The cannon-powder for proof shall be of not less than 1,500 feet initial velocity, as determined by the gun-pendulum at the Ordnance Yard, Washington.
It shall be filled in service cylinders, and well settled.
For chambered pieces the increased charges should fill the chamber and necessary portion of the bore.
The projectiles shall be of full weight, and not below the mean gauge; the shells shall be filled with a mixture of sand and ashes, to bring them up to the proper weight of the filled shell.
Sabots for the shell and a gromet wad over the shot.
The gun should be fired on skids or a proving-carriage, to test the trunnions.
If five per cent. out of any lot offered for ordinary proof under a contract shall fail to sustain it, the whole may be rejected, as may be stipulated in the contract.
WATER-PROOF.
32. The pressure to be applied in the water-proof will be two atmospheres, or thirty pounds to the square inch.
The penetration of water in this proof through the metal of the piece, in any place, will cause the rejection of the gun; and if, on examination after the water-proof, there shall be any defects indicated by weeping or dampness in the bore, the gun shall be rejected.