Yeah. Now it’d be easy to programmably trigger each charge on the order of microseconds or less, and we can make some pretty fast-shutting valves. Barrel wear is harder and would probably involve simulational fluid dynamics. More likely we’d just build a coilgun, which removes that issue very nicely, and uses similar control electronics.

Of course, if you want to destroy a city there’s also nukes now, and anything else tends to either move or be very well protected. People have talked about this for space travel, but the trade-off between G-forces and length hurts at least as much as the rocket equation (despite being “only” quadratic instead of exponential).