Might've just been by chance. Their car got swarmed pretty quickly because of the commotion that made.

And if I'm not mistaken that we pretty close to when the one walker was shooting his own gun so may be they kept getting pulled in different directions

I'll also point out that the structure of the fair had a lot of fences and obstacles, so that may have also slowed the swarm down enough for them. Had they waited a bit longer at the same spot then I'm sure the swarm would have been bigger.

 

I just thought of that why didn't the walkers swarm the shooting walker

 

I do not remember the camera pans back to show us what happens to the shooting walker after they show Rick's car run out of the perimeter.

 

It depends. They've used guns in the past and haven't encountered a swarm of walkers. When they have, they've made a point to show the source of it, like in Season 2 Atlanta horde that responded to Carl's gun shot.

What I have more trouble with is when a character gets surrounded by walkers in the open (like Rick a couple of weeks ago) and gets away unscathed. That I just can't accept as realistic.

 

I thought the same thing, the walkers didn't even wince at the sound of the bottles breaking when Michonne shot. And then you got the sound of a rifle shooting..all I can think of is that she shot from so far away the sound was hard for walkers to pinpoint in which direction it was coming from (a BS excuse though)

 

The sound of Michonne's roof shot would have likely echoed around bouncing off the fairground structures and the woodline, so the walkers may not have known which direction it came from, but they should have shown some of them at least stopping in their tracks at the sound of it, and maybe turning in another direction. And I think the idea with the gun walker is that the other walkers were more stimulated by this moving car with a person pushing it than they were the gunshots. but I agree they should have shown at least a couple of them turning and walking towards the gun walker.

 

I agree that it seems the zombies don't seem to be a threat anymore. I get that the characters have learned how to deal with them, but still...when Rick and Michonne are busy counting them, as if to see who will slaughter the most walkers...it takes away the real threat the walkers pose.