# Would the Ammunition Fired by an AR-15 Penetrate a Typical School Classroom Door with Lethal Force Remaining? **URL:** \ **Category:** Factual Questions\ **Created:** [June 7, 2022, 2:34pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808 "2022-06-07T14:34:05Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [June 9, 2022, 1:15pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/21 "2022-06-09T13:15:17Z")
> [@Chronos](#): > > A bigger consideration than deflection by the door would be blocking line of sight. It doesn’t matter precisely what direction the bullet exits the door in, if the shot wasn’t aimed to begin with, and even a paper door could prevent a shooter from aiming at a specific target. True, but if the shooter emptied both guns into the door in rapid succession, I wouldn’t like your odds. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 10, 2022, 3:07am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/22 "2022-06-10T03:07:36Z")
Well, hopefully the people in the room are not in front of the door where they could be hit but, rather, to the side where there is no angle to be shot through the door. In that case, if the door prevents entry, it does its job. I do not know if cinder blocks (which seem the common wall material in most schools) is protection enough from someone trying to shoot through the walls. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 10, 2022, 3:24am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/23 "2022-06-10T03:24:02Z")
> [@Whack-a-Mole](#): > > I do not know if cinder blocks (which seem the common wall material in most schools) is protection enough from someone trying to shoot through the walls. I wouldn’t count on it: [![](https://img.youtube.com/vi/3Cgkczml_Cc/maxresdefault.jpg "223 vs 308 - Cinder Block Watermelon Test") ](https://www.youtube.com/watch?v=3Cgkczml_Cc) Stranger ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 10, 2022, 4:05am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/24 "2022-06-10T04:05:59Z")
Doesn’t an AR-15 fire a .223? It seemed that failed in the video until a second shot was made. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [June 10, 2022, 4:24am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/25 "2022-06-10T04:24:39Z")
ARs in general terms consist of a “lower” or receiver that contains the trigger group, grip, and attachment for the stock. The “upper”, which is attached via two pins, consists of the barrel assembly and hand guard. The upper can be had in calibers ranging from 22LR rimfire up to 50 caliber round. .223 or 5.56 NATO are the most common. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 10, 2022, 6:35am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/26 "2022-06-10T06:35:21Z")
> [@Whack-a-Mole](#): > > Doesn’t an AR-15 fire a .223? It seemed that failed in the video until a second shot was made. Yes, the block stopped the first round. An AR-15 pattern rifle accepts [removable box magazines carrying .223 Remington/5.56 x 45 mm NATO ammunition from 10 to 40 rounds](https://gunmagwarehouse.com/all-magazines/rifles/magazines/ar-15-magazines) without going to drum magazines. (There are, as @GaryM notes, other calibers that can be fired in that platform by changing the upper receiver including the .300 AAC Blackout and 6.8mm Remington SPC that have heavier bullet weights and offer even better penetration.). The typical magazine capacity is 30 rounds (where allowed by law); with that number of rounds you could easily blast a man-sized hole through an unreinforced cinder brick wall or send a large volume of shots into a room regardless of whether a door was secured or not, and of course [a moderately skilled person can swap magazines in that rifle in a few seconds.](https://youtu.be/5iMTE3gU49I) In general, most objects that people think of as secure cover against gunfire such as wooden tables or doors, sheet metal car bodies, exterior house walls, et cetera are quite permeable to even relatively low energy centerfire rifle rounds like the .223 Remington/5.56x45 mm NATO, and of course an even moderately “high powered” .30 caliber or 7mm rifle round will punch right through a cinder block with plenty of residual kinetic energy. The entire notion of making classrooms into secure fortresses than can withstand deliberate assault by an individual armed with a centerfire rifle (and often with school shooters having knowledge of how to enter and move around the facility) is a kind of survivalist fantasy that doesn’t reflect reality any more than plans to arm teachers or equip children with bulletproof backpacks. Stranger ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 10, 2022, 11:53am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/27 "2022-06-10T11:53:15Z")
