Oh, no. There's no comparison with regard to over-penetration. The 5.56 has more than twice the muzzle velocity of the .45ACP, with 2200fps vs 875fps (5"-6" barrels). Out of longer barrels, the difference becomes even greater. .45 may have more knockdown power at short range, but 5.56 is a very hot round that easily penetrates through flesh and walls and just keeps going. Effective range of the .45 is about 100-150yds, and 5.56 is about 500yds.