In order to unlock this, all players on the (winning) team must have their Snub pistols out by the time the scorecard splash screen comes up at the end of a round. Since you need four other people to do this right so the achievement can pop, you can do it on your own with a second controller in a Private Versus match faster and easier.
Sign in a guest account and go to the Private Versus menu. Pick a map, preferably a small one such as Raven Down and set the game mode to Warzone. When the match starts, pick up an explosive, preferably frag grenades. Go to your guest and throw one grenade at them. Before it goes off and kills the guest, switch to the Snub and look to the sky for added dramatic effect! The achievement will pop almost immediately.https://xboxdvr.com/gamer/anima-pura/video/63386864
P.S. The game doesn't seem to be able to record your right stick movement, so looking to the sky with the Snub equipped doesn't seem to differ from just having it out at the end of the round.