AK Corner: AR-15 vs AK-47 Wood, Concrete, and Steel penetration test Posted on 4 October 2024 by The Tactical Hermit AR-15 vs AK-47 Wood, Concrete, and Steel penetration test The 7.62×39 FMJ chews up most cover. One of the many benefits of having a big and slow .30 caliber round versus a light in the ass but fast .22 Calber round.