Hello, I see the discussion going on about bolting systems. What would be the name of the bolting system used on the Remington 1900. I can find no information about it or what it is called. The top lever seems to cam the rib extension down into place as the top spindle returns to center. My 1900 top lever is well left of center, but still locks up very tightly. It seems a very robust design. Thank you

The bolting on Remington Hammerless Double Barrel Shotguns started out as Purdey double underbolts with a third fastener, in the Remington case the rib extension, middle barrels in the picture --



These early guns were named "bridge frame" guns by Charles Semmer who wrote the book on Remington Doubles --



A few years into production they simplified their frame milling by eliminating the "bridge" and used two small tabs on the foreward part of the bolt engaging notches on the sides of the barrel lug, rear barrels in the picture above --



By very late Model 1900 production they eliminated the foreward tabs on the bolt and the milling of the barrel lug and just used a single underbolt and the rib extension, front barrels in the top picture.