Let's let Professor John Rambo explain the theoretical physics of machine gunnery in this scene from First Blood Part II:
The theory goes like this: You pull the trigger on a machine gun until the whole world turns into blood, and it is awesome. You can't argue with that; that's science.
After the first minute or so, provided that he had enough ammo to fire that long in the first place, Dr. John Rambo would find his monstrous murderection completely flaccid.
See, machine guns are designed more for brief covering fire and the occasional, precisely delivered packet of death. The M60 of Rambo fame up there can survive sustained fire at 100 rounds per minute. Which is awesome. But afterward, it will require breaking apart and changing the whole goddamn barrel. Yes, you read that correctly: Machine gunners have about a solid minute of constant ass-kicking, but afterward, they have to stop, break apart the machine gun and align and insert a brand new replacement barrel before continuing to be rad for precisely one more minute. And they do all this while in a combat zone. Under enemy fire. In the middle of a war zone.
It's not just Rambo's antiquated Vietnam vengeance equipment, either: The modern stuff doesn't work much better. Turns out that no amount of money can cool a 22-inch steel pipe fast enough to compensate for the hundreds of tiny explosions per minute happening inside of it. The M249 that replaced the M60 has a sustained fire rate close to Rambo's preferred power band (750 to 800 rounds per minute), provided that you change the barrels every, wait for it: Yep, every minute.
"And that's why we use handguns when hunting in the city. Much less downtime."
That's the longest a bitchin' machine gun fight could ever last in reality until everybody involved had to stop, pull out their iPhones and order up some new parts.
All is quiet on the bridge. A dozen submariners tensely but silently go about their business. Suddenly, a deafening ping rings out through the hull. An enemy sub has spotted you! Take evasive maneuvers! Call Sean Connery -- if nothing else, his dulcet tones will soothe your frazzled nerves in the deadly game of hide and seek to follow.
Most people are aware that subs use sonar to "see" underwater. But here's what you probably think a sonar screen looks like:
Followed by blips that look like little spaceships and a confused operator saying "There are six of them ... no, wait, 12. Now 20!"
Pretty simple, right? You're in the middle and the other guy has the decency to be a bright purple dot, so he's easy to spot. You tell the torpedo dude to, like, point at the dot and pull the trigger, and then boom -- no more dot. But here's what an actual sonar screen looks like:
"So the squiggly lines finally made their move. This war just got interesting."
It looks like 1989 needs a price check on something. How do you fight using that?
Well, there are two main types of sonar: active and passive. Active is closer to what you normally associate with sonar -- subs send out a loud "ping" and then time how long it takes to get back to them. While active sonar will give you a lot of useful information, like bearing, range and speed, it also has the drawback of giving away your position to anyone listening within a several-mile radius.
What subs use 99 percent of the time is passive sonar, which basically boils down to a bunch of highly sensitive microphones stuck in the water and people listening really, really hard. This type of sonar delivers way more useful information, such as the type and class of ship, even identifying specific individual ships in some cases, just by the sound. Since passive sonar is picking up emitted sound instead of reflected sound, range could be quite complicated to calculate. Back during the war movie days, even with a computer assisting, it could take up to 15 minutes of uninterrupted listening to get an accurate enough estimate to fire a torpedo, and that's only if the submarine in question was polite enough to not change speed or direction at all while it was being hunted. If it was one of those rude submarines (probably a Russian; those boorish Russkies just up and abandon the rules of high society the very second you try to kill them) that stops or dives below a thermocline layer, you lose track of them completely and it's back to square one.
"Fuck this, I'm just gonna go look. Cover me."
So it turns out that Hollywood has been lying to you about what warfare actually looks like, because for the most part, it's like teenage sex: There's all sorts of tense build-up, but the payoff is usually ungainly and awkward, and it's all over way too fast.
Robert Evans manages the article captions and the workshop moderators here at Cracked. He also writes a travel column for Vagabondish -- you can reach him here. When he's not making blind people play dodgeball, Chris writes for his website and tweets. You can email him at firstname.lastname@example.org.
For more things Hollywood is horribly wrong about, check out 6 Lifesaving Techniques From the Movies (That Can Kill You) and 5 Things Hollywood Thinks Computers Can Do.
If you're pressed for time and just looking for a quick fix, then check out 4 Hilariously Passive-Aggressive Ways People Paid Fines.