What You Need to Know About the Bump Fire Stock Used in the Las Vegas Mass Shooting

The media should be able to provide accurate facts about what they are reporting on.

Details of the Las Vegas massacre are becoming available.

Las Vegas police confirmed that during the attack, the shooter used semi-automatic rifles equipped with ‘bump fire stocks.' If you are like most people, this is the first time you've heard the term bump fire stock. No shame in that, but here's the problem…

Mass media contributors routinely make inaccurate statements about firearms. Reporters saying the ‘AR' in AR15 stands for ‘assault rifle' is one example. The media uses ‘semi-automatic' and ‘fully-automatic' interchangeably. It's wrong, and it's no different than calling a cigarette lighter a flamethrower. Intentional or not, the effect of inaccurate reporting causes a misunderstanding of the facts. Instead of gaining knowledge from the news, people get conflated, inaccurate garbage. This makes substantive and beneficial conversations all but impossible.

Some Background Information:

Reporters continue to say, bump fire stocks ‘convert a semi-automatic rifle into a fully-automatic machine gun.' It's not true. But to understand why you need to know the core difference between a semi and fully-automatic firearm.

Semi-automatic firearms:
A semi-automatic firearm fires only one shot when the trigger is squeezed. There are semi-automatic handguns, rifles, and shotguns. The ‘semi-automatic' part is due to the fact that the trigger is reset not by the shooter but through the cycle of operation of the firearm.

Fully-automatic firearms:
A fully-automatic firearm can fire multiple rounds with a single pull of the trigger. Fully-automatic firearms are sometimes referred to as ‘machine guns.'

Reporters like to use the term ‘military grade weapons' especially when talking about the AR15. It's the civilian version of the military's M16 or M4. They look the same but function differently.

The AR15 is semi-automatic, capable of firing one shot each time the trigger is pulled. The ‘military grade' M16 or M4 can be fully-automatic or have a ‘burst' mode that can fire three rounds with a single trigger squeeze.

The AR15 is semi-automatic only. One shot per trigger squeeze. Fully-automatic rifles can fire 3 round burst or continuously with a single trigger squeeze.

I want to make this point now that we have the basics down.

No military in the world uses a semi-automatic AR15. People cannot walk into any gun store, and walk out the same day with a fully-automatic, machine gun. When you hear a reporter say the AR15 is military grade, fully-automatic or refer to it as a machine gun they are either ill-informed or lying.

This distinction between semi and fully-automatic may seem subtle and unimportant. But it is this difference that defines our firearm laws and is important to understanding the bump fire stock.

Legislation of Fully-Automatic Firearms

In 1929 the Saint Valentines day massacre took place. And in 1933 there was an assassination attempt of President Roosevelt. Similar to modern ‘mass shootings' these events were the catalyst of the National Firearms Act (NFA) of 1934. That act regulated the following:

  • machine guns
  • silencers
  • short barreled shotguns
  • short barreled rifles
  • explosives like grenades

The NFA and subsequent laws like the Gun Control Act of 1968 made fully automatic-firearms expensive and difficult to purchase. Only special licensed gun dealers can even purchase or sell these highly regulated firearms, while some  states have outright banned them.

Why not just ban ‘AR15 style' firearms?

The AR15 is a popular rifle for competition shooters as well as an excellent home defense weapon.

I've heard the question ‘why don't we just ban all AR15's. You know, just the scary looking black rifles with plastic handguards and tactical lights? Well because to do so, would mean banning firearms based not on caliber, the rate of fire or anything remotely logical. It would be banning guns based on appearance.

Strip off the exterior, and the AR15 is no different than most rifles. Even those popularly used for hunting. Rifles with wooden stocks look less intimidating, sure. But often times they shoot much larger caliber bullets, at higher speeds and greater distances. In other words, banning ‘AR15 style rifles' would require nearly every rifle to be banned, and wouldn't even make people safer.

Americans could still own their ‘safer' single shot bolt action guns … like the type used to kill President Kennedy.

What is Bump Fire?

Bump fire is nothing new. The concept uses the reciprocating motion of the rifle to pull the trigger. The rearward movement of the rifle (recoil), not pressure from the shooters finger, acutes the trigger. This allows the gun to be fired more quickly.

