Why isn't achievement for gears of war isn't working?

Question

i just got 102 kills with a grenade tag on ranked match and i didn't get the achievement.

Answer 1

yeah its stupid

Answer 2

maybe you need to get bioshock. that is how i got that achievement.

Answer 3

play cod4, panzy

Answer 4

Either a couple of things of happened:

1. Your on Annex, you dont get weapon kills on Annex.

2. You have to stay till the end !! you leave half-way through you loose everything you gained

~Nick