Local Government Code Chapter 229 is the statute that covers this. It stars with 229.002
Sec. 229.002. REGULATION OF DISCHARGE OF WEAPON. A municipality may not apply a regulation relating to the discharge of firearms or other weapons in the extraterritorial jurisdiction of the municipality or in an area annexed by the municipality after September 1, 1981, if the firearm or other weapon is:
(1) a shotgun, air rifle or pistol, BB gun, or bow and arrow discharged:
(A) on a tract of land of 10 acres or more and more than 150 feet from a residence or occupied building located on another property; and
(B) in a manner not reasonably expected to cause a projectile to cross the boundary of the tract; or
(2) a center fire or rim fire rifle or pistol of any caliber discharged:
(A) on a tract of land of 50 acres or more and more than 300 feet from a residence or occupied building located on another property; and
(B) in a manner not reasonably expected to cause a projectile to cross the boundary of the tract.
229.003 increase the restrictions for counties with larger population.
(a) This section applies only to a municipality located wholly or partly in a county:
(1) with a population of 750,000 or more;
(2) in which all or part of a municipality with a population of one million or more is located; and
(3) that is located adjacent to a county with a population of two million or more.
229.004 applies to a municipality located in a county in which the majority of the population of two or more municipalities with a population of 300,000 or more are located.
https://statutes.capitol.texas.gov/Docs ... LG.229.htm
235.022 allows the commissioners court to prohibit or otherwise regulate the discharge of firearms and air guns on lots that are 10 acres or smaller and are located in the unincorporated area of the county in a subdivision.
https://statutes.capitol.texas.gov/Docs ... tm#235.021
Subdivision has a specific meaning. It is any plat that is subdivided into lots for which infrastructure must be added, if I have 100 acres along a road that I can subdivide into lots without having to install new roads or utilities that is not a subdivision.
IANAL, this is my understanding.