I think you are confusing "00 buckshot" which is what is used in mw3 with "birdshot".  00 Buck shot is actually extremely lethal out to a good range.  00 buch shot in real life is 13 pellets with each pellet being a 33 caliber ball.  To put this in perspective the 9mm handgun round is only 35 caliber.  Now the 9mm round has rifling and more weight behind each round because of its elongated shape.  But a 9mm round is still lethal at 125+ yards.  00 buckshot because it isn't rifled will lose its energy quicker but not that quick.  It takes about 75 yards for buckshot to lose enough velocity to stop inflicting mortal wounds and start inflicting flesh wounds.  Buck shot is lethal to large animals out to 50+yards.  So 20-30 ft. is a chip shot for buckshot.  Bird shot is the one that is only lethal to like 15 yards.

In mw3 shotguns are very easy to beat.  The pumps and aa12 are anyway.  Rapid fire smgs with steady aim and qickdraw will absolutely decimate shotguns.  Shotguns are actually really bad in this game.  If that is your opinions on shotguns in mw3 then you have not used them.

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