There is a lot going on in your question. Assuming that the base charge is a Penal Code 246, shooting at an inhabited dwelling, the sentencing range would be 3 years-5years-7years, and this is a strike. A gang enhancement under Penal Code 186.22(b)(4)(B) added to that charge carries a very severe penalty of 15 years to life in prison. You mentioned the "use a gun and you're done" law, and under Penal Code Section 12022.53, there are a variety of enhancements which could apply to at PC246, but not to a PC245(a)(2), which apply for the use of a firearm, discharge of a firearm, and causing great bodily injury or death. This is the type of case which is very fact specific and I recommend consulting with an attorney who has experience with gang cases and firearm enhancements. I know from experience that these cases require much preparation to effectively defend.