This is an AR15 fitted with a Bump Fire Stock from Slide Fire.

Bump fire can be accomplished many different ways. One simple method is holding the rifle at the hip. Placing the trigger finger through the trigger guard and through the shooters belt loop. The rifle is pushed forward, the trigger is actuated, the rifle oscillates and … ‘bump fire' occurs. The method is inaccurate and pretty pointless.

A few companies created products that seized on this phenomenon. The device replaces the buttstock and pistol grip of the rifle. The shooter places their finger inside of the trigger guard and to the back of the device. The first shot is fired, and the device allows room for the rifle to reciprocate inside the stock. As long as the shooter applies consistent forward pressure on the rifle and the finger remains in place, the trigger will be pulled each time the rifle recoils. This method allows the shooter to shoot faster and maintain some accuracy.

It may seem complicated but this video from Slide Fire shows how their product works.

Is it Legal?

In 2010 President Obama's Justice Department, led by Eric Holder made a decision on the legality of the bump fire stock. The DOJ ruled that the device did not violate the Federal Gun Control Act or the NFA.

How did the DOJ come to this conclusion? The device did not modify the internals of the gun to allow fully-automatic fire. Even though the process is being aided by the recoil of the rifle, the trigger still must be pulled for each shot to be fired.

The bump fire stock remained mostly a novelty item. Owners found they were a fun way to quickly burn through a ton of ammo (and money) at the range. Additionally, users learned that shooting at higher rates of fire decreased accuracy.

Trained shooters know they can be much more accurate and nearly as fast firing shots with individual trigger squeezes, instead of a three-round or fully-automatic burst of fire.

Because of these reasons, the bump fire stock was not something typically found on sport shooters or self-defense rifles.

Former U.S. Attorney General Eric Holder

Did It Make a Difference During the Shooting?

Anyone who says definitively the number of lives that would have been lost had the shooter not used this device is speculating. One fewer, 10 fewer, the same, 2 less, there is no true way to know.

Did it allow the shooter to shoot more quickly and thus shoot more rounds in a shorter period of time? Maybe, but the rate of fire is subjective based on a few variables.

  • type of firearm
  • caliber
  • magazine capacity
  • proficiency of the shooter
  • condition of the firearm

The cyclic rate of fire of a fully-automatic M4/M16 is in the neighborhood of 800 rounds per minute.

The cyclic rate of an AR15 is around 600 rounds a minute, with the shooter pulling the trigger over and over.

There are many variables that affect the rate of fire of a firearm.

Cyclic rates of fire on an AR15 with a bump fire stock vary. Why? It takes some time to get used to the amount of pressure needed to keep the gun functioning. But, it is safe to say that the rate of fire would be increased from a standard AR15. How much, is impossible to exactly say, but a rate of fire near 800 rounds per minute would not be unrealistic.

Adding the device increased the rate of fire about 33%. So it's easy to extrapolate these numbers and say he was able to murder 33% more people right? Not so fast.

Even with this increased rate of fire, the shooter still must change magazines. Magazine capacity and ability to change magazines quickly is a factor in the actual rate and number of rounds fired. The condition of the firearms is a factor. Firing at a high rate can cause malfunctions unless the firearm is maintained. Stoppages will obviously slow the number of rounds the shooter can fire. Also, the shooter's abilities must not be overlooked. Particularly when it comes to firing at a distance and a high rate. To be effective the shooter needs a moderate level of training and stamina to continue shooting even if only a few minutes.

The point is, there are many variables that go into the rate of fire, besides the maximum cyclic rate of the gun itself. So drawing a straight correlation between the rate of fire and number of people murdered is not accurate.


We have two major questions here:

  1. Will banning of these devices stop future shootings or had an outcome on the Las Vegas massacre?
  2. Should these devices be banned?

As for the first question:

In the coming months, I am quite sure bump stocks will become outlawed or regulated. How this would actually play out, is unclear. Would people who own them be ‘grandfathered' in? Do owners have a period of time to turn them in before they become felons? What should the punishment be for owning one?

Creating legislation for a diverse population of over 300 million people is complex. Phrases like ‘just ban them' or ‘we have to do something' oversimplify complex issues. Add into the matter, that legislation is often times too vague or over-reaching, and you quickly reach an impasse.

