Given the widespread availability of this information for over a decade, I am shockingly surprised to read about the "overpenetration" with "high powered assault rifles". In this day and age anyone who is spouting this BS needs to be horsewhipped... Several respected organizations have done structural wall testing, including the FBI, CHP, and IWBA. In our IWBA and CHP testing, replicas of standard construction interior walls were fabricated using two pieces of 1/2” thick dry wall cut in 12” x 24” segments and mounted four inches apart using 2 x 4” fir studs and 1.5” dry wall screws. Five rounds of each load were first fired into bare gelatin to serve as controls. Then 5 shots of each load were shot through interior wall segments into gelatin blocks placed a set distance behind the intermediate barriers--various distances have been tested, typically ranging from 1 to 10 feet.
Generally, common service caliber JHP bullets failed to expand and had very deep, excessive penetration after passing through the interior wall, due to plugging of the hollow point. With the hollow point plugged, the bullets performed nearly identically to FMJ pistol bullets. The terminal performance of the 12 ga. 00 buckshot and slugs was not altered by passing through interior wall replicas, with penetration and deformation nearly identical with their performance in bare gelatin. Likewise, .308 rounds were not usually effected by the presence of an interior wall intermediate barrier.
With one exception, the majority of the 5.56 mm/.223 loads, including M855 62 gr "green-tip" FMJ, which were fired through interior walls demonstrated either minimal changes in terminal performance compared with bare gelatin or reduced penetration. The major exception were 55 gr M193 style FMJ projectiles which exhibited minimal fragmentation and deformation after first passing through interior wall replicas and hence penetrated deeper than in bare gel. Since all of the 5.56 mm/.223 bullets fired through the interior wall had significantly less penetration than 9 mm, .40 S&W, .45 ACP, and 12 ga. shotgun projectiles which were fired through an interior wall, stray 5.56 mm/.223 bullets seem to offer a reduced risk of injuring innocent bystanders and an inherent reduced risk of civil litigation in situations where bullets miss their intended target and enter or exit structures. As such, 5.56mm/.223 caliber weapons may be safer to use in CQB situations and crowded urban environments than service caliber handguns or 12 ga. weapons.
Obviously, it is important to keep in mind that purpose built barrier blind 5.56 mm/.223 projectiles, such as the 55 & 62 gr Federal Tactical JSP’s and the Nosler 60 gr Partition, will offer deeper penetration than fragmenting designs and may exit.
