In regard to #1 penetration, here are some excerpts from a lengthy article about home defense shotgun ammo.

This 12 inch minimum penetration performance guideline is meant to ensure that the bullet has adequate penetration potential to reach and disrupt vital organs. The 12 inch standard is the prevailing barometer used by the F.B.I.

[I]The Firearms Tactical Institute reports:

"Number 1 buck is the smallest diameter shot that reliably and consistently penetrates more than 12 inches of standard ordnance gelatin when fired at typical shotgun engagement distances. A standard 2 ¾-inch 12 gauge shotshell contains 16 pellets of #1 buck. The total combined cross sectional area of the 16 pellets is 1.13 square inches. Compared to the total combined cross sectional area of the nine pellets in a standard #00 (double-aught) buck shotshell (0.77 square inches), the # 1 buck shotshell has the capacity to produce over 30 percent more potentially effective wound trauma. In all shotshell loads, number 1 buckshot produces more potentially effective wound trauma than either #00 or #000 buck. In addition, number 1 buck is less likely to over-penetrate and exit an attacker's body."


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Home Defense Shotgun Ammo