Will making bump stocks illegal stop another incident like the Las Vegas massacre from happening?

Absolutely not. The major reason this incident was so horrific was the tactical advantage the shooter had by being 32 floors above the crowd. That combined with the density of the crowd, was a perfect recipe for disaster, bump stock or not.

And it begs mentioning, that even if these products are outlawed, the ability to bump fire a semi-automatic rifle is so easy, that it can be accomplished with items every person has in their home, including a pair of jeans.

The shooter had tactical advantages beyond the rate of fire of his rifles, that made this incident especially deadly

As for the second question. While I obviously have an opinion on the banning/regulation of these devices, I purposely left it out of this article. Why?

I simply want readers to know the facts about bump fire stocks; what they do and don't do. Understand what makes a semi-automatic different from a fully-automatic firearm, and a little about our gun laws.

Share this with those who don't know these things. When we are all knowledgeable on the subject, we can logically have a discussion. Because we can't have meaningful dialog on these topics, if we generalize or speak ignorantly.

I am going to go out on a limb here and say that not everyone who feels bump stocks should be made illegal, wants to ban all firearms. Similarly, not everyone who fears banning them supports mass murder.

We are stronger as a country when we set aside anger and bias, and work together for solutions.

Most importantly remember this. You cannot legislate evil out of people. Evil people will find ways to do evil things. After all, murder is illegal and that fact hasn't stopped a single murder since the begining of time. Looking to the government to solve problems of the heart is looking in the wrong place. Hatred and anger are what allowed this maniac to commit this horrible act. This same hatred and anger will not help us reach solutions. It only deepens the wounds.

Stay safe and God Bless.

About Matthew Maruster

I follow my Lord and Saviour Jesus Christ who is the eternal co-equal Son of God. I currently live in Columbus, Ohio with my wife and daughter. I served in the Marine Corps Infantry. I was a Staff Sergeant and served as a Platoon Sergeant during combat in Iraq. After I was a police officer at a municipal agency in San Diego County. I have a Bachelors's Degree in Criminal Justice from National University. MJ Maruster Defense.


  1. Jacob Paulsen on October 10, 2017 at 11:12 am

    Great overview Matthew!

  2. Bill MacAusland on October 12, 2017 at 9:46 am

    Thank you like many people I had never heard of bump stocks and did not know how they functioned. I have been around guns all my life, I am 80 years old and belong to two sportsman’s clubs and I am also a hunter and a supporter of the second amendment. My son has an AR-15 and also his buddy and they use them for target shooting at the range he is also an ex service Marine Corps. I cannot understand why anyone would want these stocks other that what this nut did with it and when AG Holder is involved it brings more questions. I am against any attempt to ban any fire arms or to change the second amendment in any way. Here in Massachusetts we have an AG that is banning magazines
    that hold more than 10 rounds and the sale of AR-15 and other guns like Glocks. Keep up the fight and God Bless

    • Matthew Maruster on October 13, 2017 at 7:14 pm

      Hi Bill. Sometimes I have to wonder if the politicians who craft gun legislation are as stupid as they seem. Or if they purposely conflate terms and definitions to make the laws so confusing that no one can understand them. Keep fighting the good fight in Mass. !!

  3. Doug on October 13, 2017 at 10:32 am

    Excellent article Matt. I’ve heard too many people repeating the media misinformation to be comfortable thinking we’ll get to a solution that won’t effect our rights.

    • Matthew Maruster on October 13, 2017 at 7:11 pm

      Thanks Doug! The misinformation out there is extremely aggravating. So glad you liked the article.

  4. William Smart on May 21, 2018 at 8:44 pm

    Great article Matthew. Like a lot of people I never heard of the bump stock, of course I don’t own an AR-15 so I might be out of the loop. Anyway if anything is to be banned why not try banning what these idiots want “PUBLICITY”. If the media would stop inundating us with thier picture and names maybe it will relieve some of the excitement of the infamy. Blur out the picture just say “shooter” no names no background make them as annonimous as they were before. Like you said evil people will find ways to do evil. Should we ban the car because drunk drivers use them as weapons, or the knife, hammer, phillips screwdriver, and so on and on, NO it’s evil people not evil objects.
    One more thing, try telling a antigunner that the AR in AR-15 does not stand for Assualt Rifle is like impossible!

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