Here is some info posted on another forum which makes some sense to me.
The link: http:// castboolits. gunloads.com/archive/index.php/t-5640.html
"The issue G.I. bore cleaners during the corrosive priming era were water-based. There are two commonly-encountered formulations: the first type is a brownish color and smells like creosote; the second is milky-white and is based on a water-soluble oil (Hatcher called it a 'polarizing oil'). Either of these will work to dissolve and remove the corrosive salt residue from firing corrosive-primed ammunition.
The formula given by Hatcher as having been used at SA was not an issue item, and does not contain any effective solvent of the salt, Potassium Chloride - KCl. In fact, like Hoppe's #9, it was formulated in the days before the real cause of firearms corrosion was understood (at least in the United States - the Europeans had non-corrosive priming formulae long before the problem was recognized here), and was intended to dissolve any remaining powder residue, which was then thought to be acid.
In fact, there is no readily available chemical which is even one-tenth so efficient a solvent of the salt residue as plain water, with or without additional ingredients.
Neither will formulations containing ammonia 'neutralize' the salt, which is, in fact, of neutral pH, being neither acidic nor basic. Only by dissolving and removing the salt residue can after-corrosion be prevented, and no bore cleaning compound which does not contain water can be relied on to do this.
So long as water is the most efficient, readily available and cheapest substance for the job, why not use it? All that is necessary is that the bore and parts exposed to firing residue be thoroughly swabbed (and a brush helps in the bore) with water, hot or cold, with or without additives, then thoroughly dried and oiled before being put away.
I proved to my own satisfaction that Hoppe's and other bore cleaners which are not water-based will not work to remove corrosive priming residue sufficiently to prevent after corrosion, advertising hype to the contrary notwithstanding. This was more than 40 years ago, with my first .45 auto, and when gun cleaning was MUCH more interesting to me than it is today. After a session with surplus ammo from the 1920's, I cleaned the pistol thorougly with Hoppe's, oiled it and put it away - two weeks later, when taken out, the bore was brown and fuzzy - I cleaned it again with water, and have never since suffered any after-corrosion in firearms so treated.
I recently had occasion to discuss label claims of Hoppe's in this regard with the manufacturers - after being completely unable to point to any chemical explanation of how their formula or any of its components might effectively dissolve the salt residue (which is the only way to remove it with any certainty), their response boiled down to a dependence on 'brushing and flushing' - that is, mechanical agitation and flooding - to remove the salt. This approach was thoroughly discredited more than 70 years ago.
Modern shooters are often unfamiliar with the history of the problem, and all too prone to accept that the latest and greatest commercial nostrums MUST be good for all things - I'm more sceptical, and actually did some research on chemical solvents of KCl - I'd suggest that anyone who wants to know more about exactly HOW the current commercial formulae accomplish whatever they may claim in this case should contact the manufacturer(s) and request their explanation in chemical terms. Also, you might want to do as I did, and try to find alternatives to water as a solvent of KCl: there are NO good ones.
Do what you think best, but, by all means, read the discussion of corrosion in 'Hatcher's Notebook' for the background."
This also makes sense in the context that even with this stuff available, I have heard first hand that during the time of corrosive ammo it was standard to pour boiling water down the barrel if possible.