First of all, cinder blocks are a lot more substantial than wooden tables, sheet metal car bodies, or most exterior house walls. And second, yes, heavier rounds can destroy a cinder-block wall, but even there, it’ll slow down an attacker considerably, and cinder blocks would still protect against lighter rounds. ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [June 10, 2022, 3:11pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/28 "2022-06-10T15:11:58Z")
> [@Stranger\_On\_A\_Train](#): > > The entire notion of making classrooms into secure fortresses than can withstand deliberate assault by an individual armed with a centerfire rifle (and often with school shooters having knowledge of how to enter and move around the facility) is a kind of survivalist fantasy that doesn’t reflect reality any more than plans to arm teachers or equip children with bulletproof backpacks. So the suggestion that schools decorate their classrooms with colorful ballistic blankets is fantasy? I am shocked, shocked! ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 10, 2022, 4:07pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/29 "2022-06-10T16:07:49Z")
> [@Chronos](#): > > And second, yes, heavier rounds can destroy a cinder-block wall, but even there, it’ll slow down an attacker considerably, and cinder blocks would still protect against lighter rounds. Not as much as you’d think: [![](https://img.youtube.com/vi/0tq_39a6SDc/maxresdefault.jpg "9mm vs 45 ACP - Cinder Block Test") ](https://www.youtube.com/watch?v=0tq_39a6SDc&t=1m55s) A cinder block in a wall is somewhat reinforced by the blocks around it but having demo’d cinder block structures by hand with an 8 lb sledgehammer (a nasty and exhausting business that I don’t recommend) I can say that they aren’t nearly as resilient as people generally imagine; they certainly are not the structural equivalent of reinforced concrete or even terracotta brick. > [@Marvin\_the\_Martian](#): > > So the suggestion that schools decorate their classrooms with colorful ballistic blankets is fantasy? I am shocked, shocked! Well, at least if they are colorful and quilted with inspiring quotes they’ll be of some aesthetic value. Stranger ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 10, 2022, 8:37pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/30 "2022-06-10T20:37:44Z")
\<\< Deleted by poster…not an FQ response \>\> ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [June 17, 2022, 2:34pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/31 "2022-06-17T14:34:42Z")
> [@tofor](#): > > I’m fairly certain that last part is a myth. We have even discussed it before (12 years ago!) though without any solid conclusion. And yet [anti-personnel mines](https://en.wikipedia.org/wiki/Anti-personnel_mine) are designed to maim, not kill for that very reason. I don’t think the 5.56 caliber was chosen _specifically_ because of the ‘wound, not kill’ factor but rather it was deemed as ‘acceptable’ because of the other characteristics. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [June 17, 2022, 2:53pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/32 "2022-06-17T14:53:47Z")
> [@tofor](#): > > I’m fairly certain that last part is a myth. We have even discussed it before (12 years ago!) though without any solid conclusion. If you have a cite for that, maybe resurrect this thread: It is less about wounding being _better_, but that wounding is _nearly as good_. And if you can carry more ammunition, you can produce more wounds, and “nearly as good” becomes “superior”. So it’s anyone’s guess why the Army is now [deep in the process of evaluating a new 6.8mm round](https://www.military.com/daily-news/2022/05/02/how-well-do-armys-new-guns-perform-thats-classified-soldiers-will-carry-more-weight-less-ammo.html) to replace the 5.56. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [June 17, 2022, 2:56pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/33 "2022-06-17T14:56:35Z")
> [@HMS\_Irruncible](#): > > So it’s anyone’s guess why the Army is now [deep in the process of evaluating a new 6.8mm round](https://www.military.com/daily-news/2022/05/02/how-well-do-armys-new-guns-perform-thats-classified-soldiers-will-carry-more-weight-less-ammo.html) to replace the 5.56. Body armor, basically. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 17, 2022, 5:25pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/34 "2022-06-17T17:25:34Z")
