Physics of A Firearm of Unusual Size

[Lanodantheon]

Writing a short story involving a 185ft Giant using an appropriately sized Dragonuv Sniper Rifle for vermin shootin'.


You can guess what kind....


But, I also wanted to know more about this normally cartoony situation. SO I found I had to use... *Dramatic swell*....MAAAATH.....*Orchestra Hit*....


Unfortunately, I'm not so good with physics and I just wanted to know more about the logistics of this situation from somebody who knows more than me. Hopefully somebody lurking this forum will know something and have a TI-83 handy.


Note: For reference I used a 2 inch tall ninja(5'5" in life) I have on my desk as reference compared to my 5'8" giant. And this assumes an appropriately scaled gun and full-metal jacket bullets. Assume he got the Dragonuv online at the giant supply store(he did actually now that I think of it).


1. How tall is the giant using my aforementioned scale? My initial calculation came to about 185ft tall give or take. 


2. How big would the bullets be, i.e. could a human sized person carry one? I already calculated a 7.62x56mm round scaled up to about a foot in diameter and 6 ft long but I don't know how much that would weigh.


3. Physics doesn't scale well against gravity and having 34 times the gunpowder does not mean that 34 times as much force will be imparted. How good would the muzzle velocity actually be assuming gunpowder? If he misses the bullets will rip through things, I'd just like to know how far it'll go until it stops and what will happen tot he ground it hits.


4. Assuming the scaled up bullets actually work(I don't want to handwave it but I can with Magic), how loud would the shots be? If it's loud enough, the heroes holding onto the giant may not need to worry about getting stepped on after being violently deafened by the sonic boom.

[Aminar]

I would assume that your going to need to BS/fudge some of the physics anyway, as the materials a normal gun is made of wouldn't hold up well to that kind of abuse.  Maybe having it use a special form of gunpowder that is giant mixed and some explosion proofing of mythic proportions or the like. 

Basically literary fudging versus working the numbers out perfectly.

[Haru]

1. How tall is the giant using my aforementioned scale? My initial calculation came to about 185ft tall give or take. 

That's about what I got, too.

2. How big would the bullets be, i.e. could a human sized person carry one? I already calculated a 7.62x56mm round scaled up to about a foot in diameter and 6 ft long but I don't know how much that would weigh.

The calculations for the size seem about right.
That would amount to about a ton (1000 kilograms) for 1 round. Kind of seems like overkill
The calculation:
m=V*d
m = mass
V = volume
d = density (which for steel is 7.85 g/cm³)

I approximated the form of the bullet as a simple cylinder, which will be enough to ballpark a weight. The volume is then:
V=r²*PI*l
r = radius (1/2 foot in your case)
l = length (6 feet)

3. Physics doesn't scale well against gravity and having 34 times the gunpowder does not mean that 34 times as much force will be imparted. How good would the muzzle velocity actually be assuming gunpowder? If he misses the bullets will rip through things, I'd just like to know how far it'll go until it stops and what will happen tot he ground it hits.

Actually, gravity is part of the whole physics thing. If you can get your ton of bullet up to the speed of a regular bullet, it would be affected by gravity like any normal bullet would. The only thing it would have to deal with would be greater aerodynamic resistance from the increased surface.

The formula here is:
F=m*a
F = Force
m = mass
a = acceleration

or the other way around:

a=F/m

which means, if you have double the mass, you need double the force to get it to an equal speed. I estimated the weight of the small bullet from your numbers above to about 20grams, which would mean you would need 50,000 times the force of a regular load to get the same result.

4. Assuming the scaled up bullets actually work(I don't want to handwave it but I can with Magic), how loud would the shots be? If it's loud enough, the heroes holding onto the giant may not need to worry about getting stepped on after being violently deafened by the sonic boom.

I am not sure how much propellant you need to shoot a normal bullet, if you find out, multiply it by 50,000 and you will have an enormous pile of explosive material lying around. It might or might not be enough, but it is a good estimate, I think. I don't think it would create a sonic boom, because that would only happen if the bullet passed the sound barrier. The explosion would be loud, but manageable, I think.

Hope I could help so far.

[Breandan]

It would, for simplicity's sake, be a rifle firing the shells used in US naval battleships, more or less. So, research those and you'll have an idea of what you are dealing with. Now, that being said... why in the nineteen flaming hells of tap-dancing China is he using THAT against people? Squish em, throw stuff at them, or simply roll gigantic rocks around on them. Much more effective

[Aminar]

It would, for simplicity's sake, be a rifle firing the shells used in US naval battleships, more or less. So, research those and you'll have an idea of what you are dealing with. Now, that being said... why in the nineteen flaming hells of tap-dancing China is he using THAT against people? Squish em, throw stuff at them, or simply roll gigantic rocks around on them. Much more effective

On that point, at this size solid chunks of metal cause explosions(frag ones at least) on impact, are you taking that into account? Because using it as a varmint rifle seems silly when he leaves craters as big as his feet after every shot and obliterates elephants.
That said-Written well I can see this being pretty damned cool.

