Glitched: Pumpkin Patch
 

I have tried and tried to get this achievement. Multiple times I've gotten dual headshots; both by the way other people did it and the same way my friend got it. We have been playing it on the same XBOX, same file, and yet it won't pop up. Same problem happened with the Chapter 2 achievement, he got it right away but it popped up for me a day later. Pumpkin Patch has still not popped up, but I will keep trying.

Anybody have any suggestions?

Shotgun
 

I know this is late but I managed to get this with a shotgun. Not sure that'll help if it's actually glitched for you tho.

I've tried with a multitude of weapons, over and over again. It simply won't unlock. So far, it's the only one I've gone for that won't unlock. I'm still in need of half the kills for The Beast and need online capabilities for the online, but that one just won't unlock.