Just a little note, if you have ghost equipped and you destroy a sentry gun in any way, shape, or form, it counts towards the pro perk. I just destroyed a sentry gun with my Chopper Gunner and completed the challenge.
I'm assuming it also works for mortar strikes, rolling thunder, gunships, and napalm strikes as well. --- LIVE is still the internet. And people are ass hats on the internet because you can't punch them in the face for it
It's not just a sentry gun, it's a turret kill so you can destroy a SAM turret as well. What I do is I buy the sam turret and throw it into the enemy spawn. They usually put it back there and I just go back for it and knife it.
I'm pretty sure it's just a sentry gun. The challenge does say "Destroy Sentry Gun" and I'm also pretty certain I've taken out plenty of SAM turrets and didn't get the challenge. --- LIVE is still the internet. And people are ass hats on the internet because you can't punch them in the face for it