“A 12 gauge with 00 buck would be a far more effective tool.”
Not against 20 plus people.
If you take out 2 or more, you've won the battle with a superior kill ratio.
My Mossberg holds 5 shells. The first shell goes into the ground. The next one is aimed at the guys coming towards me. If that doesn’t discourage the rest of the group, the remaining 3 shots will ensure that their number is much diminished before they get to me.
That said, gang members are by definition COWARDS, and will always scatter and run away when they are faced with a determined defense.