Master Xanthan
Smash Champion
I got the sentry gun kill easy. All you need to do is set the Sentry Gun as one of your killstreaks. Play in free for all, get the sentry gun killstreak, call in the crate, hide and let an enemy take it. Then knife the sentry gun when the enemy brings it out(also put on hacker so it will be easier to see it in case you die).