I didn't make it!
Ever wonderd what happend to your grenade, no BOOM!! Well I did, and I'v bin paying attention to that fact.
Like all good magician's they disapear through the wall's,
Don't beleave me? Just look, you'll see it to. I can't tell you exactly where they do because there are a lot of places.
I also think that those are the places where you can look through the wall's. (just lean over)
And finally, when your right behind your enemy and shoot him at pointblank with your shotgun and don't hit him at all.
I hope that those bugg's will be fixed in the new patch.