What Hollywood gets wrong about automatic weapons.

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This week I’m picking up another topic which was inspired by watching the latest Season of Reacher. Last week I spoke about how apprehending the suspected suicide bomber opening scene was a pretty bad judgement call on Jack Reacher’s part, in both the book and the show.

This week (spoilers) I’d like to talk about the chase scene where the impossibly hot baddie is pursuing Reacher and chums:

Amisha is using an AK to spit lead at our heroes’ car. What she doesn’t seem to realise is that Reacher has enabled a magical forcefield which deflects bullets away from any biologically or mechanically important targets in the car. Only goodies get these forcefields, so it’s a good thing she doesn’t realise this or her morale would suffer terribly.

Anyway, I’m not here today to rant about magical protection from bullets. What I do want to talk about is her use and abuse of the weapon’s ability to fire “full auto,” i.e. fully automatically¹. This problem is not unique to Reacher, but this was a bad example of it and I was already on a rant about it, so let’s go.

The problem is this: Hollywood loves weapons firing on full auto, even though it’s something which militaries heavily discourage in real life in the vast majority of situations. But even Hollywood heroes and villains who should know better (e.g. they’ve had military or police training) are incontinent with their fire discipline and weapons handling.

There are three main reasons why soldiers rarely fire full auto: it ruins accuracy, it wastes ammunition, and it accelerates barrel wear. I’ll expand on each of these below.

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Full auto ruins accuracy

Automatic weapons are powerful machines. This might seem like a “well, duh” observation, but many of us (especially Hollywood screenwriters) seem to forget this when we depict them in action.

Let’s do a little comparison, with some round numbers. A 7.62 mm bullet, as spat out by an AK-47, weighs about 10 grammes. It leaves the muzzle at about 700 metres per second. Its kinetic energy is half its mass times its energy squared. When you do the maths, that’s about 2,500 joules of energy per bullet. On full auto it fires 600 rounds per minute, which is ten per second. That’s 25,000 joules per second, which is 25,000 watts, which is 25 kilowatts. That’s 34 horsepower, in old money, or the same as a small motorbike engine.

As if that wasn’t enough of a problem to handle, you need to remember that less than a third of the energy released in a firearm goes into bullet speed. The rest gets dissipated as heat or comes out in the form of violent propellant gases. Add the gases coming out, and your AK-47 is now putting out over 60 kW², which is the equivalent of a small car engine. So, firing an assault rifle on full-auto is like trying to control a car’s engine single handedly:

Think of how hard it would be to control an engine like that, even if you had the tractor-arms of our AI friend above. That’s what firing on full auto is like.

When you squeeze that trigger and the beautiful machinery starts chattering away with its double base notes, the business end of the weapon starts climbing. It takes a lot of strength to keep that weapon pointed in even the approximate direction of the target. It’s not something that you can do with one hand, even if you’re Sylvester Stallone:

Firing fully automatic kills your accuracy, but so what? What if you just want to scare the target? Keep their head down?

While there is something to be said for the suppressive effect of automatic fire (see below—it has its uses), this goes out the window if your rounds aren’t landing in the same postcode as the enemy. Studies have been done on suppressive fire, and it turns out that you need to demonstrate the ability to hit and kill the enemy for your suppressive fire to be effective:

Are the effects of suppressive fire psychological?
byu/OOM-TryImpressive572 inWarCollege

Accuracy isn’t just about whether or not you hit the target, however. More fundamental than that is safe weapons handling. Things like not hitting your own troops or obstacles close to you (where a bullet might ricochet back at one of your buddies) are beaten into every soldier from their earliest days. Full auto removes the ability to control your weapon, and therefore it isn’t taught to soldiers except in very limited situations.

What are these situations? One example would be during the final assault of an enemy position. Whether it’s a ditch-line, a trench, or a room, coming in with your barrel spitting out lead is the default approach in greenfield tactics. You’ll also probably throw or post a grenade in there first, so the rifle fire ensures a belt-and-braces approach. If you’re more than a dozen or so metres from the enemy, however, then single well-aimed shots are what you’ll use.

Another situation where full auto might be justified is in contact drills. These are the quick reactions you make to enemy fire when you’re patrolling. Once you start taking fire, you’ll have to get into cover straight away and start suppressing the enemy with single, well-aimed shots. Until you can get behind that ditch, or if you’re caught out in the open, it makes sense to unload a hail of lead in their general direction. This only works if you’ve got a buddy or three behind you, ready to go when your magazine runs out.

Coming back to our original example from Reacher, it would have been more realistic if the hot baddie’s automatic fire had resulted in zero hits to the good guys’ car. If I was leaning out of a moving car, firing at another moving car, while in a slipstream and with a poor grip on my weapon, I’d be firing single aimed shots. Even then, I’d be delighted to get one round in ten on target.

Then again, in the real world, I’d also be trying to conserve my ammunition, and that’s another thing which full auto ruins.

Full auto wastes ammunition

Full auto is a gigantic waste of ammunition. I mentioned above that the AK-47 goes through 600 rounds per minute. This wouldn’t be out of the ordinary:

All of the above rates of fire make one big, unrealistic assumption: infinite ammunition. An AK-47 will never fire 600 rounds in a minute because its magazine can only hold thirty. That would last you all of three seconds. Even if you had insanely quick mag-changing skills, you’d still be doing extremely well to manage 300 rounds in a minute of full auto³.

