Gary, although this has been discussed several times before, I think it's an important topic. For one thing, I certainly don't have all the answers, but I have been shooting and necessarily cleaning muzzle loading guns for over forty years. During that time, I have gone through various procedures and have watched others' efforts too. I have had to replace barrels on other people's guns for lack of proper cleaning. And I've made some observations that I hope will help others avoid oxidation inside and outside their rifles.
The following is my own opinion based not on any known scientific principles; just observation and common sense. Water is all that is needed to dissolve black powder fouling. The trouble with hot water, and especially boiling hot water, is the very reason it is used. The steel being very hot, dries the water completely out of the steel instantly. But it causes FLASH RUSTING! Rust is cancer to iron and steel. It does not go away with a wipe and a soak with oil. And every time you repeat this cleaning method, you flash rust again and again. This creates pits in the bore, and they eventually are noticeable when loading, and cleaning becomes more and more tedious and difficult.
Cold water flushes fouling as well or arguably better than hot water. And running several flannelette patches one after the other down the bore with a faily tight jagged cleaning rod, dries the bore. The first patch will come out grey/black and damp, in spite of there being no fouling remaining in the bore. I suspect that this is steel and oxide on the patch. The next patch also will come out greyish, but not nearly as dark and the first, and a lot drier. Four patches later, the patches are becoming very difficult to withdraw as they fold back on themselves behind the jag, but they will come out dry and white.
I use a stainless steel cleaning rod with a stout handle. My jags I've reduced in diameter so I can use a doubled flannelette patch, which goes to the bottom of the grooves. A single layer of cloth I find, does not. And if I'm doing the cleaning in the shop, I put my barrel into my padded vise, so I can use both hands and some power to scrub it out thoroughly. In hunting or rendezvous camp, though I still use a steel rod, I use thinner material, or a smaller jag, because I don't have the luxury of a vise.
So, once it's dry, I squirt about three shots of WD 40 into the muzzle, wet a dry patch, place a rag hanging over the vent to catch the spray, and shove the patch down to the breech. Excess oil shoots out of the vent, hopefully taking with it any water left behind in the corners. I oil the outside of the barrel with the same patch, and stand it on it's muzzle while I clean the lock.
I do not usually disassemble the lock. I dunk the whole lock into the same water I cleaned the barrel with, and with a toothbrush, clean away all the black fouling. I have a compressor, which drives my dogs nuts for some reason, to blow the water off the lock. I place the lock on a rag in my hand, squirt it in and out with WD 40, and repeat the blow job. I phrased it thus to see who's reading this. I notice that cleaning the lock in the same water increases the blackness of the water by perhaps four times that that was flushed out of the bore. The water before cleaning the lock was just barely discoloured by the fouling, and now it is very much blacker.
I wipe down the wood with a wet patch around the lock, then dry it with a towel. I reassemble the gun, and stand it on its muzzle in the gun room. Over the years, a very small amount of oil has accumulated on the board on which the muzzles sit, but I'd rather it there that plugging the vent, or worse, running out onto and into the wood around the breech and lock.
This entire process takes me from 20 - 30 minutes, and I know when I'm finished, the rifle is every bit as clean as when I left for the trail.
All this having been said, I am willing to listen to what others experience may have taught them. I love to learn new stuff...the fact that I used to use hot water is testimony to that.
A year or so ago, someone posted a method of using a garden hose to pressure wash the bore of his rifle without removing it from the stock. I thought that was pretty ingenious.