> [@engineer\_comp\_geek](#): > > Body armor, basically. The round was selected for penetration versus body armor and increased accuracy and lethality at longer ranges. Neither were a concern during the Vietnam War when the M16 and the 5.56x45mm NATO was first deployed, and not a significant factor in the relatively short engagement ranges in urban combat that was the primary concern for a land war in Europe and where a lot of fighting in Iraq occurred, but at the much longer ranges experienced in the mountain fighting in Afghanistan the limited range of the 5.56x45mm NATO round, especially when fired in the 14.5 in barrel of the M4 carbine, proved to be so limiting that the US Army and Marines started deploying upgraded versions of Vietnam-era M14 rifles (M14 Enhanced Battle Rifle and M39 Enhanced Marksmanship Rifle) to deal with ground engagements at longer ranges where air support was not readily available. These 7.62x51mm NATO rifles weren’t deployed widely because of the limited inventory, inexperience with basic infantry firing such a hard recoiling round, and heavier weight of the rifle and ammunition on top of all of the body armor and electronics (including batteries) which the modern soldier and marine carry and were predominately in use with special operations but the advantages of the more powerful round were quite evident. In future ‘near-peer’ and proxy conflicts which may take place in a variety of different terrain and with adversaries which may be comparably equipped to US troops, a rifle capable of accurate fire at longer ranges and penetrating body armor was considered more desirable over minimizing rifle weight and maximizing the rounds of ammunition carried. The 6.8 Remington SPC intermediate cartridge (based on a 5.56x45 mm case) proved quite effective and popular with special operations, so a 6.8 mm cartridge using the 7.62x51mm case providing essentially the ballistics of a .270 Winchester but in a case length compatible with a short stroke piston action, was found to be a good choice as a full power battle rifle cartridge in the modern, softer recoiling Sig MCX SPEAR firing the .277 Fury round, issued as the standard infantry rifle. How well that heavier rifle and ammunition will actually work in reality is subject to debate, with predictably some people arguing that it will be abandoned _en masse_ in favor of a lighter weapon and ammunition for most front line infantry and others suggesting that it will prove more capable than the M4 despite those factors, but only time and experience will tell. Stranger ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [June 17, 2022, 6:31pm UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/35 "2022-06-17T18:31:27Z")
If you want to read an intelligent expose of the Army’s treatment of the AR-15 / M-16 I suggest this article by James Fallow. It’s a fairly long article but very well written and easy to follow. It is absolutely chilling to see how the bureaucracy crippled the nearly perfect AR-15 into the troublesome and unreliable M16. Thousands of our friends and family in the armed forces died because of terrible decisions by the Ordnance Corp. > **[M-16: A Bureaucratic Horror Story](https://www.theatlantic.com/magazine/archive/1981/06/m-16-a-bureaucratic-horror-story/545153/)** > > Why the rifles jammed ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [June 18, 2022, 1:20am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/36 "2022-06-18T01:20:09Z")
I recall many many years ago, helping an acquaintance dispose of his cat (needed to - the thing had viciously attacked the paper boy for the second time). He put in a box, and a bunch of us drove out of town. He shot it with a moose rifle (303?) from about 50 yards and the result was basically the front half was hamburger. Whereas a moose he had shot that I saw was pretty much intact - I imagine the overall size of the flesh container affects how much damage. Those bullets can do serious damage to flesh. I have also done target practice with a 303 once. The target was a normal metal spray can of paint under pressure at about 100 yards. At least twice we hit it a glancing shot and the can just danced away with a dent. Hit it straight on and it sprayed paint. SO I can see the fact that deflection can be an issue. I agree, I get a kick out of those Hollywood dramas where a table or a behind a bar (probably 3/4 particle board and veneer) is an excellent protection against gunshots. Plus most indoor construction the last 70 years or more is just two layers of drywall. A thinking shooter would aim for the wall beside the doorknob if he thought there was someone trying to open the door. (IIRC, the gunman in the Vegas hotel used a remote camera and shot at security through the walls when he saw them coming). Even more funny is using an open car door as a shield - that’s got to be even less protection. But then, Hollywood uses low velocity rounds obviously, because a round that takes out the back window of a car usually does not even damage the windshield. I assume spraying the door of a room, even at an upward trajectory, still risks fragments hitting people lying on the floor. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 19, 2022, 1:22am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/37 "2022-06-19T01:22:03Z")
