the canned, 11" CAR-15 easily-enough reaches 400 yd torsos, about 3/4 of the time. Since that's about twice the range that the .30 carbine, 30-30, 44 lever, AK clowns have, and since you NEVER DARE tell THEM that their choices are "too short ranged", you are just fos with your claims about the CAR-15.
A canned CAR MIGHT reach 400 yards 3/4s of the time IF you were a expert shot, IF you had a very good rest, and IF you KNEW it was 400 yards. The pos CAR has a pitiful trajectory, pitiful bullet weight, pitiful for 400 yard shooting.
Don't spend you time an a specialty weapon when this will be your ONLY rifle. At least a full sized AR-15! The Army ditched the CAR and the Carbine. That tells you something.