I absolutely care whether or not a gun is in proof. I am concerned about safety and realize I am the final arbiter of safety every time I choose to trip the trigger. However, proof is an institution with laws and regulations and should not be so easily dismissed. There are reasons that the British have proof laws and proof houses. I choose not to buy a gun that is out of proof and that affects the gun's value. Here in the U.S. everyone is free to make their own choices, but to me the value of a gun is negatively influenced by alterations that take it out of proof. Now, whether or not messing with the forcing cones takes a gun out of proof is for others to decide. I'm of the opinion that removing metal from the barrel does invalidate the proof. Others may think differently.