Thanks. Looking at Google AI it had this to say:
The Super-X / Super Speed Connection: Winchester introduced the Super-X brand in the 1920s as a high-velocity, hard-hitting game load. Pairing Super-X powder performance with Staynless non-corrosive priming made these shells immensely popular for waterfowl and upland hunting because they protected valuable shotgun bores.
The "Staynless" Innovation: Introduced by Winchester in the late 1920s and heavily marketed through the 1930s and 1940s, "Staynless" was the trademarked name for Winchester's non-corrosive, mercury-free priming compound. Before this, primers used chemicals that left behind corrosive salts, rusting shotgun barrels if they weren't cleaned immediately.
Well, all of the above from AI is wrong. The Super-X progressive burning smokeless powder, high velocity loads were introduced by the Olin's Western Cartridge Co. in their FIELD shell in 1922. The other companies quickly followed. Remington with their Heavy Duck Load which quickly morphed into the Nitro Express. Peters with their High Velocity. Winchester with various "Speed Loads" in both their REPEATER and LEADER shells.
Non-corrosive priming was introduced into rifle ammunition during the 1920s, but didn't get applied to shotgun shells until 1931/2, Western
Non-Corrosive, Remington
Kleanbore, Peters
Rustless and Winchester
Staynless. In December 1931 the Olin's bought the defunct Winchester Repeating Arms Co. out of receivership. Over the next few years Winchester's shotgun ammunition came to mirror Western's. Western Super-X = Winchester Super-Speed. Western's Xpert = Winchester's Ranger.
