All through my shooting life I was taught that 3 in 1 oil was too thin to be a good gun oil and was told NEVER to use it. Never heard of it as a cleaner.
While great for light duty precision mechanical devices, like typewriters, sewing machines, fishing reels, and things like that 3 in 1 has really poor thermal properties. Exposed to heat it will cook off quickly. It'd be OK I guess for internal parts but I wouldn't use it on slides / rails / bushings. It does not gum up so it might be great in revolver lock works but being very low viscosity it will tend to all run out.
There's better choices.
A lot of people don't realize that 3 in 1 is the original "CLP". The 3 is for 3 uses in 1 oil..... "Clean, Lubricate, Protect"3 in 1 is a light machine oil, made for lubricating machines...sewing machines , electric motors and such. Developed in 1894 an old school CLP. Cleans lubricates and protects long before Shooters Choice hit the market . It is a LIGHT oil and will dissipate but It doesn't go gummy and is great for firearms and trigger . just apply often .
I've used it for years along with Rem-Oil. Most shooter want to buy expensive super dooper lubes thinking it better but I haven't experienced it.
Some other good lubes...Mobile 1 synthetic , a 50-50 mix of ATF and kerosene , ATF is a good lube but I like it thinner , use out the bottle for a heavier oil. Note I like regular General Motors ATF (not synthetic) , synthetic will not mix with kerosene or mineral spirits . Google Ed's Red Bore Cleaner for a good recipe for bore cleaner and lubricant .
ATF , automotive motor oils and synthetic two stroke oils have very good thermal properties...motors and transmissions get hot !