> [@Stranger\_On\_A\_Train](#): > > The round was selected for penetration versus body armor and increased accuracy and lethality at longer ranges. Neither were a concern during the Vietnam War when the M16 and the 5.56x45mm NATO was first deployed, and not a significant factor in the relatively short engagement ranges in urban combat that was the primary concern for a land war in Europe and where a lot of fighting in Iraq occurred, but at the much longer ranges experienced in the mountain fighting in Afghanistan the limited range of the 5.56x45mm NATO round, especially when fired in the 14.5 in barrel of the M4 carbine, proved to be so limiting that the US Army and Marines started deploying upgraded versions of Vietnam-era M14 rifles (M14 Enhanced Battle Rifle and M39 Enhanced Marksmanship Rifle) to deal with ground engagements at longer ranges where air support was not readily available. Why do they care about range so much? The report below, done in the early 50s, showed hit effectiveness was good only to 100 yards and decreased rapidly out to 300 yards. Who cares if a soldier’s rifle can technically hit something at 800 yards but they almost certainly won’t hit anything much past 300 yards? Just a waste of ammo. (Of course, it makes sense for the marksmen to have weapons that can reach out that far but I think they are a relative few in the military.) While the study is old I think I have read elsewhere that those numbers have not really changed much (but I cannot find that cite now). > The capabilities of the infantry rifle were explored. Data wer e obtained on the frequency and distance by which riflemen missed targets, and the distribution of hits at different ranges the ranges of engagement in battle and the physiological wound effects of shots with differing ballistic characteristics. A study of the data led to the following conclusions 1 Hit effectiveness with the M-1 rifle is satisfactory only up to 100 yds. and declines rapidly to low order at 300 yds., the general limit for battlefield rifle engagements 2 a pattern-dispersion principle in the hand weapon would tend to compensate for human aiming errors and increase hits at ranges up to 300 yds. and 3 missiles with smaller caliber than standard could be used without loss in wounding effects and with logistical advantage and 4 hit lethality could be greatly increased by using toxic missiles. [SOURCE](https://apps.dtic.mil/sti/citations/AD0000346) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 19, 2022, 2:08am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/38 "2022-06-19T02:08:42Z")
In a war, you’re not aiming at individual soldiers, anyway. As the old saying goes, you don’t need to worry about the bullet with your name on it; you need to worry about the one “to whom it may concern”. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 19, 2022, 2:27am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/39 "2022-06-19T02:27:09Z")
> [@Chronos](#): > > In a war, you’re not aiming at individual soldiers, anyway. That may be true for your average infantryman on patrol but not for a designated marksman or special operations. In an open mountainous region where someone is shooting at you from 300 meters, you want to be able to shoot back and eliminate that target, not just blaze away hoping a round randomly hits them. Stranger ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [June 19, 2022, 11:36am UTC](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808/40 "2022-06-19T11:36:02Z")
> [@Sam\_Stone](#): > > For example, the .5.56 NATO round the AR-15 uses has a muzzle energy of about 1200 foot pounds. 7.62X51 NATO rounds as used in most other nation’s equivalent weapons generate over 2,700 ft-lbs from a heavier, slower bullet. What nation uses 7.62 NATO as their primary infantry rifle cartridge? Are you sure you’re not confusing 7.62 NATO with 7.62x39? The muzzle energy from a 7.62x39 is closer to 1600ft-lbs. It’s more than 5.56 NATO, but not 2+ times greater. [Previous page](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808.md?page=1) [Next page](https://boards.straightdope.com/t/would-the-ammunition-fired-by-an-ar-15-penetrate-a-typical-school-classroom-door-with-lethal-force-remaining/965808.md?page=3)