The standard 308 is 147 grains while this round is 180 grains so no it is not a lighter bullet. You are right this is a great rifle and cartridge design, but that is what is needed to bring this all together. The reason I posted this video and not one off youtube is these are the people that make these rounds. Look on the website they tell you the f/s. And it being sub sonic you should already know its less then 1050 f/s. As most subsonic ammo is. All this aside without sub sonic ammo all you hear is the sonic boom the round makes not the report of the rifle making it so a sniper in a good hide can stay hidden with the enemy having no idea where the shooter is. With that also being said there is no reason that in COD4 that you can not have a silenced sniper rifle where you hear the shoot but the snipers location does not show up on the UAV
