As far as I can tell, the basic problem is not wasting ammo, and using fire to drive the zombies, the way our ancestors drove animals off cliffs. I mean, the guard armories have some. The military armories have some. But you don’t wanna waste it with suppressing fire. You wanna use fire to drive.
There is a reason we will never have a full blown zombie apocalypse. We are too good at killing. There is a reason we can reverse a zombie apocalypse. Those are the same reasons. We are just too good at killing.
Use maneuver. Don’t waste ammo. Use fire to drive. Then be efficient with it. Street to Street. House to house. Fire. Shoot. Move. Take all the foot, water, gasoline with you as you move.
Zombies will eat each other. Remember, three days without food and every zombie will develop Rage.