I think the use of an AR15 pistol would depend on the skill level of the person employing the firearm. I've shot AR pistols and personally do not like them at all. Even when using a single point sling and pushing out, I find it uncomfortable to use or get decent follow up shots. I also do not see the advantage of using a firearm that requires two hands to use effectively in a close residential quarters situation. I'd rather use my 9mm pistol knowing I can get effective and repeatable hits on target using one hand or two. I also prefer using a traditional pistol because I can have one hand free to operate a telephone, a flash light, open doors, grab/herd family into the fall back room. IMO, if you're concerned about over penetration buy some good defensive frangible rounds.

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-John