Generally speaking, Texas law allows people to transport a handgun in their vehicle as long as they are otherwise allowed to possess a firearm. Texas Penal Code Section 46.02 creates an offense for the unlawful carrying of handguns and in subsection (a)(2)(b), makes an exception to unlawful carry for those who are:
(B) inside of or directly en route to a motor vehicle or watercraft that is owned by the person or under the person's control.
Additionally, section (a-1) states that only those with a Texas License to Carry (LTC) are permitted to keep a handgun in “plain view” within the vehicle. Those with an LTC must keep their handgun in a shoulder or belt holster if their handgun is in plain view.
(a-1) A person commits an offense if the person intentionally, knowingly, or recklessly carries on or about his or her person a handgun in a motor vehicle or watercraft that is owned by the person or under the person's control at any time in which:
(1) the handgun is in plain view, unless the person is licensed to carry a handgun under Subchapter H, Chapter 411, Government Code, and the handgun is carried in a shoulder or belt holster; or
We have not found any Texas laws that restrict transporting a rifle or other long gun in a motor vehicle or watercraft. We have also not been able to locate a law that would dictate if a long gun can be "in plain view" in the vehicle.
It is important to keep in mind that other laws may prevent one from carrying a firearm at any time, or may restrict the location where firearms can be carried. For example, see section 46.04 of the Penal Code, Unlawful Possession of Firearm.