why settle for having 400 ft lbs of energy with which to stop an attacker,when you have 800 ft lbs? Why be without the 300m "reach", the penetration advantage,etc of the 223? A 10" barreled 223, with an 8" long sound suppressor,is every bit as handy as is a .30 Carbine, and a helluva lot of 'room clearing" was done with the carbine, in ww2. Probably more than has been done since, by any rifle ever fielded,actually.