In Call of Duty 4: Modern Warfare, the creators have introduced a new Bullet Penetration system to both Single-player and Multiplayer that allows you to shoot through certain objects in the game that would normally be used as cover (i.e. Walls, floors, ceilings).
What you can shoot through depends on three main variables:
* The Ballistics of the weapon you’re using.
* The relative ‘thickness’ of the object you’re shooting through.
* The distance between you and the object you’re firing into.
These three things determine IF you can shoot through the object, and if you can, how strong the bullet will be once it passes through it.
It changes the entire way you play the game; suddenly it’s not just about getting to cover, but about getting to hard cover. In multiplayer, this can change your tactics dramatically. Rather than simply picking a weapon to take into a firefight, you can carefully craft your weapon’s load out to the environment you’ll be fighting in.
In the video, they made sure to take huge advantage of bullet penetration, showing off how the M249 SAW makes light work of thin plaster walls and wooden floor boards. Now how does the Deep Impact perk play into this?
for a weapon like the M249 Saw (featured in the video), obviously it has the power to easily shoot through plaster walls, wooden floors, and even some fairly thick stone walls--but what about an M4 Carbine, or some other lower caliber rifle? Normally, weapons like these wouldn’t be able to penetrate stone walls or thick surfaces like the M249 SAW.
However, if you have Deep Impact selected as a perk, you will have INCREASED bullet penetration on whatever weapon you use. This allows you to pierce thicker objects, and with increased strength as it passes through. Turn Deeper Impact on and your M4 Carbine that used to be stopped by thin walls now penetrates through them easily, taking out anyone attempting to use it as cover.
Keep in mind though; you are limited to only three perks per custom class. So in order to have Deep Impact, you’re giving up something else, such as LAST STAND, or another perk.