One of the coolest new features about Modern Warfare 2 is the wide variety of weapon attachments that are available to players. One of the newer weapon attachments to the series is the Full Metal Jacket, or FMJ for short, which is similar to the Deep Impact perk from the previous Modern Warfare. FMJ is probably the most often chosen weapon attachment, because like Stopping Power, many players believe that FMJ does more than it actually can. In reality, FMJ is only able to reduce the amount of damage lost per bullet when a player is shooting through some kind of material. These materials include but are not limited to walls, windows, grated floors, and even an enemy’s teammate. Let it be known that FMJ has no effect on the bullet damage done to an enemy who is out in the open. When fired, FMJ bullets usually appear with a glowing bright red tint around them, which actually looks pretty legit and is one of the better features about this attachment.
One thing that is somewhat of a nuisance about this attachment is that in order to gain the Extended Mags attachment for most of the weapons, players must get 40 bullet penetration kills, which for most players is a bit of a stretch. Overall, in my opinion FMJ is next to useless on the weapon attachment pyramid. I would only recommend using this attachment if you had no other options available or if you wanted to score the Extended Mags attachment. To close, I have killed and been killed through several different objects while playing multiplayer and in both cases the FMJ attachment was not equipped. By this I mean, the amount of penetration a bullet can have is still pretty large without FMJ, so put your weapon attachment options to better use and try not to, if at all use FMJ.
Below is a video giving a few tips on how to get 40 FMJ kills pretty fast.