Proof charges and testing naval guns to destruction

Can sustained firing compromise a large gun's heat treatment?

Yes. Tests can overheat barrels enough to compromise their heat treatment; overload proof and destructive trials separately establish how much stress a gun can safely withstand.

Sustained firing can build enough heat to compromise a gun's heat treatment, and testing can deliberately reach that point. Acceptance proof uses a charge above the service load; a barrel that survives without apparent damage receives its proof mark. Roughly twice the service charge is given as a rule of thumb, without a gun-specific standard. Separate destructive trials establish the limits of the design. Dahlgren's guns illustrate the effect of recent failures on engineering choices: a spate of US Navy gun explosions encouraged unusually heavy safety margins. Monitor initially used an acceptable charge, and later testing showed that the guns could take more.