In that time, you’d have gone through what might be a typical loadout for a single soldier: ten or so magazines. Aside from ringing ears, you’d have very little to show for your little demonstration in terms of target effect. But you would have significantly lightened your load, at least until the platoon sergeant shows up with another box of ammo for you to load into your empty magazines. Oh, you did what? You threw the empties away? Oh dear, now you’re in trouble.

I used the Steyr AUG during my time in uniform. This Austrian weapon has a very simple fire selection system: half-squeeze the trigger for single shot, fully depress it for full auto. It’s a clever system, but maybe a little too clever for soldiers. When this weapon first came into Irish service in the late 1980s, we asked for, and received, a special modification from Steyr. This was the automatic lockout or ALO, a button that stopped the trigger half-way, disabling automatic fire:

In those rare occasions when we did need to fire full auto, or prepare for the option, the shorthand “ALO up” was used. It was easy to press in the ALO, which would be handy in a pinch, but hard to pop it back out again, while being a visible indicator of your weapon state.

It reminds me of the (probably apocryphal) story about the AK-47 and its fire selector design, where the top position is “safe,” i.e. no firing possible, and the bottom position is single shot. The idea is that a panicked conscript under fire will push the selector all the way down, so the “full auto” setting requires a conscious middle position and the default is single shots, conserving ammunition and accuracy.

It would be a great story if there was any evidence for it, but it’s more likely that these selector positions were the easiest to implement in the design of the weapon.

One solution to the problem of ammunition is the belt and can. Instead of a box magazine which needs changing every 20 or 30 rounds, a belt-fed weapon can keep going for hundreds of rounds.

Notionally, it can go on forever, because there’s no real limit to how long a belt can be, provided you have someone to hold it and someone to fire:

I say notionally because, if you’ve ever tried to fire an endless belt from a machine gun, you quickly run into the third limitation of full auto: barrel wear.

Full auto kills barrels, not baddies

I wrote about this before as part of my long ballistics article, so you can check that out if you want more detail. Suffice to say that firing rounds quickly through a barrel means that heat builds up and can’t dissipate.

The hotter the barrel, the quicker the mechanical wear, so it’s easy to do permanent damage⁴ to a barrel by putting too many rounds through in too short a time. For example:

It happens. The barrel of a 12.7-mm machine gun NSV "Utyos" heated and melted during intense fire.
byu/Adorable-Trust4687 inForgottenWeapons

Machine guns usually come with multiple barrels. A 7.62 mm squad level machine gun might have one spare, while a 12.7 mm (.50 cal) heavy machine gun will have at least two. The crews are supposed to change the barrels after a set number of rounds to ensure that they wear evenly.

An assault rifle won’t have multiple barrels, so it’s on the firer to maintain discipline and not destroy the barrel. Granted, it’s difficult to reach that level of heat when you’re constantly changing magazines, but it’s possible even without full auto if you’ve committed hard enough to the bit:

Coming back to full auto, hot and worn-out barrels are something we never see in film and TV. To be fair, only an armourer or gun nerd will worry about things like that, and our Hollywood heroes are usually not that. They’re far too cool to fret over damaged military hardware.

Conclusion: Full auto is cool

I don’t want to give you the wrong impression here. Firearms are designed to be able to fire fully automatically. It’s part of what they do. It’s not unconscionable to use this capability when the tactical situation demands it. We discussed a few situations above where it makes sense to use full auto. It’s not a mistake, per se. There are reasons for it. What if 30-50 feral hogs run into your yard within 3-5 minutes while your small kids play?

Think of it like a car. Sure, the engine is designed so that its revs can go all the way up to the red line. But that doesn’t mean we go there every time we get in the car. Imagine if you always kept your car in first or second gear because you love the sound the engine makes at 7,000 RPM. You ought not be surprised when your car handles poorly, drinks fuel inefficiently, and wears out far more quickly.

Hollywood heroes and villains tend to use full auto it as their default response to an enemy threat because it’s cool. Just like it’s cool to pull donuts in your car. Not great for the car, or for the gun. But do our film and TV characters care? Probably not. They find these guns they use them until they either jam or run out of ammo, then they throw them away again.

That’s all for this week. What do you think? Please let me know in the comments below. As always, remember to subscribe if you haven’t already. Thanks again for reading.

Cover picture: Can’t Fire Effectively From Hip: Why Sylvester Stallone’s Gun Technique In $300M Action Movie Wouldn’t Work In Real Life Explained By Expert, TC Philips, Screenrant (Dec 2024)

1. I.e., you squeeze the trigger once and the weapon keeps firing until you release the trigger. Semi-automatic: you need to squeeze and release the trigger for every individual shot. Burst: each trigger squeeze fires a set number of rounds, usually three. ↩︎
2. It’s about 40 kW for a 5.56 mm automatic weapon, which is the more common assault rifle calibre. The 5.56 mm cartridge is much lighter than the 7.62 mm, but its muzzle velocity is appreciably higher and energy scales with the square of velocity, so the difference is less than you might think. ↩︎
3. If you’re tempted to chime in about bump stocks at this point, then I must point out that I’ve never used one. But from what I can tell from watching the experts, they give you a slightly lower rate of fire and much less accuracy than “traditional” full auto. All of which seem like terrible ideas but hey, to each their own. I don’t think we’ll see action heroes using bump stocks any time soon, seeing as their sole purpose is to get around legal restrictions on fully automatic firearms. ↩︎
4. Most weapons have a finite lifespan of rounds so, in theory, every round you put through is doing permanent damage, that’s just how things like physics and entropy work. But the point is that you can really accelerate the process with poor fire discipline. ↩︎