TexasCHLforum.com

Texas Penal Code Chapter 46 section 46.01 says:

Short-barrel firearm" means a rifle with a
barrel length of less than 16 inches or a shotgun with a barrel
length of less than 18 inches, or any weapon made from a shotgun or
rifle if, as altered, it has an overall length of less than 26
inches.


The barrel is measured from the face of the closed bolt to the muzzle. I do not think they include muzzle breaks or flash suppressors as part of the barrel. The feds may have a different definition, but I think the barrel length matches.