I took my Boswell to a local gunsmith to check out the loose action. He commented that the degree of movement when the gun barrels are moved laterally with the forend off is quite minimal. Considering the amount of use I give the gun, he said it will be many years before it becomes an issue. He suggested using light trap ammunition as a means of extending its life further and applying grease to the hinge pin. He replaced both firing pin springs as I've had an occasional misfire, mainly when using reloads. The original box lock springs were considerably more closed at the open end compared to the new ones he fitted. Thanks to all for your input.
