Modern sporting rifles on the Moon?

[madmas1208]

My son was using his Playstation this morning and I noticed an ad for a television series called "For all Mankind" and I was wondering how effective an AR/M4 style rifle would be on the Moon?

(Disclaimer: its mostly tongue and cheek and I am aware its Hollywood fiction)

 

[weekendracer]

NASA did a study on such things back in the day. Without looking it up, I seem to remember the gun 'should' fire.

I'd assume then that they'd be relatively effective since all you need to do is puncture the suit and get behind cover and let physics kill the other person.

again, easier than I thought it would be, Cornell article on the subject:

Can you fire a gun on the Moon? (Intermediate) - Curious About Astronomy? Ask an Astronomer

Ask an Astronomer is run by volunteers in the Astronomy Department at Cornell University. We answer your astronomy questions. Please browse our archive first.

curious.astro.cornell.edu

 

[Picton]

Range would increase, presumably. The Moon only has 1/6 the gravity of the earth, so for any given range at which you could expect gravity to contribute to bullet drop here on earth, just multiply by six to get the moon distance.

Of course, everyone knows an AK would be a better choice as a space weapon (and everywhere else). I don't have the knowledge to tell you what reduced gravity and/or lack of oxygen would do to the gases in a direct-impingement system, but I'd imagine a piston would be more reliable. A bolt-action is probably even better.

 

[Mesatchornug]

Range would increase, presumably. The Moon only has 1/6 the gravity of the earth, so for any given range at which you could expect gravity to contribute to bullet drop here on earth, just multiply by six to get to the moon.

Of course, everyone knows an AK would be a better choice as a space weapon (and everywhere else). I don't have the knowledge to tell you what reduced gravity and/or lack of oxygen would do to the gases in a direct-impingement system, but I'd imagine a piston would be more reliable. A bolt-action is probably even better.

DI is still scavenging gas from the firing cycle so it should be fine. That said, yes a bolt should be more reliable.

 

[Rocky Mosasaurus]

Yes, like Picton pointed out there would be less bullet drop because the smaller value of g, on earth 9.81 m/s^2, on the moon 1.625 m/s^2.

 

[cams]

Yes, like Picton pointed out there would be less bullet drop because the smaller value of g, on earth 9.81 m/s^2, on the moon 1.625 m/s^2.

English please so semi retarded folks like me can still follow along too.

 

[Mesatchornug]

If they'd done their research, they'd use these:

Gyrojet - Wikipedia

en.m.wikipedia.org

 

[Mesatchornug]

Yes, like Picton pointed out there would be less bullet drop because the smaller value of g, on earth 9.81 m/s^2, on the moon 1.625 m/s^2.

The interesting question is how the decreased drag affects things like drift, etc.

 

[SKumar]

I wonder how the gas system would work in outer space?

 

[Rockrivr1]

Wouldn’t think there would be enough oxygen for much of the powder to burn. Sorts of like a squib round firing. Not sure how much velocity that round would get.

 

[Mesatchornug]

Wouldn’t think there would be enough oxygen for much of the powder to burn. Sorts of like a squib round firing. Not sure how much velocity that round would get.

The oxygen is provided by the powder. It's a sealed system.

 

[Rocky Mosasaurus]

English please so semi retarded folks like me can still follow along too.

Any weight a person has on earth can be calculated with the formula Weight = mass * value of gravity. Well your mass will stay the same on these different planets but the value of gravity will change which implies your weight will change on said planet. So calculations to bullet drop will be changed since the weight has also changed in the necessary formulas.

 

[Mesatchornug]

I wonder how the gas system would work in outer space?

Gas systems are mostly sealed. The cartridge provides the gas.

There's less back pressure against the cartridge, so there'll be less uncorking pressure, but that should be minimal

 

[Picton]

Wouldn’t think there would be enough oxygen for much of the powder to burn. Sorts of like a squib round firing. Not sure how much velocity that round would get.

I THINK the powder would get a pretty good ignition, since the cartridge is a closed system during most of the time the bullet is traveling down the barrel? So as long as the cases were loaded on Earth, each one would carry its own O2 with it?

It's an interesting set of questions.

 

[Mesatchornug]

I THINK the powder would get a pretty good ignition, since the cartridge is a closed system during most of the time the bullet is traveling down the barrel? So as long as the cases were loaded on Earth, each one would carry its own O2 with it?

It's an interesting set of questions.

