The Myth of Limiting Magazine Capacity

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This blog is an excerpt from the book Countering the Mass Shooter Threat by Michael Martin. Click here to purchase your own copy of this riveting 191-page examination of the myths and science surrounding “assault weapons,” magazine capacities and the threat of active shooters.

The argument that “high-capacity” magazines are partially (or mostly) to blame for mass shootings isn’t a new one. It seemed to reach a fevered pitch in the aftermath of Sandy Hook when the states of Connecticut, New York and Colorado all enacted new limits on magazine capacity. With the 2020 presidential election looming, the topic of magazine restrictions is again rearing its ugly head.

The argument put forward by these states was based upon the belief that it was a high rate of fire enabled by magazine capacities of 30 rounds or more that allowed perpetrators to murder a large number of victims in a short period of time. The theory was that by reducing magazine capacities by up to two-thirds, the number of victims would be greatly reduced at future mass shootings. This theory wasn’t one that gun-control advocates latched onto halfheartedly. It was really the centerpiece of their proposals on how to reduce or eliminate future mass shootings.

That begs the question: Exactly how many rounds can be fired per minute when using a magazine capacity of five rounds, 10 rounds or 30 rounds, and would a lower round capacity have affected the outcome at any mass shooting?

A chart showing columns for firearm magazine capacity, reloads required per minute and rounds fired per minute

Let’s look at the actual rates of fire attainable with three different-sized magazines. This table shows how many rounds can be fired per minute using a moderate rate of fire of two rounds per second and a moderate magazine change rate of three seconds. Someone with practice would be able to fire at about twice this rate. As you can see, the table shows that reducing magazine capacity by two-thirds doesn’t reduce the rate of fire by two-thirds; it simply means that more magazine changes are required per minute.

The actual reduction in rate of fire when going from a 30-round magazine to a 10-round magazine is about 25 percent. The math is simple: With 30-round magazines and a moderate rate of fire of two rounds per second, a shooter would be able to sustain a rate of fire of about 100 rounds per minute. Using 10-round magazines, that same shooter would be able to sustain a rate of fire of about 75 rounds per minute. The decrease in rate of fire would occur because the shooter would need to go from about 3.3 magazine changes per minute to about 7 magazine changes per minute. If dropping to five-round magazines, that same shooter would be able to fire 55 rounds per minute.

Just to confirm that I’m not manipulating these numbers to make any particular case, you can mimic this test yourself by pressing your index finger twice per second, as though you were shooting a gun. You’ll recognize pretty easily that you can press your finger much faster than twice per second, so we could easily double the rates of fire shown on the table. In a moment, you’ll see why I’m satisfied with the data as we attempt to answer the question: Would a lower magazine capacity have affected the outcome at any mass shooting? The “magazine” argument insinuates that if the rate of fire of active shooters can be reduced to the limits imposed by five or 10-round magazines, the number of victims at mass shootings would be significantly reduced.

Comparative Rates of Fire

Before we answer that question, let’s look at these rates of fire visually. On the linear scale shown below, I’ve placed the three rates of fire possible when using five, 10 or 30-round magazines on the right side of the scale. If we were to ban all 30-round magazines and replace them with 10-round magazines, we’d be moving the theoretical maximum rate of fire from 100 rounds per minute to 75 rounds per minute — a reduction of 25 percent.

A chart showing comparative rates of fire of historic as well as modern firearms and the effective ROF of 10 of the deadliest mass shootings in American history

 

To give some comparative rates of fire, jump back more than 240 years to take a look at what rates of fire used to be. Let’s start with the muzzle-loading Kentucky rifle, which was the preferred rifle of the American patriots during the Revolutionary War. As a muzzle-loading firearm, the Kentucky rifle took four separate steps to load, but an experienced shooter could maintain a rate of fire of about five rounds per minute. I’ve placed that rifle on the far left side of the scale. As firearms technology advanced, self-contained cartridges were developed, leading to the development of the Sharps single-shot rifle in 1848. Loading one round at a time, the Sharps more than doubled the rate of fire — up to an average rate of 12 rounds per minute. Fast forward to the Civil War, when the height of firearms technology was the lever-action Henry rifle with a sustained rate of fire of about 30 rounds per minute.

Lastly, I’m going to drop in the rates of fire for several other firearms types. Five-shot revolvers and five-shot pump-action shotguns are able to sustain a rate of fire of about 35 rounds per minute, which is a bit slower than semi-automatics using five-round magazines since they take slightly longer to reload. I’ve also included a model 1911 pistol which uses a seven-round magazine and can sustain a rate of fire of about 65 rounds per minute. Finally, the Glock 19 uses a 15-round magazine, with a rate of fire of about 85 rounds per minute.

The magazine argument crumbles even further when looking at the rates of fire of several mass shooters, including those shown in the table below (at the time I’ve compiled this data, no information has been released about the number of rounds fired by the Orlando shooter). These shooters all fired at a rate significantly lower than the limit established in Connecticut, which is one of the lowest in the nation. A high rate of fire apparently didn’t matter to any of these shooters.

