Zombie Survival - Choice of Firearm

[ManiacallyChallenged]

I'm thinking about using a kneeling bus as a portable wall. If you drop it on it's tires there's only an inch or two left between the chassis and the ground.
One of the two segment bus dealies could be parked across a road, and people could fire out of the windows high on the side, which open so you can look down or straight out(not up).