Someone rust bluing and or composite barrel refinishing won't know postively if the barrels didn't leak. Only sure fire way of knowing is drilling a small hole up next to the barrel flats. Then actually poring a small amount of water in the hole, using compressed air blow through the hole that was drilled. You will see where if any leaks are. They can be very tiny pin holes along the rib. If no leaks the water will be blown back out through the drilled hole.
After that its a good idea to heat the barrels to evaporate any water/moisture left between the ribs.
