The Heavy Express range of cartridges was developed by Jim Busha, from Colorado Springs CO, and was based on the 348 Winchester case with the rim removed. They came in a variety of calibers, ranging from .240 to .500 caliber and in 2 different versions, namely the “normal” length (Heavy Express) and the shorter length (Heavy Express Short Action Magnum). These can almost be argued to the forerunners of the Winchester Short Mag and Winchester Super Short cartridges.

Source: Internet