Does anybody really want a guide on this because it is quite simple like if you search bf3 wiki for a gun it will show its ammo type such as 5.56x45 NATO thats rounds for m16a3 and if you go into this and click on Weapons>Common>Bullets>5.56x45 NATO you will find something called Bullet entity Data, in that there will be a start damage and end damage set these to like 200+ doesnt really matter it will be a instant kill. Once you do that there is some other things that say like falloffdelay damage and blah blah just change them to 200 or more and go to file>save and activate selected cat. Then go ingame and Poof you have instant kill bullets for that bullet type. :) hoped this help and if anybody really needs it i might make a video just tell me