A chart comparing effective rates of fire of 10 of the dealiest mass shootings in American history

Let’s state these facts with a little perspective. The cowardly Newtown shooter fired at a rate of fire no faster than the 150-year-old lever-action Henry rifle — even though he had ten 30-round magazines and an AR-15. The despicable Fort Hood shooter was one-third slower than that, while the mass murderer at Virginia Tech was 50 percent slower. Even the San Bernardino shooters, who carried AR-15s and 30-round magazines, fired at a rate no faster than one round every 3.3 seconds. This is 40 percent slower than the lever-action Henry. The coward who shot up a theater in Aurora, Colorado, fired at a rate no faster than the 170-year-old single-shot Sharps rifle — even though he had a 100-round magazine. Keep in mind, the Sharps rifle has a capacity of one round! Finally, the Red Lake shooter and the Columbine shooters fired at a rate of fire no faster than the 240-year-old, muzzle-loading flintlock Kentucky rifle.

Now, this isn’t fuzzy math I’m using. For example, it is well-documented that the San Bernardino shooters fired 65 to 75 rounds during their five-minute attack. If just one of the shooters fired all of the rounds, the rate of fire would still just be 14 rounds per minute, or one round fired every four seconds. If both shooters fired an equal number of rounds, their individual rates would be no higher than seven rounds per minute, or one round every eight seconds.

You could argue that perhaps the shooter in every one of these cases was simply inexperienced and wasn’t able to press his or her trigger finger faster than once every four to eight seconds. But that’s a pretty silly argument considering how easy it is to test that theory by pressing your finger faster than twice per second while you sit and read this. In the case of the San Bernardino shooters, we have ample evidence that the shooters practiced frequently at a local range.

A simpler explanation of why these shooters had such low rates of fire — and the one that makes the most sense — is that when these shooters had their victims held captive in enclosed rooms and they were the only ones with guns, they simply didn’t need to press the triggers faster than once every four to eight seconds.

When you’re firing at that pace, magazine size simply doesn’t matter.

Unintended Consequences

As every experienced shooter knows, the larger the magazine capacity, the higher the rate of malfunction. A 100-round magazine will malfunction more frequently than a 30-round magazine, and a 30-round magazine will malfunction more frequently than a 10-round magazine. The reason for this has to do with the length of the spring pushing the rounds through the magazine. The longer the spring, the greater the pressure on the initial rounds, resulting in a higher probability of a double feed or of the magazine’s follower becoming misaligned and locking in place, rendering the magazine temporarily useless.

Let’s look at a couple examples: The Aurora, Colorado theater shooter brought one single AR-15 magazine with him, which held 100 rounds. Not only did that make his firearm incredibly heavy and unwieldy, the magazine also failed completely after approximately 45 rounds, and his incredibly slow rate of fire (one round every four to seven seconds, no faster than a single-shot rifle) would indicate that he most likely was fighting misfeeds right up until the point that the magazine failed. Had he been using 10-round magazines, it’s unlikely that any failure would have occurred, and his rate of fire could have been much higher.

Another example: Police reports indicate that at one point during his shooting spree, the Sandy Hook shooter paused, which allowed nine children to flee their classroom. Based upon statements from the children and evidence at the scene, it appears as though the murderer’s AR-15 malfunctioned and he was forced to pause to clear the malfunction.

Evidence of a malfunction included unfired rounds found on the floor, which would be typical of a double feed (when two rounds try to feed into the chamber at the same time). To clear a double feed, the shooter must remove the magazine and retract the bolt to clear the double feed (causing two or more rounds to drop to the floor) before reinserting the magazine and releasing the bolt. Double-feed failures are common when using 30-round magazines that have been filled to their capacity.

These malfunctions are far less common in 10-round magazines because of their shorter springs and lower spring pressure on the initial rounds. Had the criminal been using 10-round magazines, a double feed or other failure would have been far less likely. Now, I’m not suggesting that future victims of mass shootings will be safer if the shooter chooses to use 100-round or 30-round magazines rather than 10-round magazines, but I am suggesting that when politicians who know absolutely nothing about firearms attempt to make firearms policy, they shouldn’t be surprised when their actions don’t have the desired effect.

ENDNOTES: (1) The gunman killed a total of 32 people at Virginia Tech in two separate attacks. For purposes of calculating his rate of fire, only the second attack, where a total of 30 people were killed, is included in this table; (2) Police records indicate that the murderer shot his way into Sandy Hook Elementary at 9:35 a.m. and, at 9:40 a.m. (5 minutes after the shooting began), the last shot was heard, which is believed to be the coward taking his own life. Police entered the school four minutes later, at 9:44 a.m. (nine minutes after the shooting began); (3) Since the San Bernardino shooting involved two shooters, the calculation of rounds fired per minute shows a spread of seven to 14 rounds per minute. If one shooter was responsible for all rounds fired, the rate would be approximately 14 rounds fired per minute. If both shooters fired an equal number of rounds, their individual rate would be approximately seven rounds fired per minute, or one round every 8.5 seconds; (4) The timeline of the Aurora Theater shooting indicates that the killer opened fire at 12:37, the first 911 call was received at 12:39 (two minutes after the shooting began), the first police arrived on the scene at 12:41 (four minutes after the shooting began), police began to surround the theater by 12:42 as witnesses report that there is still “someone actively shooting” inside (five minutes after the shooting began), and the fleeing gunman is apprehended outside the back of the theater at 12:46 (nine minutes after the shooting began); (5) This is a calculated estimate based upon the handgun model used and the number of magazines in the murderer’s possession. The actual number of rounds fired may be far less.

Want to read more? Pick up your own copy of Countering the Mass Shooter Threat by Michael Martin!

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