John Browning apparently began designing the Superposed (Over/Under) shotgun in 1922. It was his last firearm design and a labor of love. He conceived it as the last gun the government would ban from private ownership. Like most John Browning guns it is a complicated design. The great man never used one part when two or three could be made to work. On the other hand, those parts are lightly stressed and, like most Browning designs, Superposed shotguns are very reliable.
It was Browning's intention that the Superposed be the first affordable (by the average working man if he was willing to save for it) O/U shotgun. Previous O/U designs were bespoke guns built to order for the gentry. This goal was met when the gun was introduced, and the Superposed stayed reasonably affordable until the 1960's, by which time rising Belgian labor costs (the gun was made by FN in Belgium) began to price it out of the market. In 1975 the Superposed was dropped from the regular Browning catalog due to the effects of inflation, but it is offered to this day in a myriad of grades or as a completely bespoke gun from the FN Custom Shop.
John Browning passed away in November of 1926, before some of the final details of the gun, in particular the single selective trigger mechanism that he wanted for the Superposed, had been finished. The gun was introduced in 1931 with double triggers.
Browning's son Val kept working on the single selective trigger design, which he finally perfected. It was incorporated as the standard Superposed trigger in 1939. This trigger uses an inertia block mechanism. It doesn't balk and it doesn't double. The Browning SST remains one of the very best and most reliable such triggers ever designed.
The barrel selector is incorporated in the sliding tang safety. Move the safety slider to the right to shoot the under barrel first, or to the left to shoot the over barrel first. Once a barrel is selected with the safety in the rearward (safe) position, the slider need only be moved straight forward to the "fire" position when it's time to shoot.
Like its single selective trigger, the Superposed's selective ejectors work first time, every time. They positively eject fired cases from the gun, while merely raising unfired shells for easy hand removal.
The action is held closed by an under-bolt that engages bites in the tandem lumps beneath the lower barrel. (The barrels are struck full length and the lumps are machined integrally with the lower barrel.) This system allows a "clean" breech face without protrusions to interfere with loading.
The takedown system of the Superposed is unique. A pull down latch frees the forend to slide forward, after which the top lever is used to open the gun and the barrels are simply lifted from the hinge pin. The latter can be replaced should it ever become worn. When the gun is taken down the forend stays attached to the barrels. This allows a tighter forend to barrels fit and also eliminates the possibility of misplacing the forend.
Superposed guns are not known for being especially lightweight, although special lightweight models (usually with straight hand stocks) have been produced. Nor, because of their under lump and bolt, are they shallow frame guns. But they are very solid, durable and handsome. They balance well and their mass helps to attenuate recoil.
The appearance and finish of Superposed shotguns has always been excellent. The receiver and barrels are highly polished and deeply blued. All Superposed guns are hand engraved and the engraving on the high grade models can be very lavish. The select French Walnut stocks gleam in hand rubbed splendor. To my eye the Lightning models with their Prince of Wales semi-pistol grip stocks and thinner forends are the best looking of the Superposed guns, but other configurations are available.