When you think of guns and mud in relation to the AR-15 and AK 47 platforms, do you think that the latter will run no matter what kind of crud you put it through while the former will jam up at the slightest bit of grime?

If so, don’t worry—its a common misconception that goes all the way back to the Vietnam War.

As the good folks from InRangeTV explain in the video above and prove with their patented mud test, the design of the AR-15 actually makes it far more impervious to dirt and mud than the more open design of the AK—even with the dust cover open.

It is true that the AK 47 requires less maintenance than the AR, as in you can run many, many mags through it and beat the crap out of it without it needing a cleaning or maintenance to function. You do have to periodically clean and lube an AR—it simply has tighter tolerances between moving internal parts, whereas the AK simply has more room, and some parts are more fragile.

But, at the same time, the AK has more open gaps and slots where debris can become lodged and sometimes hopelessly jam up the gun. Because of the design, the AR with its comparatively tight tolerances, is far less likely to allow any crud to get into its action in the first place. Fouling from shooting the gun is the chief concern.

“It is the design of the gun that allows it to function (covered in soupy mud). Does this mean the gun doesn’t require more maintenance than an AK? No. What it is is a sealed design that prevents the ingress of filth and dirt into the action and as a result, in conditions like these, supersedes and does better than the AK, which has rather open functionality…”

“You can abuse and AK and have it be reliable. You can’t abuse an AR and have it be reliable, over a duration of time. But if you jump into a mud soup, the AR is more likely to keep running than an AK.”

So why does this reputation often get flipped?

It was an ammo problem, not a rifle design problem, that gave the earliest M16s the jam-o-matic label.

As they explain:

“The issues in Vietnam were completely different. The primary issue in Vietnam was that the military changed the powder specifications between when the gun was tested and when and when it went into its first real issue. This sounds like a minor thing, but by changing the powder specification, they substantially changed the gas pressure at the gas port, which changed the bolt velocity, causing the thing to no longer function reliably.”

Why would the Army do this? Because it had a surplus of one type of propellant and wanted to use it up.

This was compounded by the fact that the military didn’t issue cleaning kits, because at some point along the way the brass got it into their heads that the M16 was somehow self cleaning.

L. James Sullivan, one of the designers of the AR-15 who helped scale down the AR-10 for the 5.56 cartridge for Eugene Stoner, says in the video that “the final report of the congressional investigation was that the way the Army handled that was unbelievable and bordered on criminal negligence. They couldn’t find anyone to blame. I mean, they couldn’t prove that anybody did it deliberately but that’s sure what it looked like. It was sabotaged. And I don’t know how many died because of it.

If you want to see how the AR-15 holds up against sand, see below: