Lag Issues

Can somebody help me figure out how to solve or reduce the lag issues I face in multiplayer games. Issues like:
A) I’m getting SEVERAL square headshots on a player with no shields left and he won’t go down which is easily confirmed in theater videos.
B) Opponent is hitting the airspace around me with perfection and is rewarded with a headshot kill also confirmed in theater videos.

I’d really appreciate the fileshare feature to post these amazing videos. I hope the sarcasm is helpful at 6:30am posting on this ridiculous topic #firstworldproblems. I have a 40mb down, 3 up connection and I don’t have this problem AT ALL in COD. My NAT is open and my network status is green.