Halo 3 achievement Headshot honcho problems..HelP?

[yaymakefriends]

I go on campaign then use the battle rifle or sniper and shoot 10 enemies in the head and i dont get achievement..What am i doing wrong?..Im not using skulls either

 

[VileHazerd]

You're probably going to have to try again. Play it on The Ark, where you get a Sniper Rifle right away, and try again. Don;t shoot unless you're sure it's a kill and play it on Normal.

 

[Adam B]

you can also get the achievement in a ranked free for all game on xbox live, but if you dont have that, thats probably why you are getting it in campaign, are you sure you are actually getting headshots? i mean, i'm not questioning your ability i'm just saying are you taking them out with a single shot, or does it take a few times, cause you may be nipping them in the shoulder without realizing it...using the sniper is the easiest way

 

[King ofda Cage]

The other answers are wrong. I'm sure you're shooting them in the head since it gives you a medal everytime you do. But xbox live has been having problems with achievments lately so that's probably why your not getting it. They also are having problems with getting armor perms.