Ephiral's point about maintenanc s a very gd one. yes, cannon artillery is very robust compared to Missiles. But thee is the ammunition to consider. Do the NKs everytrow anything away? A chunk of their ammo stockpile will dat back to the 1950's. How reliable is the proppellant, the fuses, the payload charges themselves?
But with 10,000 tubes in range of Seoul, they could still deliver up to one kiloton of high explosive to the city per hour.
here's a chilling thought:
Most people seem to think that a new round of fighting will be a repeat of 1950, with the North Korean Peoples Army blasing across the border en masse.
What if they have something more subtle in mind?
Here is my personal worst-case scenarios - and I did not come up with this, I got this from a talking head on TV some years ago:
At midnight of the appointed day, they open up on Seoul with everything they think can reach it.
And then they sit tight. Well, except for their Special Forces units. Which are not that special by Western standards, according to sites like Strategypage.com, their "special" forces are no better trained than "regular" Unites States Army Infantry. Which means the NKPA regular troops are basicaly cannon fodder.
But back to the plan:
1. They start shooting, their Speical forces lunge into South Korean rear areas to raise hell - and there are something like 110,000 of them, so some will get through and a lot of hell will be raised.
2. The South Korean and American armies attack. They have to, they have to, to stop that artillery barrage. Those guns, many of them seem to be very well dug in, destroying them will take time and, well, one kiloton per hour and all that. Yes, as guns are destroyed the bombardment will ease... but asking South Korean civilians to gut it out and take it will not be an option, really it will not.
3. The NKPA rides out the attack, lets the enemy smash itself on the border defenses - then counterpunches with a general counteroffensive - and this time they keep an eye on places like Inchon.
That may be their plan, anyway. I think once the NKPA offers actual battle in the field, it will be be very quickly ground into mincemeat and iron filings even if Allied airpower is preoccupied with silencing the guns bombarding Seoul. And as to NK fortifications, well, the Allies know how to deal with those, they will not be impenetrable.