I say let them make it. If actually understanding technology has any impact, they might make a faster bullet, but as soon as they put some explosives in it, it will surely explode upon firing. talk about collateral damage and friendly fire!
Let them take them out themselves. I cant imagine them being able to make a firing mechanism that can survive being shot out of a rail gun and still explode when it reaches the target.
FIRE: (Another one of them bites the dust because the firing-pin thought it hit something.)
N.Korean firing officer: Ah,Shi-bal, I think I will defect now.
rail gunn ammo is kinetic energy based no explossive round is required, similar to gravitational bombardment.
still, not enough energy and no material being sturdy enough to actually use it in any sensible form makes it inviable.