Lagopus,
BSA also made the BSA Single Xii, using a William Baker action. The same Baker who invented the ejector and the Lancaster 12/20 action. The Single 12 is nothing like the Snipe. The all steel action is a work of genius, using just one coil spring to power the tumbler, the trigger, and provide auto rebound. It probably can be customised to be a superb single. But, it is a "semi hammerless" ie hammer gun which is out of the original posting specs.
If anyone comes across a BSA Single XII, grab it.
