Sorry for being dumb guys but I'm having trouble getting my head around this. Are we talking about frangible .223 loads only or standard jacketed cartridges, because to me the latter will penetrate and keep on penetrating, 7" in balistic gelatin, I could throw it harder than that !. I've only just read a response someplace else that related the story of an AD from a Mini-14 in .223, the bullet went through 8 internal walls in an apartment block before stopping.... in a sleeping 12 year old girl killing her stone dead. Surely standard rounds in a .223 will cut through anything compared to handgun rounds, all of which are grossly underpowered in any terms (velocity, energy or penetration) by comparison to even a "lite" rifle round like the .223. Surely this cartridge is strictly for the outdoors, if only because of muzzle blast, but as stated prviously if we are talking frangible rounds made out of compressed cookie crumbs then OK, personally I prefer HPBT in heavier weights like 64 gr, they show up much better IMHO.
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Mike H