@P!nk I have noticed that gun accuracy differs from map to map. On some maps I can use the ACR just fine, and other maps I will get unregistered hits like nobody's business. This also applies to AK47, Steyr and SCAR-H, maybe I am bad at aiming - I don't know. I have been trying to record but unsuccessful to get a decent movie of it. When using snipers, shooting from a vantage point while prone gives better accuracy than standing on level with the target - IMO.
You may also want to use the following commands, they seem to make a noticeable difference.
/cl_packetdup 2
/snaps 30
/cl_maxpackets 100 (I'm sure you knew already)
@Sammy I blew a car on Red-Barron at his feet and all I got was a helmet (armor). I shot 2 tubes at another guy and got the armor twice. I would think the first tube would weaken the armor and 2nd would give me a kill. Not sure if its a bug or even a real issue but it does get annoying. I was not using Stopping Power or Sonic Boom.