I agree,dry patching the solvent from the bore is probably all thats needed.
Yeah the alcohol contains 9% water but it flashes very fast,not to mention the dry patching and oiling after using it.
Using brake cleaner opens up some concerns when using it to flush other solvents,epecially ammonia and chlorinated based solvents.
Any chlorinated solvents or otherwise could react with the trace amounts of ammonia creating hydrochloric acids etc.etc..
Most solvents do no react well together and thats why its recommended to flush the barrels with alcohol before switching solvents.
Also trace amounts of solvents can create problems with some lubricants.
And some of the brake cleaners leave a film behind just as the bore solvents.Some are even made using alcohol.
I use a patch or two dampened with alcohol and have for years.Never had a problem.
All my black powder and mauser rifles I clean with hot water and soap after firing corrosive ammo and then ammonia based solvents for the copper.Followed by a patch of alcohol,dry patch or two and then oil.
So Im not affraid of the water content as its never caused a problem.You just cant let the alcohol or water stay in the bore very long.
The chrome lined bore of an AR15 even lessens the concern of corrosion.
Thanks for the warning though.
Raymond