Mike George

A lot of this discolouration is caused by sweaty hands and any reasonably fine metal polish should do the trick – something like Brasso on a soft cloth, or the sort in which the polish is absorbed in cotton wool.

Remember, however, that it is an abrasive, and it doesn’t do woodwork any good, so be careful when cleaning a shotgun.

For these reasons I’d remove the stock, and be very careful to see that the polish doesn’t get inside the action.