I use the hand cannon as many primary weapon in most modes (excluding the crucible) and one thing I've noticed is that when you're coming down from a double jump (like jumping over a shipping container, or a boulder, anything where you're descending down from a higher elevation to attack an enemy) while ADS on an enemy to perform a headshot the shot never registers. It's as if I never shot a bullet. Even if I aim for center mass it never results in a hit marker. Now, it could very well be my lack of time with the game to get my timing just right, I fully understand that. But I've tried this attack dozens of times and I have yet to perform a headshot. To be fair, the throwing knife works like a champ! I've jumped off ledges and over obstacles and had some highlight worthy kills with it. I'm loving that! But for whatever reason, the ADS headshot while coming down from higher elevation isn't working for "me". If anyone has perfected this technique and has better results, I'm all ears. So far I'm loving the game. Even with the little time I've had with it it's been a great experience and can't wait till September. Updated: I played the beta on my 360 as well and I was a Warlock and had the same issue. Not once did I get a headshot.