Popular Mechanics Claims Astronauts Can Carry M16s on the Moon But Quote Unquote With A Catch

I'm not a consistent reader of Popular Mechanics, but over the years I've read a few interesting stories in their publication. When I saw this piece pop up in my phone feed, the title caught my eye, mainly due to the click-bait title.

Astronauts Really Could Carry M16s on the Moon

This bold claim flies in the face of my understanding of the physics of projectile weapons and how they would operate in space.

My belief is that the editors at Popular Mechanics know this claim is popycock too, and hence the subtitle in fine print

In For All Mankind, U.S. Marines pack heat in space. That could happen in real life, too—with a catch.

The catch being, sure, marines could carry the rifle into space, but they would probably be more successful bludgeoning opponents with it rather than firing it at them.

As mentioned in the story, the moon's low gravity would confound the internal mechanisms for how rounds are fed into the chamber from the magazine:

Gravity would affect all aspects of the M16, from how bullets are seated in the magazine to how the buffer spring would bounce the bolt carrier group back and forth inside the weapon. The internal action of the M16 is precisely timed, and a change in gravity would throw everything off.

Changing the mass of various internal parts, spring weights, and even the type and amount of gunpowder used might make a lunar M16 workable—but it would require a lot of testing under lunar conditions. One concern: The M16 uses gunpowder gases to cycle the weapon. Just how would that hot, pressurized gunpowder gas behave in low gravity?

Note the presence of the big qualifier "might" (my emphasis).

The story also points out the ballistic challenges for coping with the different trajectory rounds travel on the moon.

Bullets in principle should work fine, since they use their own propellant and don’t rely on oxygen. But again, the big issue here would be gravity.

Under Earth gravity, an M16 bullet starts a slow, inexorable drop as soon as it exits the barrel, one that eventually ends up with the bullet plowing into the ground. Earth’s gravitational influence means a terrestrial M16 bullet will drop 24 inches at 400 yards. While a bullet fired under lunar gravity would still eventually plow into the lunar soil, at one-sixth gravity, the same bullet would fly a flatter, steadier trajectory for far longer.

I guess as long as you site your new shiny moonbat white M16 in on the lunar range, you might have slightly better accuracy with it?

One aspect that I found strangely absent from the story was recoil. This is a very frequently explained subject in your standard space opera/sci-fi novel for why . There just so happens to be this pesky property observed by some guy named Sir Isaac Newton:

Every action has an equal and opposite reaction

Newton's Third Law says that firing high-velocity rounds will enact an opposing force on the rifle, and this force will be transferred into the person holding it. On Earth, with the aid of its gravity, we can anchor ourselves on Terra Firma and absorb the recoil from the opposing force on the riffle by the ejection of the bullet. With 1/6 of the Earth's gravity, the same proposition on the Moon will not only render your fire inaccurate, but has a good chance of both launching the astronaut backwards and applying random spin/rotation of the astronaut depending on how they hold/aim the weapon. I don't know, but I would think it best not to perform slow-motion gymnastics while operating a rifle in combat.

One other oddity I noticed in the story is that the author consistently referred to the modern variant of the M-16 rifle (A2) as a candidate for use in space, but then included a stock photo in the story of a soldier in the Vietnam era (photo caption stating "A U.S. soldier with the 1st Cavalry Division on patrol, Vietnam, 1971.") carrying an M-16. I'll defer to other more knowledgeable commenters, but what I learned in the Army is that the M-16A2 riffle was developed after the Vietnam war based on experiences and findings from use of the first generation of M-16 in that conflict (a big learning being that full auto mode led to poor fire control and increased rate of weapon jams). So in all likelihood the soldier in that photo is not carrying an M-16A2 riffle.

So in summary: the click-baity title is factually true I suppose, astronauts could lug around the M16A2 rifle on the Moon, but the internal mechanics would likely not operate correctly, the sighting as developed/tested terrestrially would not be accurate, and there would be this small problem of launching astronauts about every which way when they fired the weapon.

I guess I had a higher opinion of the writing in something like Popular Mechanics, which has been around seemingly forever and has (IMHO) had a fairly high standard of content that they put in their publication. Again, I have only been an infrequent reader, though, and I tended to leaf through it in paper form while waiting for appointments in an earlier age, long ago before the InterWebz. Maybe this is simply the new norm or new bar that has been set for the field of "journalism" moving forward.