[Enjorous]

It would, for simplicity's sake, be a rifle firing the shells used in US naval battleships, more or less. So, research those and you'll have an idea of what you are dealing with. Now, that being said... why in the nineteen flaming hells of tap-dancing China is he using THAT against people? Squish em, throw stuff at them, or simply roll gigantic rocks around on them. Much more effective

Because this requires standing up and running around and them humans is quick! With his shootin' gun he can sit on his porch and shoot 'em all day long!

[Lanodantheon]

Thanks Haru. I'll need to do more.....Math... but now I can make more headway.

I would assume that your going to need to BS/fudge some of the physics anyway, as the materials a normal gun is made of wouldn't hold up well to that kind of abuse.  Maybe having it use a special form of gunpowder that is giant mixed and some explosion proofing of mythic proportions or the like. 

Basically literary fudging versus working the numbers out perfectly.

Definitely. One of the first things that occured to me . It's effectively invulnerable or otherwise enchanted because there's Magi-Tech.

It would, for simplicity's sake, be a rifle firing the shells used in US naval battleships, more or less. So, research those and you'll have an idea of what you are dealing with.

Will do. Thanks.

Now, that being said... why in the nineteen flaming hells of tap-dancing China is he using THAT against people? Squish em, throw stuff at them, or simply roll gigantic rocks around on them. Much more effective

For the sake of clarity (and to give a good laugh), I will explain. Note: Magi-Tech World that probably should have given up a few apocalypses back AND it's a comedy.
 
The Giant was cooking breakfast that morning: Bacon & Ham from the meat processing vat he thugged together(Vat grown meat is similar to pork so I assume it could make bacon), Pancakes and an omlete using eggs from his Chickens of Unusual Size when he got attacked by a group of "Grubs".


The Giant normally uses the gun against....big things, but then the grubs' Rocket launcher broke open the pen for the Chickens and the Grubs were using Magical shields to protect themselves. so the giant got all pi%#ed. They obviously weren't scared of the giant since they were still shooting at him and those RPGs hurt so the giant pulled out the gun and started shooting.


A bunch of small critters ruin your breakfast and start wrecking your home. What would you do? 


Meta-story though, the gun needs to be present int he story for the novel that follows many years after the events with the giant.  but I've said too much.    

On that point, at this size solid chunks of metal cause explosions(frag ones at least) on impact, are you taking that into account? Because using it as a varmint rifle seems silly when he leaves craters as big as his feet after every shot and obliterates elephants.
That said-Written well I can see this being pretty damned cool.

Though now that I think of it, if he had a dedicated anti-grub weapon it'd probably be a shotgun of unusual size. I cringe at that thought now... It would probably look like those Flechette sheet launcher things the Army's was testing for deployment. I can't remember if they finished or scrapped those things.


Well, food for thought.   

[Aminar]

Oh dear.  Terror shotgun.

[the neurovore of Zur-En-Aargh]

Just picture me rolling on the floor moaning feebly about materials science and square-cube laws, here...

[Figging Mint]

Just picture me rolling on the floor moaning feebly about materials science and square-cube laws, here...

185ft Giant with REALLY REALLY good orthopedic support.   

[Lanodantheon]

185ft Giant with REALLY REALLY good orthopedic support.   

Just picture me rolling on the floor moaning feebly about materials science and square-cube laws, here...

If it makes you feel any better, the giant's not necessarily made entirely of normal flesh and bone anymore. His body got converted into a Magi-Tech Elemental Titan...thingie some centuries before the story begins.


The world this takes place in was specifically constructed so that no matter how ludicrus the way an idea violates physics I can write it off as either, "Magic, your argument is invalid..", "Super technology handles that like this..." or "Magi-Tech, your argument is invalid".

[the neurovore of Zur-En-Aargh]

The world this takes place in was specifically constructed so that no matter how ludicrus the way an idea violates physics I can write it off as either, "Magic, your argument is invalid..", "Super technology handles that like this..." or "Magi-Tech, your argument is invalid".

I wish you success of it, but I suspect that a book written consciously from that philosophy will not, alas, be something I could enjoy reading.

[Lanodantheon]

I wish you success of it, but I suspect that a book written consciously from that philosophy will not, alas, be something I could enjoy reading.

Thanks for the wish of luck. I will though continue to research and try to see what else can be done so that even the absurd can be not so far fetched.

[Aminar]

I wish you success of it, but I suspect that a book written consciously from that philosophy will not, alas, be something I could enjoy reading.

I think this would work best as a humorous story, then I can see enjoying it-given that his premise reminds me of Xanth.

[the neurovore of Zur-En-Aargh]

I think this would work best as a humorous story, then I can see enjoying it-given that his premise reminds me of Xanth.

Xanth is beyond "does not work for me" into "gives me hives", fwiw.