Understanding the problems of the M16 in Vietnam, it was originally a propellent and cleaning problem. The AR-15 is a commercial derivative of the M16 and the the difference apart the powder burning speed for throwing the bolt back at the same time as throwing the projectile forward is the "key". It was felt in Vietnam the M16 did not have enough killing power, but it was accepted that it was effective on the Vietnamese whom were actually quite small in body build and the .223 was the smallest center-fire "high powered" rifle caliber. While pistols such as 44 and 357 magnum are a tactical comparator to the .223 , the killing power in civilian terms shows with what occurred by "John Holmes dark knight shooting". The wounding rate at close range is very high. The ammunition he used may not have been the military equivalent but it shows in the dark knight shootings by the high wounded survival rate on "human first world body form and health" ! Martin Bryant used the same weapon at Port Arthur but did that in lighting and had some coaching from military magazine(text) articles it is considered, and fired at the head point blank when in the cafe. In understanding rightful home defense(USA), an AR-15 with a 10 round magazine and the cheaper less powerful propellant is an ideal when you understand a 9mm pistol or 45ACP is very ineffective "erratic" knock down power and will have the same behavior as the AR-15 at kill and wounding at close range. If the magazine capacity for semi auto rifles were agreed to be reduced to 10 rounds or 15 rounds maximum for semi automatic center-fire high powered rifles and detachable magazine fed shotguns, then that would at least tactically curb massacres such as Columbine or Aurora though subtle. However, because of the need to uphold democracy safely, if the 10 or 15 round magazine point were ever passed as a bill then it would be required to severely bolt down the 2nd amendment against any more restriction or change to ensure no more power disabling and grab. e.g. If reduced to 10 round by law , getting a 15 round magazine is alike concealed carry or machine gun permit! At any time in history, too many cowards and snivelers and crims have an invested interest in swaying the power structure of government and law to their favor because they do their work by legal writ or slander. If magazine capacity were ever changed, to ensure the incentive to forget trying it remains, the 2nd amendment personal and political society protections would need to be bolted down to almost untouchable ever again against change unless an actual civil war occurred ! === They never quite tell you this too !!! but one of the biggest single threats against democracy and human rights are "hand to hand combat experts(note: this can almost be thin of appearance - can appear average build and muscle)" and a variant much more physically heavy alike a weight lifter similar to a commando is a specialist bouncer security guard! Hence fire-arms and AR-15 ideal for home defence with a low power propellant and 10 round magazine, but i hear yanks need to learn to never leave a firearm unattended , and need to understand to use a "gun locker" for extra weapons and ammunition less used , also to understand how to remember by protocol sequence (habit) whether their weapons are secured, they have too many accidents and too many children accessing their guns accidentally !!! === THIS IS THE WRONG ANGLE AT "MASSACRE CONTROL" FOLLOWING IS NOT A FIX: ...."The panel also offered some new recommendations, such as requiring serial numbers to be etched on shell casings for ammunition; requiring any person seeking a license to sell, purchase or carry a firearm to pass a suitability screening test; and to allow — at a judge's discretion — the opportunity to temporarily remove firearms, ammunition and right-to-carry permits from a subject of a restraining order or civil protection order".... FINALLY! THERE ARE "TWO MASSACRE GUNMAN TYPES" WITH INTERCHANGEABLE ATTRIBUTES TO THEIR PROPERTIES , 1. Murder Suicide ( *Public / Private) 2. Victim Indiscriminate Public Attack Some standard Compound screening protection procedures... 1.With a school such as Newtown Sandy Hook, there was no fence(smallest pupils can climb in or out with mild difficulty at worst) around the school allowing implied representation and signifying adherence to "approach" and "leave" "correct protocol", and thus some screening fence, official entrances, and paths. Neither was there a buffer distance for parking cars from these official entrance exits and paths ! 2.Location was not good in Newtown, particularly it appears for the size of the school area, most of it bordered waste-land or farms without proper line of site clearance. (3. After hours lighting is another) Metaphorically the same method type of tactic as fire-exits! It appears too that security for large numbers of people present in the one location (the principles of troubles breaking out) does not have in a country with firearms the correct fast response of "unarmed handler hand to hand security"(school or movie theater) in FULL armor against "high powered rile"(quite a heavy lump) , aside whether there are trust-able personnel whom can carry concealed weapon as caution. Obama should stop citing Australian statistics, they are not a point!!! Crudely it can be expressed for 100 years as: Australia: 75 percent total homicides by "beating and non-firearm weapon" - max. population density (Sydney) 1/4 of USA environment (never more than 50 gun homicide ever p/year in 100 years (one exception of 80) http://www.dailytelegraph.com.au/news/nsw/docs-shame-file-as-38-child-deaths-erased-from-records/story-e6freuzi-1225938381269 ) USA: 75 percent total homicides by "firearm" - in past 10-15 years has decreased from 8 p/100,000 to 4 p/100,000 of population with same mapping trend as Australia because of GPS,Internet,High dpi camera,mobile phone (Australia had CAD introduced in police vehicles apart DVP scrambling , CAD is Computer Aided Dispatch to incidents or other instant information alike an internet). (Off side parity to contrast) Too , mass killing in Australia without a firearm has occurred since 1996 and 2000 many times! http://www.dailytelegraph.com.au/news/nsw/jeweller-angelos-koots-admits-to-making-submachine-guns-at-his-seven-hills-home-and-supplying-them-to-bikie-groups/story-fni0cx12-1226760983916