In 1993 a C.I.P. specification was adopted covering special proof for guns which can be used with steel shot. The specification lays down shot size and hardness, the number of proof rounds to be fired through each barrel and the pressure to be generated at 25mm and 162mm. A special "Steel Shot" proof mark will be stamped on each barrel of such weapons that have successfully been proved.
If mishandled or neglected, a gun may be damaged or weakened, even in a short period of service. In such circumstances work necessary to return it to serviceable condition, may render invalid the original proof marks.
Indications of weakness may only be apparent to those trained to recognise them. For that reason, inspection of guns by a gunmaker, at regular intervals, is recommended, and advice to submit for reproof should be followed without delay to avoid undue risk of personal injury.
Guns are submitted to reproof at the owner's risk and the gunmaker is entitled to payment for his work, regardless of the result of proof. Guns will not be accepted for reproof, if it is the decision of the gunmaker that they are not in a fit condition to be proved.