why cant ya have both? If I am on American Soil give me my AR, if i am over seas give me the AK , all comes down to what ammo you can get in a hurry
You can almost have both....buy an AK in .223
No, the .223 doesn't have the same "knock-down power of the 7.62x39, but that was not in the design parameters of that round. We were looking for something that was "lighter", hence more load carrying capacity (rounds) for the infantry man carrying that weapon.
As for penetration, the theory was that the round would penetrate then bounce around in the body, causing possibly fatal wounds, or enough of one to incapacitate that person, causing possibly the loss of service of a few of his comrades as they tended to their wounded or carried them out. This was all in the original theory, not always practiced in the field, as they often left their wounded behind if need be.
The AK is by far the most reliable design in a combat weapon and has been since the 1940's. No, it isn't as accurate as an AR can be, but it wasn't designed for that. It was designed to deliver lead, and does so very well. In the hands of someone that is experienced with it, and within the range it was intended to be used at, it is as lethal as anything out there. The AK's in 5.45x39 can be as light as alot of AR's, specially with poly stocks on them.
The AR, again, is more accurate, requires more maintenance, but is far more FLEXIBLE. You can easily modify an AR to fit most needs. Stocks and pistol grips, rail systems, trigger groups, etc. are easily changed, allowing you to add accessories like optics, lasers, vertical grips, flare launchers, etc. You can even buy or assemble different uppers that can be swapped back and forth on one lower receiver to fit the need again, whether it be Tactical and short for convenience, or a long range/target/varmint upper for reaching out and touching something. This is something that is not easily done on any AK.
There are many other differences, pros/cons, it's all in what fits your needs best.