In the first years of the 20th Century Union Metallic Cartridge Co. had two high brass shells, TRAP with the flat base wad for bulk smokeless powders and ARROW with a high base wad for dense smokeless powders. For 1905 UMC began offering an ARROW shell for bulk smokeless, but the 8-gauge loads were still in the TRAP shell --
TRAP 8-gauge, bulk smokeless powder,1905.png
The EXPERT was the NPE equivalent to the loaded TRAP shell --
8-gauge EXPERT shell.png
By the 1907 UMC catalog the TRAP shell is gone. While the TRAP shell is in the 1906 catalog, the pages are X'ed out in the copy I have access to.
Threaded Mode