Bullet Penetration of Walls

Some information I've found on this topic:

• "Masonry Walls That Resist Bullet Penetration" (PDF)--Clay Brick Association of Canada. This paper details the results of tests done by researchers with Canadian Masonry Research Institute, the University of Alberta, and the RMCP. The article describes the construction of the various test walls, the results, and offers some concluding remarks. From the latter:

The results of this project were somewhat unexpected. The ability of a .22 Long Rifle bullet to easily travel completely through the corner of a typically constructed vinyl sided house was as unforeseen as the clay and concrete brick walls stopping all but the bullet with the greatest velocity. Standard 13 mm or 19 mm stucco finishing does not significantly reduce life-threatening situations for people inside or outside a wall that is subjected to most centerfire bullet impacts. This danger increases with the velocity and energy of the bullet fired. A person struck by one of these projectiles would be at risk of serious bodily injury or death. Secondary projectiles (wood, lathe, stucco, etc.) produced by a bullet travelling through one of these walls would also present a risk to a person. Walls finished with either a clay brick, concrete brick, or Tindlestone veneer prevented all but the .50 Browning from completely penetrating the wall assembly. The ability of the both the high strength (70 MPa) and low strength (17.5 MPa) clay brick walls to prevent bullet penetration was very similar. However, the localized behaviour of high and low strength bricks was substantially different. Upon impact, the low strength brick was turned into powder in the localized region of the bullet impact. 

• Another research paper: "Exploring cross-laminated timber use for temporary military structures: Ballistic considerations"--Georgia Tech. This link takes you to a page describing the object of the research and a link to download the full paper (450 pp.).
• "UFC 4-023-07 Design To Resist Direct Fire Weapons Effects, With Change 1"--Whole Building Design Guide and Department of Defense. As above, this link takes you to a page describing the paper as well as a link to download the full paper (74 pp.)
• Of course, the barrier tests performed by the Box 'o Truth crew are very informative. 
• Olympic Arms has an article, "Real World .223 Testing", that discusses penetration of the .223/5.56.
• A sale brochure from a company called Kibo that makes prefab guard huts and security barriers, touting the various barrier penetration resistance of their products.
• "Safe Rooms and The Active Shooter Threat (Part III)"--CIS World Services. As the author describes, "Part Three of this article continues by exploring options and performance expectations for safe room barrier components." It also has a nice bibliography listing other sources.
• "Designing Bullet Resistant Protection Panel Systems: Capture More than the Imagination"--Continuing Education Center.