I found the articles on penetration comparison interesting reads. However, the only .223 ammo tested was Mil-spec Ball, and 55gr Varmint hollow points, neither of which are designed to penetrate in SIMULATED tissue. Actually they performed quite as I would have expected from 24yrs of law enforcement experience of which 21.5 have been as a conservation officer and witnessing or inspecting gun shot wounds on various species to include Homo sapiens.
I don't have much "laboratory" testing experience, but I do know this.....
Except with FMJ-AP, the 9mm can't be expected to penetrate a L-III Kevlar vest, however the .223 will !!!
With ammunition such as 55gr or heavier soft point, the .223 is vastly a better stopper on human sized targets with fur coats on..... ie: Whitetail deer.
I have shot in excess of 20 deer with .223, make that over 50 to include the .22 Hornet.
I have shot in excess of 30 with .355-.358" diameter pistol cartridges, and that dosen't count the car-collision "put-downs", usually accomplished with .22rf or .38 semi or full wadcutters.
Conclusion: Penetration is much more dependant on bullet style and construction than caliber (diameter in tenths of an inch).
A 9mm or .357mag (or .35 Remington that that matter), loaded with a 90gr Hollow point (say the 90gr Sierra Hollow cavity) for instance, will penetrate FAR less than a 60gr Nosler Part. or 63gr Sierra, or 70gr Speer Soft point from a .223
Conversly, a Steel jacketed WWII surplus 9mm ball "SMG" round will FAR out penetrate a 35gr Hornady V-max from a .22 CF on "soft" targets such as ballistic gel.
Comparison of the two (9mm vs. .223) quickly becomes an Apples to Oranges comparison.
BTW: I still prefer the Marlin Camp Carbine to "Storm"
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