You do have a point
What we did, when it looked like Rita would come to call right over our heads, was to LOAD UP on ammunition for the rifles, shotgun, and pistols. It would have taken several guns, but there were certainly well more than 50 rounds available. What we couldn't have done was do really rapid fire for a very sustained period (I guess with rapid fire, 30-60 seconds is "sustained") Of course, a mob of looters in a residential neighborhood is less likely than in a commercial area (there's a lot more of interest in downtown Houston than in suburban Harris county). What we WERE ready to do, was to take on up to five or six if need be.
Now that youngest son also has his .20 gauge, that would go up a bit.
(But I might get the AR15's for fun!)