Now I didn't get this perk till after the the 1.4 patch so I don't know if anybody had this problem before the patch, but the bullet trails do not always appear, especially if 2 or more people shoot at you. I was on the DLC maps for most of the night and was pissed it did not highlight the bullet as it should all the time. All the other warnings worked fine.
But I did notice when we finally got a team to pick Penn Depot to play Team Possession all the trails worked just fine. but when again we picked a DLC map it didn't work all the time. Please fix as this is a very hard perk to get if you don't have friends to help you, and for it not to work as intended is really aggravating.
Side note: For those who may post and say this is a noob perk; say what you want, but to me it's 100 times better then proximity alarm because their is no pulsing sound that can make you paranoid and it just enhances the direction on which the bullets are coming from. To me there is only one true noob perk and that's AA. I know some will say low profile is one also, and it can piss me off when a whole team or majority of the team has it because it's a waste of peoples radar, something I have to work to get. It's not hard work, but it does render it useless. But it is something IMHO I can deal with because somewhere along the line I will run into you anyway and kill you with radar on or not.
But AA on the other hand is a free enhancement that protects you even form the first shot, which those who do not use it have to choose to either run with armor all the time (which slows you down) or run in and out of armor turning it on at the right time; which to me is a skill you learn after playing the game for a while and learning how people play the game.