Final Headshot?

Am I the only person who seems to consistently miss the 5th headshot with DMR/BR? I’m not talking about accuracy, my reticle is red and centered on the forehead but the shot won’t take them down. A bad habit I carry over from H2 was instant reload once you killed a player and I find myself often reloading when I thought the enemy would be killed but the last headshot didn’t do anything? Its not the connection, I’m not lagging. It happens consistently in all game types and maps and doesn’t make any sense. When H4 first released, I didn’t notice this happening. Also when a player was running to escape fire, you could still take him down with a single headshot in the back of the head if he had no shield. Now it seems like it takes 3,4,5 shots to kill an enemy from behind AFTER his shield has already been raked off? Has something changed?