From S&W revolver manual:
After the cleaning, there may be some residue in both the barrel and cylinder that works out and becomes apparent within 24-48 hours. This can be removed with a bristle brush and a light reapplication of powder removing solvent after which the oil film should be re-established on all surfaces.
From S&W M&P manual:
After cleaning, lightly coat the metal parts, internal and external with a high quality gun oil
From Ruger Pistol manual:
After cleaning, run a dry patch through the bore, then follow with a patch that is very lightly oiled.
From SigArms manual:
Lightly lubricate the barrel, inside and out, with a quality lubricant designed for firearms.
From Taurus Pistol manual:
For normal cleaning of handgun not used or kept in storage for some time, it is necessary to rub it with a lightly oiled cloth. In the same way proceed with the bore of the barrel. The excess of oil must be removed, but a thin protecting film should remain.
I cannot find any manufacturer that recommends NO oil in the barrel. Some have cautions against EXCESS oil in the barrel and some don't touch the subject at all or the wording of their instructions are ambiguous at best. However, as shown in the examples above, most of the manufacturers instruct to leave a light coating of oil even in the barrel. In almost 40 years of shooting this is what I've done and have never had a problem with the amount of oil in a barrel nor have I ever had a bore develop any rust or pitting. JMHO