Great! And better late than never.
As mentioned why not just get an 18" or 18.5" barrel if you are wanting it for defense. Also, look around as sometimes you can find the +2 extensions for cheap. I got mine from my gun store for $20.
Eph6:12 For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.13Therefore put on the full armor of God