Why haven't we heard of...

[OkieCruffler]

Nothing new, but you'll see it again, maybe not in the wheelguns tho'. I'm betting the encore shooters will start wildcating the 500 and 460 pretty quick. Alot of those necked down cartridges are a success, if not commercial at least ballistically. The 357/44 B&D is a pretty impressive cartridge, and the 256win mag is a great little close range varmit round. Sometimes those wildcats catch on to the general public, ie 22-250, 7-08.

 

[VUPDblue]

As to why, why not? It could be fun. We could take an example from the 7.62 x 25mm and load a 7.62 bullet in .50 caliber sabot and see if it works. Then we'd have the 7.62 x OhMyGawd

Been done. .50 S.L.A.P (Saboted Light Armor Piercing). 200gr. .30cal saboted into a .50BMG case. Military used these for a bit, but I think they are no longer utilized.
I load .223 bullets into a sabot and seat them into a .308 case. This makes for a great varmint round. Accuracy is not phenomenal, but I can get it to 2-3 inches at 125yds. But the speed is devastating. Something on the order of 4,000 fps or a touch less. ss109's saboted into a .308 could defeat some of the lighter vehicle armor, I would suspect.