In texas what happens if you shoot a home invader with a illegal Gun?

no charge for the shooting , but a charge for an illegal weapon

If the home invader is black, they throw you a ticker tape parade.

Personally, you would be a hero. Legally, you might be fined and/or told to register the gun.

There is NO SUCH THING as an illegal gun in Texas. If you are legally banned from having a gun, you will be charged for that.