My bad I found this in a PDF on the DFW website...
What about target shooting, “plinking”, or firearms for personal protection?
The Commission does not regulate these activities. Use of lead projectiles is legal unless another government entity has determined otherwise for lands they administer. The regulations prohibiting lead only relate to possession while engaged in specified hunting activities.
So as long as you are not hunting you can use lead rounds, if you are hunting big game in the area you can not use lead or have lead rounds for the weapon you are using to hunt big game.