It's not illegal if you are at or enroute to your hunting location. "But I use it for hunting" would not be a legal excuse for sticking it on your belt or in your backpack and walking around town with it.
Sec. 46.02. UNLAWFUL CARRYING WEAPONS. (a) A person commits an offense if the person intentionally, knowingly, or recklessly carries on or about his or her person a handgun, illegal knife, or club if the person is not:
(1) on the person's own premises or premises under the person's control; or
(2) inside of or directly en route to a motor vehicle or watercraft that is owned by the person or under the person's control.
(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; or
(2) the person is:
(A) engaged in criminal activity, other than a Class C misdemeanor that is a violation of a law or ordinance regulating traffic or boating;
(B) prohibited by law from possessing a firearm; or
(C) a member of a criminal street gang, as defined by Section 71.01.
(a-2) For purposes of this section, "premises" includes real property and a recreational vehicle that is being used as living quarters, regardless of whether that use is temporary or permanent. In this subsection, "recreational vehicle" means a motor vehicle primarily designed as temporary living quarters or a vehicle that contains temporary living quarters and is designed to be towed by a motor vehicle. The term includes a travel trailer, camping trailer, truck camper, motor home, and horse trailer with living quarters.
(a-3) For purposes of this section, "watercraft" means any boat, motorboat, vessel, or personal watercraft, other than a seaplane on water, used or capable of being used for transportation on water.
(b) Except as provided by Subsection (c), an offense under this section is a Class A misdemeanor.
(c) An offense under this section is a felony of the third degree if the offense is committed on any premises licensed or issued a permit by this state for the sale of alcoholic beverages.
Sec. 46.15. NONAPPLICABILITY.
(b) Section 46.02 does not apply to a person who:
(3) is engaging in lawful hunting, fishing, or other sporting activity on the immediate premises where the activity is conducted, or is en route between the premises and the actor's residence, motor vehicle, or watercraft, if the weapon is a type commonly used in the activity;