a bullet and then adjust its course to intercept. You're going to need a lot of bullets, not to mention a huge railgun, to get near the effectiveness of a single missile.
Your problem isn't that you think KEWs are effective - they are. Your problem is that you're using them wrong. There is absolutely no reason for fancy, high-tech smart bullets. All you need to do is throw a beer can into the target's path to ruin his day. The muzzle velocity of the weapon will be trivial compared to the intercept velocity with an enemy ship.
KEWs are great. But they will never be as good at knife-fighting as lasers (too slow, they miss too much) and they will certainly never be as important as a ship's primary weapon: the drone, the kill vehicle, the missile. They have a place as area-denial, ideal contact ellipse weapons, dust that you spew into the target's path. They could also work well for point defense (though a laser/particle beam can knock out target electronics without having to waste time on actually blasting through.)
I always wonder why you don't make the same arguments against other weapons.
If an enemy ship can move fast enough so that lasers have difficulty handling aiming, what does that say about other weapons whose ammunitions travel at sub-light speeds? 
Yeah, exactly. Keeping a laser aimed at an enemy vessel for one second is trivial compared to keeping your weapon barrel pointed at a target ship's predicted position as it alters vector for long enough to fire, and then actually getting your slow-as-balls projectile to the target. Even adding thrusters to make a 'smart bullet' is fundamentally silly because in order to have thrusters
and fuel that can match the acceleration of the target you'll be firing a mini-missile instead of a cheap beer can projectile.
