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Offline Nobody's Confidant

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« on: 24/10/2007 17:29:16 »
Why are these are biggest bullet for handheld weapons? It should be easy to make a bigger bullet, you just need a bigger gun!


 

Offline lightarrow

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« Reply #1 on: 24/10/2007 17:43:45 »
Why are these are biggest bullet for handheld weapons? It should be easy to make a bigger bullet, you just need a bigger gun!
Have you ever tried to bring with you ~ 15 Kg of metal in addition to all the other requested equipment for, maybe, some kilometres? I haven't, but I imagine it's not so easy.

It's true that old one-shot black powder rifles had even 0.75 caliber, but they were less heavy because they were much less powerful.
« Last Edit: 24/10/2007 17:46:14 by lightarrow »
 

Offline Nobody's Confidant

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« Reply #2 on: 24/10/2007 17:44:12 »
Riiiiiiiight, good point.
 

Offline DoctorBeaver

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« Reply #3 on: 24/10/2007 17:49:12 »
 

Online Bored chemist

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« Reply #4 on: 24/10/2007 19:29:49 »
"Why are these are biggest bullet for handheld weapons? "
Recoil?
 

Offline lightarrow

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« Reply #5 on: 25/10/2007 12:34:13 »
"Why are these are biggest bullet for handheld weapons? "
Recoil?
Yes, but recoil shouldn't be very high, or much of the bullet's kinetic energy would be lost; to avoid it you have to increase the mass necessarily.
 

Offline i am bored

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« Reply #6 on: 04/11/2007 22:21:51 »
anything larger than 50 caliber you might as well have a small howitzer on your shoulder like a RPG launcher
 

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« Reply #7 on: 04/11/2007 23:11:55 »
Can't see recoil being the limiting factor.  Recoil is a function of the energy of the shot, not its calibre (and even that can be mitigated by using recoilless guns).

The problem with high calibre bullets is aerodynamic - it will lose a lot more energy to drag, and so have a shorter range and less precision, than a bullet of similar mass but smaller calibre.
 

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« Reply #8 on: 05/11/2007 00:25:51 »
some guns direct the recoil downward so the recoil connot be felt if you want a higher caliber handgun even though i would call it a hand cannon it would have to be no smaller than a military issue 50 caliber sniper rifle unles you want a gun with twice the recoil of a desert eagle handgun
 

Offline lightarrow

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« Reply #9 on: 05/11/2007 12:53:58 »
some guns direct the recoil downward so the recoil connot be felt if you want a higher caliber handgun even though i would call it a hand cannon it would have to be no smaller than a military issue 50 caliber sniper rifle unles you want a gun with twice the recoil of a desert eagle handgun

Gun's recoil speed = p/M

p = bullet's momentum = m*v --> m = bullet's mass; v = bullet's speed
M = gun's mass

So, whatever the bullet's momentum p, if the gun's mass M is high enough, the recoil is negligible.
 

Offline lightarrow

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« Reply #10 on: 05/11/2007 13:13:02 »
The problem with high calibre bullets is aerodynamic - it will lose a lot more energy to drag, and so have a shorter range and less precision, than a bullet of similar mass but smaller calibre.
Certainly, but usually higher calibers bullets have greater mass too, with a similar shape; considering for simplicity a bullet of cylindrical shape; if the caliber double, the cylinder diametre and its lenght become 2 times as before, so the bullet's mass becomes 8 times as much.

This means, with the same bullet's speed, an 8-fold momentum, but only a little more of 4-fold air friction (bullet's section is 4-fold) and so a greater range and higher precision, actually.

All this, I repeat, with similar bullet shapes and speeds and of course using a similar gun; you can't do this kind of comparison between, e.g., a 5.56 mm M 16 and a 12.7 mm XVIII century gun.
« Last Edit: 05/11/2007 13:17:07 by lightarrow »
 

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« Reply #11 on: 05/11/2007 13:32:27 »
Certainly, but usually higher calibers bullets have greater mass too, with a similar shape; considering for simplicity a bullet of cylindrical shape; if the caliber double, the cylinder diametre and its lenght become 2 times as before, so the bullet's mass becomes 8 times as much.

This means, with the same bullet's speed, an 8-fold momentum, but only a little more of 4-fold air friction (bullet's section is 4-fold) and so a greater range and higher precision, actually.

All this, I repeat, with similar bullet shapes and speeds and of course using a similar gun; you can't do this kind of comparison between, e.g., a 5.56 mm M 16 and a 12.7 mm XVIII century gun.

Yes, but to maintain the same speed, you need 8 times the charge, and thus manage the commensurate increases in stresses on the gun barrel and other mechanisms.  For a given limit to the stresses a gun can take, an 8 fold increase in mass would need substantial reduction in velocity (but a reduced velocity will still require a slower burning charge).

Nonetheless, if you do want an increase in mass, it is just as easy to design a longer bullet as a thicker one (especially if you are using expanding bullets, but it may be a more complex issue if you are shooting at a hardened target that you want to penetrate without expanding on first contact).
 

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« Reply #12 on: 05/11/2007 17:59:05 »
It must be, ultimately, the energy of the bullet that does the damage. You can get more energy increase for a given momentum increase, if you increase the velocity and keep the same mass of bullet.
this is too complex for us ever to come up with a proper answer. It all depends what you need your bullet to do and how beefy the guy holding the gun is. A good bigun beats a good littleun, usually.
 

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« Reply #13 on: 05/11/2007 19:01:02 »
"So, whatever the bullet's momentum p, if the gun's mass M is high enough, the recoil is negligible."
How far do you want to carry that gun? With a gun of reasonable weight for carrying there's a limit to how much recoil you can take.

There's no question that ship and rail mounted artillery have huge bores and great accuracy. The argument about aerodynamics spoiling things must be mistaken. On the other hand, nobody has to carry them.
Also, as was mentioned, there's not a lot of point after a while since an RPG or some such does the job better.
 

Offline lightarrow

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« Reply #14 on: 05/11/2007 19:51:34 »
Yes, but to maintain the same speed, you need 8 times the charge, and thus manage the commensurate increases in stresses on the gun barrel and other mechanisms.
Not so much, because the barrel inner section and its lenght are greater, so the pressure doesn't need to be much higher; if, to make computations simpler, you have a barrel twice as long, the pressure inside the barrel can be exactly the same to give the same bullet's speed:

F = P*A

F = force on the bullet; P = gas pressure; A = area of inner section

W = F*L

W = work done on the bullet; L = barrel's lenght. So:

W = P*A*L

A is 4-times, L is twice, so, with the same pressure p, W = 8 times, exactly what you need to give the 8-times mass bullet the same speed.
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For a given limit to the stresses a gun can take, an 8 fold increase in mass would need substantial reduction in velocity (but a reduced velocity will still require a slower burning charge).
I think bigger calibers wouldn't have any problem to accelerate bullets to higher speeds than those of smaller calibers, if the weight weren't a problem.
Quote
Nonetheless, if you do want an increase in mass, it is just as easy to design a longer bullet as a thicker one (especially if you are using expanding bullets, but it may be a more complex issue if you are shooting at a hardened target that you want to penetrate without expanding on first contact).
With a smaller caliber the area of the barrel's inner section and so the area of the bullet's section is lower and this means a lower push on the bullet, with the same pressure; it's for this reason that you can't make a bullet much more long than its diametre: you increase the bullet's mass and its friction inside the barrel but not the gas push on it.
« Last Edit: 05/11/2007 19:58:40 by lightarrow »
 

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