Daryl,
I still use hot water and non-petroleum lubes.
Not spotless barrels but no corrosion either.
I have never tried WD40 for fear of problems with powder residues. One of my rifles have been some years into the gun safe only with natural lube (commercial lube made locally) and still is perfect without corrosion. I can shot all day without cleaning.
I will have to try WD40 some day.
Thanks
Martin