So long as you within the parimeters of the federal laws and follow the state and local guide lines that are required you can file for a Class 3 to get a sub machine gun so long as they are legally registered.
House Amendment 777 to H.R. 4332 to ban the civilian ownership or transfer of any fully-automatic weapon which was not registered by May 19, 1986. However, any such weapon manufactured and registered before the May 19 cutoff could still be legally owned and transferred by civilians.
You cannot own one if you are guilty of any of the following
■Anyone who has been convicted in any court of, a felony punishable by imprisonment for a term exceeding 1 year, excluding those crimes punishable by imprisonment related to the regulation of business practices.
■Anyone who is a fugitive from justice.
■Anyone who is an unlawful user of or addicted to any controlled substance.
■Anyone who has been adjudicated as a mental defective or has been committed to a mental institution.
■Any alien illegally or unlawfully in the United States or an alien admitted to the United States under a nonimmigrant visa. The exception is if the nonimmigrant is in possession of a valid hunting license issued by a US state.
■Anyone who has been discharged from the Armed Forces under dishonorable conditions.
■Anyone who, having been a citizen of the United States, has renounced his or her citizenship.
■Anyone that is subject to a court order that restrains the person from harassing, stalking, or threatening an intimate partner or child of such intimate partner. (Added in 1996, with the Lautenberg Amendment.)
■Anyone who has been convicted of a misdemeanor crime of domestic violence. (Added in 1996, with the Lautenberg Amendment)[6]
■A person who is under indictment or information for a crime (misdemeanor) punishable by imprisonment for a term exceeding two years cannot lawfully receive a firearm. Such person may continue to lawfully possess firearms obtained prior to the indictment or information, and if cleared or acquitted can receive firearms without restriction.
as far as I know Texas does not have any restrictions on ownership of machine guns. But the misconception of you cant own a machine gun is a myth. (California laws may vary they are funny that way)