The 7.62×40mm WT (Wilson Tactical)[2] is based on the 7.62×40mm wildcat cartridge, the shoulder of the WT was moved .003" forward and the throat was made .001" larger to accommodate mass-production tolerances while staying within the tolerance of the original reloading die tooling of the 7.62×40mm.
[1] Wilson Combat states that heavier bullets can be used in a barrel with a 1-8" twist rate for subsonic loads.
However, since most feral hog hunting is performed at night, he did not like looking for proprietary brass cases after he had fired them and designed the 7.62×40mm around the inexpensive and readily available 5.56 NATO cartridge.
[1][3] (The 7.62×40mm WT is a cartridge designed by Kurt Buchert and brought to market by Wilson Combat. )
[11] US Machine Gun Armory in Utah has begun offering a conversion kit for the Mk 46/M249 in 7.62 WT.