3,000t of current batteries or 150t of fuel could accelerate 10t payload to 20 km/s
(72000 km/hr). This is the kinetic energy of 10tons at 20km/s is 4 terajoules.
(1000tons of TNT equivalent)
One megaton is equivalent to 4.18 x 10**15 joules
You could create deep penetrating bunker busters based on kinetic energy.
If more of a runway was needed to accelerate, then the magbeam could accelerate the missile and have the missile slingshot around the moon or the sun. By going around the sun it would further accelerate. A shorter runway could be obtained by positioning it at a lagrange point.
By having the accelerated thing be a carbon protected object with a deployable carbon solar sail. It would further accelerate as it slingshot around the sun. the pluto probe is getting a 21km/s boost from Jupiter slingshot
Getting 10 times faster 100X the energy.
50 km/s 25 TJ 6250 tons of TNT
200km/s 400 TJ 100,000tons of TNT
2000km/s 40,000TJ 10 megatons
20000km/s 4,000,000TJ 1000 megatons
Ultralight solar sails can accelerate a spaceship to 13% of lightspeed on page 16. Nanotech could make such high performance solar sails.
Another conservative near term interstellar space vehicle concept study suggests a way to get to 950km/s.