There appears to be significant confusion regarding the terminal effects of “frangible” ammunition and its efficacy for duty/self-defense use.
The first task is to define what exactly is meant by “frangible” ammunition. Frangible projectiles are specifically designed to break apart into small dust like particles when hitting hard structures--typically steel targets, and generally fall into two categories: training ammunition and Reduced Ricochet, Limited Penetration (RRLP or R2LP) loads. It is important to note that although frangible ammunition ideally disintegrates against a hard steel target, that does NOT mean it will break apart against/within less dense materials, including soft tissue.
Various types of frangible training ammunition have been available since WWII. Frangible training ammunition allows safe close-range training events when using steel targets, reduces the danger of wall penetration in indoor shoot houses using steel bullet traps, and can result in less airborne lead contamination, as most frangible projectiles do not contain lead. Frangible training ammunition is frequently not as functionally reliable or accurate as duty ammunition. In testing, 9mm 87gr Greenshield frangible ammunition with velocities of nearly 1600 f/s was able to fully perforate soft armor, but would completely shatter against 5 mm steel plate with no visible damage to the steel. It would chunk out a 3 inch deep divot when fired against a reinforced concrete wall, yet in tissue it acted like 9mm FMJ, with no deformation or fragmentation and 22-24 inches of penetration. Likewise, Federal .223 26 gr frangible training ammunition fragmented completely against steel, easily penetrated soft body armor, but in soft tissue created wounds of no greater severity than seen with a non-deforming .22 LR projectile.
Reduced Ricochet Limited Penetration loads are typically intended for CQB operations where significantly reduced ricochet and limited penetration potential around shipboard bulkheads or industrial pipes is necessary in order to reduce risk to innocent persons and friendly force personnel, as well as to reduce the risk of release of hazardous industrial and/or other dangerous materials. For example, for its intended niche role the Black Hills Mk255 Mod 0 5.56 mm 62 gr R2LP (AA17) ammunition offers good unobstructed soft tissue terminal performance on par with other military 5.56 mm loads, but is not ideal for general CQB or land warfare use do to difficulties defeating glass and other commonly encountered intermediate barriers.
RRLP ammunition may be of benefit for personnel conducting VBSS, GOPLAT, and in extremis missions in maritime environments or industrial settings with hazardous materials. Likewise, the use of frangible training ammunition is an important safety consideration for close range exercises using reactive steel targets. On the other hand, frangible training ammunition is NEVER a good choice for duty/self-defense use! Anyone recommending frangible training ammunition for duty/self-defense purposes is grossly misinformed or is ignorantly repeating specious gunrag myth and should be disregarded as a source of valid information…