Gentlemen: PLEASE. READ MY WORDS CAREFULLY. I was asked what the problem is with using BOILING water-- Not hot water-- not warm water.
If you dry the barrel quickly when its removed from hot water, you can generally avoid flash rusting.
Yes, Flash rusting is not the end of the world- Once. But over many repeated instances of flash rusting, you do begin to see evidence that the smooth surface of the lands and grooves are beginning to fail- pits, and rough spot. Some of these can be dealt with by using lapping compounds, or various abrasives.
But why not avoid the problem by simply using TEPID water? It is just as much a " solvent" as BOILING WATER IS. I used to clean with the hottest water my hands could stand, and dealt with flash rust time after time. I was " Converted" by a wiser shooter than me, to using only Tepid Water( and soap) to clean my gun. I found it not only cleaned the barrel thoroughly, and just as good as my formerly used HOT-HOT-HOT water, but because I didn't have to remove the flash rust, I also didn't have to spend that extra time cleaning after each shoot. My cleaning time dropped in half or more, to the point my wife began to ask me if I had actually cleaned my gun. :hmm: :surrender: :thumbsup: