From going through my old ammunition catalogs it certainly seems the the specific Buck Shot offerings were in 10-, 12-, 16- and 20-gauge shells.
NITRO CLUB Buck Shot loads 1911-12.jpeg
ARROW Buck Shot Loads 1911-12.jpeg
From 1900 to 1909 UMC just mentioned a bit extra cost for Buck Shot loads. From 1910 through 1919 the Buck Shot loads were listed as the ones from the 1911-12 Rem - UMC catalog I show above. I suspect that the demand for 8-gauge Buck Shot loads was so small that they were never a catalog symbol item.
The only Winchester catalog of the period I have is 1916, and it's Buck Shot load offerings mirrors the Rem UMC Buck Shot offerings shown above. While Rem-UMC only cataloged 8-gauge loads with black or bulk smokeless powders, I see Winchester offered their 8-gauge LEADER shells loaded with dense smokeless powders as well.
Threaded Mode