I have two German double flint rifles, a SxS and an O&U, two barrels, two lock. Both about 1770 and about .65. European swivel breech double rifles show up from time to time - they did not originate in America - and in fact the Austrians had a swivel breech FL military musket, I don't recall right now whether both barrels were rifled or only one. Contrary to what one of the posts stated, double FL shotguns were used for flying birds and Joseph Manton was famous for making upland bird double flinters. A Manton double FL would be an interesting bird gun even now, they are beautifully balanced. The Brits made double FL rifles too but far fewer of them than the Germans ... but the Brits were not much as rifle shooters anyway until they began to get into India and Africa.