It's a good thing they won't need a high capacity magazine for that.
For Iraq & Afghanistan, the US fired an estimated 250,000 for every insurgent killed. These are trained military.
Based on that if DHS were the trained equivalent with 670M rounds they’d be able to take out 2680 people.
Remember there’s 300M plus guns in America owned by approx 88M people. If just 2% get pissed, that’s 1.76M armed people with 3.4 guns each.