Why should old military Mauser actions not be lapped?

Lapping old military Mauser actions is discouraged because it can compromise the case hardening of the metal. Case hardening is a process that hardens the surface of the metal, providing greater durability and resistance to wear. The Mauser actions were designed with this hardening to maintain integrity under operational conditions. When you lap the surface, you are effectively removing material, which can alter the properties of the hardened exterior and expose the softer underlying metal. This can lead to increased wear and potential functional issues in the long term. Preserving the integrity of the case hardening is crucial for maintaining the reliability and longevity of the rifle.