A simple, commonly cited, chemical equation for the combustion of black powder is: 2 KNO3 + S + 3 C → K2S + N2 + 3 CO2.

It's all inside the case. Even loaded in vacuum would still work.

Hooray solid oxidizing fuel!

 

[Mesatchornug]

Shooting under water has the same questions to answer but under greater pressure...

View: https://youtu.be/cp5gdUHFGIQ

 

[Rocky Mosasaurus]

Shooting under water has the same questions to answer but under greater pressure...

View: https://youtu.be/cp5gdUHFGIQ

Yes, a common misconception is that guns wouldn’t function underwater. While drag forces would greatly affect range, some guns most certainly would be able to function with greatly reduced muzzle energy. But with increasing depths and increased pressure I am sure the gas systems of most firearms would be disrupted sufficiently to render operation impossible.

 

[Rocky Mosasaurus]

APS underwater rifle - Wikipedia

en.m.wikipedia.org

 

[Mesatchornug]

Yes, a common misconception is that guns wouldn’t function underwater. While drag forces would greatly affect range, some guns most certainly would be able to function with greatly reduced muzzle energy. But with increasing depths and increased pressure I am sure the gas systems of most firearms would be disrupted sufficiently to render operation impossible.

Go deep enough and all you'll get are squibs

 

[Rocky Mosasaurus]

Obligatory most epic underwater battle scene:


View: https://m.youtube.com/watch?v=Z3my3VW6vXw

 

[Wrench75]

English please so semi retarded folks like me can still follow along too.

Read this in Captain Caveman voice. "Less gravity pull'um down. Bullet go more far. um!"

The rest of y'all seem to be ignoring the cold. Mechanically speaking an AR should be able to function. But tight tolerances get a whole lot tighter at something like -400 deg. How much did the bore decrease? Did the bullet diameter decrease by the same amount, or KABOOM!! Will the spring steel in the mag spring still spring? Or is it so stiff now that you only get the one chambered round? I'd be the cold would be the biggest factor at play.

One thing that always makes me laugh is the scene in Firefly where Jane puts one of his rifles into a spacesuit when he needs to shoot it outside the ship.

 

[DecOFlaherty]

You guys are all thinking about gravity, oxygen and atmospheric pressure.

My first thought is, "how am I going to get my fat space suit finger in the trigger guard?

 

[EC1]

I expect that the distance traveled would exceed the proportional difference due to differing gravites as there would be zero wind resistance and no drag.

 

[whacko]

The oxygen is provided by the powder. It's a sealed system.

Yup. Same reason they will fire under water.

 

[Broc]

NASA did a study on such things back in the day. Without looking it up, I seem to remember the gun 'should' fire.

I'd assume then that they'd be relatively effective since all you need to do is puncture the suit and get behind cover and let physics kill the other person.

again, easier than I thought it would be, Cornell article on the subject:

Can you fire a gun on the Moon? (Intermediate) - Curious About Astronomy? Ask an Astronomer

Ask an Astronomer is run by volunteers in the Astronomy Department at Cornell University. We answer your astronomy questions. Please browse our archive first.

curious.astro.cornell.edu

The gun will fire, the reaction doesn't need oxygen. The bullet wouldn't drop and probably wouldnt lose speed (if not on the moon), or it would lose little speed due to weaker gravity (assuming standing on the moon). It would also shoot very flat, also due to weaker gravity.

 

[Broc]

English please so semi retarded folks like me can still follow along too.

Bullet flies straighter.

 

[Broc]

A simple, commonly cited, chemical equation for the combustion of black powder is: 2 KNO3 + S + 3 C → K2S + N2 + 3 CO2.

It's all inside the case. Even loaded in vacuum would still work.

Hooray solid oxidizing fuel!

While I agree the reaction doesn't need oxygen, modern ammo for AR/AK uses smokeless, not black powder.

 

[Mesatchornug]

While I agree the reaction doesn't need oxygen, modern ammo for AR/AK uses smokeless, not black powder.

Of course. I was too lazy to get the formula for smokeless. I should've linked to the wiki article it comes from.

 

[Saltydog]

Point is moot. China will claim the Moon after they land and occupy it sometime during Slow Joe's reign after he cancels the US Space Force. AK's all around.

 

[HorizontalHunter]

The real question is ”What will a pre-Biden AR cost on the moon?”
Will it have out of this world pricing?

Bob