Who thinks Marines in space would be limited to a firearm to use as a weapon?
I have a feeling we have crossed over to better things.

Even so, I am not convinced that a standard M-16 would not function in 1/6 gravity.

I think the author was confused about his physics. Even in Earth's gravity, the firearm pushes back when fired. The mass of the firearm is much greater than the bullet, so the bullet goes much faster from the same push than the firearm does.

Read through that makes me think the author knows next to nothing about guns, and m16's in particular.

If gravity played a role in how rounds seat in a magazine, and enter the chamber, the gun wouldnt fire if you held it upside down here on earth.

Is the author confusing m16's with gravity fed bb guns?

I don't realy see a problem with the operation of the mechanism. The problem is going to be overcoming the recoil and Moon dust. The moon dust in sharp like sandblasting media as there is no wind on the Moon to wear off the sharp corners. It is all made during impacts and will be as sharp as the material comoing out of a rock grinder. It also gets into everything and was eating the Apollo spacesuits after only their short exposure to the dust.

I don't think any firearm designed for use on earth would survive use on the Moon for over a few hundred rounds without needing to be replaced due to worn out moving parts.

If you want a Moon rifle, I would think a compressed gas powered, bolt action, with a recoil suppression mechanism would be better.

Also, would regular ammunition spontaneously detonate in 100% oxygen atmosphere?

Now Mars has fine round dust and more gravity. I can see a m16 working with only reducing the powder to reduce recoil and adjust the gas operating system to compensate for the lower operating pressure.

I think a shotgun, possibly 410 with bird shot, would be better in any ship or shelter because it would do less collateral damage to what ever is behind the target. Anything you punch a hole in you will need to fix.

originally posted by: butcherguy
Who thinks Marines in space would be limited to a firearm to use as a weapon?
I have a feeling we have crossed over to better things.

Even so, I am not convinced that a standard M-16 would not function in 1/6 gravity.

I think the author was confused about his physics. Even in Earth's gravity, the firearm pushes back when fired. The mass of the firearm is much greater than the bullet, so the bullet goes much faster from the same push than the firearm does.

It would be a small thing to down load the cartridge, port the barrel, and add mass to the rifle. I would be more concerned about the intense changes in temperature affecting both the primer and propellant.

originally posted by: Nickn3

originally posted by: butcherguy
Who thinks Marines in space would be limited to a firearm to use as a weapon?
I have a feeling we have crossed over to better things.

Even so, I am not convinced that a standard M-16 would not function in 1/6 gravity.

I think the author was confused about his physics. Even in Earth's gravity, the firearm pushes back when fired. The mass of the firearm is much greater than the bullet, so the bullet goes much faster from the same push than the firearm does.

It would be a small thing to down load the cartridge, port the barrel, and add mass to the rifle. I would be more concerned about the intense changes in temperature affecting both the primer and propellant.

It does get awfully hot AND cold on the Moon. Good point!

I would agree that using a compressed gas rifle would likely be a better choice, with the lack of atmosphere and much less gravity the round wouldnt need to be moved with as much initial velocity since the projectile wont slow down as fast. It will retain it initial velocity or close to it much much longer.

Also, you dont neccesarily need to cause massive trauma to your opponent to incapacitate him, you really just need to puncture or rip his space suit.

A sharp pellet, or some type of flechette would probably work very well.

a reply to: SleeperHasAwakened

Hmmm...me thinks the author is a little misinformed on several issues. However, it is an interesting question to ponder!

I guess my first question though would be...why would an astronaut on the Moon need an M-16???

a reply to: Flyingclaydisk

For the same reason everyone needs an m16. Their awesome as hell.

Indeed, gravity doesnt change the mass of anything either. It's full of bogus claims.

There is a catch tho. No atmosphere means evaporation of any lubricant and also cold welding of internal parts. I knew I've seen it before. Here's the vid explaining everything.

originally posted by: Flyingclaydisk
a reply to: SleeperHasAwakened

Hmmm...me thinks the author is a little misinformed on several issues. However, it is an interesting question to ponder!

I guess my first question though would be...why would an astronaut on the Moon need an M-16???

Propulsion.

