magnum12, this HMA is so large and varied, you'd have to be more specific as far as what portion of the HMA (which ranch, the species/dates that you're looking at hunting, etc.) and you may get some better information. We've hunted the southern portion of the HMA for antelope and the access that we've used has been through public access roads (county roads or BLM) or through a couple of surrounding ranches where we've got permission. Most of the parking areas will be accessible from some sort of public access road. You might get the BLM land status maps from the Casper office, most of the newer maps specify county/BLM/USFS public roads.