Raw Lineseed Oil

[painter777]

Also agree with I-44 and USGI,
This is a case where less is more.
The 'Aggressive Solvents' are to hot on original patina. They are better used after stripping metal finishes in preparation to Re-park. I can't speak for all of the above mentioned, but MEK or Lacquer Thinner work very well for final De-greasing before dropping parts in the park tank.
For just cleaning original metal finishes, I just wipe clean with light gun oil until the rags or patches are clean of grime.
Then leave a light coat on the metal both inside and out.
Same treatment to my every season hunting rifles/shotguns and muzzle loaders.
For long term storage I add a light film of light weight grease and pack away.

Don't use BLO for stock cleaning, if you do you are 1: getting some grime off but 2: you are applying a partial hard finish.

A good friend swears by Murphy's Oil Soap, I tried it a couple times and liked it but.........
My favorite for removing surface crud on a lightly grubby stock is GOJO Original hand cleaner , the original (Not the "perfumed" or abrasive type). Applied and buffed off with a soft cotton rag. Fine soft toothbrush on tight areas. Have used this for years on old stocks and antiques without harming the underlying finish.

FWIW,
Charlie-Painter777