Only an experienced barrel specialist, with a bore scope and wall thickness gauge, could provide an opinion as to using the barrels. And it is a challenge to get the wall thickness gauge pin in the bottom of a pit.
That said, by 18" the pressures of today's loads are < 1000 psi.
Send the barrels to Dean Harris at Skeets Gun Shop in Tahlequah, OK
918-456-4749

I would add that I've been surprised to find honing as little as .002 or so can remove pits that visually appear fairly deep. 12g hammer guns have substantial barrel thickness.

If you send the barrel to a barrel guy please let us know what he thinks.