Anyone else not able to get the achievement Hella Copter?

[BLVCK MVGIC]

I am unable to do damage to the military attack chopper. I am level 50 and had a full stock of machine guns. I sat on the roof over the picnic tables, and burned through all my guns and I could not destroy it.

I am using variable framerate. idk if that has ties to the engine or damage counter or range where bullets do damage. I tried switching to 30 and 60fps but that didn't help either.


EDIT/UPDATE: I restarted my game and tried one more time. I was successfully able to shoot down the chopper. I tested out some shots on far away zombies and walls to discover that there is a bit of bullet travel time. So I just lead my shots a bit more with each pass.

https://www.youtube.com/watch?v=_gpaX0_PTMU

[Nevander]

I had the same problem. I thought I was hitting it and usually it would go down MUCH quicker. Eventually after four machine guns I managed to take it down.