Okay this is very strange...I thought that the achievement was broken...But it isn't...I tried 2 times at the second breaker where i shot 130-140 normal crawlers attempting getting this achievement and no luck...Then i thought what the hell i'm gonna try the place in the tunnels Steppenwolf referes to...And boom after i guess shooting 50 normal crawlers and baby crawlers i got the achievement...My conclusion is...For some reason or another the achievement won't pop at the place in the second breaker...Do the achievement in the place in the tunnels...It worked for me!

Your picture looks like where I just got mine, hive near a door that leads to the shotgun/save/craft area.. but the elevator on mine at least didn't say level 4. I imagine there's a few areas similar that are good for this achiev. though :) Good advice all the same.

Good ideas Steppenwolf and Gorlom[Swe], I was going to get back into this game and try to finish it off. Thanks for the helpful inputs! :)

I found a spot near the second breaker. at the top of the map near a door to another area there is a hive close to an obstruction. The spawned scavanger can't get past the obstruction even if they jump. all you have to do is stand on top of the obstruction and shoot it with your pistol.

Danke!

Thanks for this, I was wondering why mine didn't pop. Very helpful indeed.