If you get tired of hopping you can fire it into the ground at a 45 degree angle it would give you a nice little jump. Like a mini short burst rocket pack.

a reply to: SleeperHasAwakened

Saw this last week.. I got a laugh.


S&F😊

originally posted by: caterpillage
Read through that makes me think the author knows next to nothing about guns, and m16's in particular.

If gravity played a role in how rounds seat in a magazine, and enter the chamber, the gun wouldnt fire if you held it upside down here on earth.

Is the author confusing m16's with gravity fed bb guns?

I was thinking the same exact thing 😂😅🤔🤣

a reply to: SleeperHasAwakened

An m16 could indeed fire but it wouldnt last long. The lunar dust will kill it rather quickly unless they took steps to prevent that which i couldnt even imagine how. The other problem is the heat the rifle is air cooled on the moon that would present a huge problem you would need at the minimum change it over to liquid cooled. Using a crossbow would be more effective however but for a limited engagement the rifle would fire at most 2 clips before becomng to hot and warping the barrel.They could bring back the rocket gun it didnt go over well here on earth but on the moon should work just fine. As far as the author they are just wrong the springs would work just fine. the cartridge would fire and it would be ejected.

I remember reading an old science fiction story about a battle on the Moon. The battle had happened months ago, but, at certain times the characters would have to seek cover because the rounds fired in that battle were in a low orbit around the Moon. I really don't think dust would be a factor, because there's no air for it to be suspended in. I can see the issue with the suits because they are in contact with the surface.

I can see that there will need to be changes in the amount of powder loaded in the rounds. With no friction from air the muzzle velocity will increase. Another problem is that the recoil springs might need changed. When the gasses bleed into the gas tube, usually there is air in the tube. The gasses heat that air and it aids in the reloading system.

originally posted by: caterpillage
I would agree that using a compressed gas rifle would likely be a better choice, with the lack of atmosphere and much less gravity the round wouldnt need to be moved with as much initial velocity since the projectile wont slow down as fast. It will retain it initial velocity or close to it much much longer.

Also, you dont neccesarily need to cause massive trauma to your opponent to incapacitate him, you really just need to puncture or rip his space suit.

A sharp pellet, or some type of flechette would probably work very well.

Good points.

One fixture of sci-fi space novels are railguns, which can continue to function without needing to lug around propellant canisters or powder-packed cartridges; you just need ammunition and a continuous energy supply to recharge batteries powering your magnets, and that shouldn't be a problem unless you're someplace the Sol don't shine

IMHO the science and tech consultants for the series referred to in the P.M. article ("For All Mankind") didn't do a very good job advising the producers of the show. Yeah yeah, this is a "re-imagined history" plot set in the 1980s, but is it plausible that any sustained settlement would be established on the Moon, sufficient tech would be developed to move gear there and colonize the place, military conflicts would ensue .... and the best weaponry to bring to bear would be white spray-painted M-16A2 with different firing components and optics? No railguns? No radiant weapons?

o_O

Meh, I'll stick to my Peter Hamilton and Greg Baer books.

originally posted by: Flyingclaydisk
a reply to: SleeperHasAwakened

Hmmm...me thinks the author is a little misinformed on several issues. However, it is an interesting question to ponder!

I guess my first question though would be...why would an astronaut on the Moon need an M-16???

The P.M. story was a puff piece, more or less, on the curious weapon choices for some new TV program called "For All Mankind" about the US/Soviet space race in some parallel universe where USSR reached the Moon first.

a reply to: JIMC5499

The rounds would not go into orbit they would just travel further on the moon. Lets say on earth a bullet travels 1000 meters on the moon it would trave 6000 meters, Lower gravity means the bullet woould take longer to hit the ground.

They didn't show them actually hitting anything yet, so guessing that might end up being part of the plot to come.

The recoil of a M16 is so low that you can put it against your jaw and fire a round without even a bruise.

I used a m16 in Vietnam and own a AR15.

I have done the AR15 trick of firing it with the butt against my jaw many times while training people that were afraid of the recoil.

Lubing the M16 for use in space would be no problem as there are many dry lubes on the market that would not off gas.

The only problem i can see would be firing in full auto as that would act like a jetpack.

a better weapon for use in space or on the moon would be a 22lr type pistol as you only need to put a couple holes in the other guys suit to give him major problems