Kent Cartridge manufactures shells in Kearneysville, WV and as such follows SAAMI standards in reporting velocity as 3 feet from the muzzle.
Gamebore manufactures shells in England, and as such follows CIP standards, which report significantly higher velocity.
Scroll toward the bottom here
https://www.shotgunworld.com/bbs/vie...63546&start=20
One example
Eley VIP Game 32 gram plastic wad #6 shot UK website = 410mtps (1345 fps)
Eley VIP Game 32 gram plastic wad #6 shot SAAMI tested = 1222 fps