LBJ National Grasslands has a nifty website.
The site has the following information about firearms:
Are firearms allowed?
Use, possession or transportation of firearms, bow & arrows and other arms or ammunition are allowed during designated hunting seasons. While possessing a firearm for the purpose of hunting you must have a valid state hunting license in your possession for the species you intend to hunt. The firearm possessed must be of the type legal for hunting the species that are in season. Notice: Any prohibited acts and other public hunting regulations do not in any way restrict a person having a concealed handgun license from possessing a concealed handgun, loaded or unloaded, on public hunting lands in strict accordance with the concealed handgun laws. For further information concerning firearms in Wildlife Management Areas refer to the "Prohibited Acts" found in the Texas Parks and Wildlife Public Hunting Lands Map Booklet.