TX is right, the STATE law is 300 feet and 'only' enhances the penalty if you commit another offense. It does not prohibit carrying in a parkinglot, playground, or exterior walkway.
The federal law used to be 1500 ft was ruled unconstitutional in Lopez. However, congress said the constitution allows us to regulate interstate commerce, guns/gun parts/ammo is shipped interstate, we can regulate them and we create a 1000 foot gun free zone. However, if you read the law, sub-paragraph (q) exempts CHL's from said law (it does not protect your deer rifle or duck gun, only your pistol
)Hope this helps.