Something I always wondered about...

[nestork]

There's been a lot of talk about guns in here lately, and there's something I've always wondered about...

I don't know how far a regular pistol or rifle will shoot, but this web site about the battleship USS Missouri (which is the one that McArther accepted the Japanese surrender on at the end of WWII)

states as follows:

"Missouri's main battery consisted of nine 16 in (406 mm)/50 cal Mark 7 guns, which could fire 2,700 lb (1,200 kg) armor-piercing shells some 20 mi (32.2 km)."

20 miles! Geez. Obviously, that's a lot farther than any rifle or pistol will shoot.

Is that because:

a) the gunpowder used in those cannons is more powerful than the stuff used in regular bullets,

b) or is it because the battleship's cannons are pointed upward to maximize range,

c) or is it that the cannon's barrel is longer so the power in the explosion acts on the projectile for a longer period of time, thereby accelerating the shell more than a bullet

d) or something else entirely.

It just strikes me as odd. I'm thinking that the ratio of lengths between a bullet in a rifle barrel and a shell in a cannon barrel would probably be pretty similar. So, what accounts for the cannon having 20 times the range? Is it just that the gunpowder used in the cannon is 20 times as powerful as than that used in bullets, or is it that the shell stays in it's barrel 20 times longer than a bullet and therefore receives 20 times as much of a push?

[Attila Iskander]

ALL of a), b), c) and more More powder is used, higher pressures are achieved

I think you need to re-shape your question to make it obvious The amount of pressure you build behind the projectile defines the amount of force exerted on it. The weight of the projectile affects how much resistance to acceleration the projectile has The length of the barrel affects how long that force is applied The weight of the projectile affects how long that force is applied to it.

It's a dynamic equation that allows for creative adjustment of how big, how heavy both the gun and the projectile can be and will be.

[Jim Elbrecht]

All of the above-- I was on an mountain along the coast of Vietnam in

1. Naval Gunfire used to go overhead on its way to the highlands. holy crap! Never had the pleasure of seeing one up close-- but the projectile supposedly weighed in similar to a Volkswagen [bug? van?]

20 miles is pretty good-- but the German long guns of WWI could shoot as far as 75 miles-- Google the 'Paris Gun'.

Jim

[dadiOH]

Somewhere between a mile and a 3 1/2 miles.

[Doug Miller]

nestork wrote in news:nestork.b187e08 @diybanter.com:

A *lot* farther than you think it will. :-) Read on.

No, it isn't.

No. It is more powerful, but that's not the reason for the extremely long range.

Yes -- but if you do the same thing with a rifle, you'll get the same result: greatly increased range, compared to firing it with the barrel horizontal.

No. The muzzle velocity on those guns is in the neighborhood of 800 m/s, which is actually

15-20% *lower* than that of many common hunting rounds (e.g. typical muzzle velocity for a 30-.06 is around 880 m/s).

Yes -- because the battleship shells are so large, they are less affected by air resistance than are rifle bullets. I have a .243 rifle which fires an 85-grain round at a muzzle velocity of about 1000m/s. A quick back-of-the-envelope calculation shows that -- in the absence of air resistance -- if the barrel is elevated at an angle of 45 degrees, the bullet will travel over 100 kilometers before striking the ground. Obviously that won't happen, because it

*is* subject to air resistance. While the battleship shell is subject to the same air resistance forces as the bullet, the magnitude of those forces in proportion to a 1200-kilogram shell is obviously much smaller than in proportion to a 6-gram bullet, and hence their effect on the trajectory of the shell is correspondingly much smaller.

No, actually, it's not -- the ratio is a *lot* *higher* for a typical hunting rifle than it is for those cannons.

With an 800-inch barrel and a 64-inch projectile, the cannons have a ratio similar to that of most *pistols*.

It *doesn't* have "20 times the range." What makes you think that a rifle can shoot only one mile?

It's not.

It doesn't.

It doesn't.

It's all about angle of elevation, and the fact that battleship shells weigh two hundred thousand times as much as rifle bullets and consequently aren't affected nearly as much by air resistance.

[Tony Hwang]

Hi, During my time in 'Nam in the mid-late --60's I used to visit Marine sniper school, there I witnessed instructor one of original sniper during WW2 hitting at a target 500 meters away, he was aiming it at higher angle pretty well into the air. Canuck JTF sniper in Afghanistan confirmed kill at more that 2000yards. All law of simple physics. Read about Dr Bull who was assassinated by Israeli rumor was he tried to build monster canons for Saddam Hussein. Same as long range missiles.

[HeyBub]

Here's a bullets journal, taken from a Jack Reacher novel:

First thing out of the barrel of Reacher's Barrett was a blast of hot gas. The powder in the cartridge exploded in a fraction of a millionth of a second and expanded to a super-heated bubble. That bubble of gas hurled the bullet down the barrel and forced ahead of it and around it to explode out into the atmosphere. Most of it was smashed sideways by the muzzle brake in a perfectly balanced radial pattern, like a doughnut, so that the recoil moved the barrel straight back against Reacher's shoulder without deflecting it either sideways or up or down. Meanwhile, behind it, the bullet was starting to spin inside the barrel as the rifling grooves grabbed at it.

Then the gas ahead of the bullet was heating the oxygen in the air to the point where the air caught fire. There was a brief flash of flame and the bullet burst out through the exact center of it, spearing through the burned air at nineteen hundred miles an hour. A thousandth of a second later, it was six feet away, and its sound was bravely chasing after it, three times slower.

The bullet took five hundredths of a second to cross the [parade ground], by which time the sound of its shot had just passed Reacher's ears and cleared the ridge of the roof. The bullet had a hand-polished copper jacket and it was flying straight and true, but by the time it had passed soundlessly over McGrath's head it had slowed a little. And the air was moving it. It was moving it right to left as the gentle mountain breeze tugged imperceptibly at it. Half a second into its travel, the bullet had covered thirteen hundred feet and it had moved seven inches to the left.

And it had dropped seven inches. Gravity had pulled it in. The more gravity pulled, the more the bullet slowed. The more it slowed, the more gravity deflected it. It speared onward in a perfect graceful curve. A whole second after leaving the barrel, it was nine hundred yards into its journey. Way past McGrath's running figure, but still over the trees, still three hundred yards short of its target. Another sixth of a second later, it was clear of the trees and alongside the office building. Now it was a slow bullet. It had pulled four feet left and five feet down. It passed well clear of Holly and was twenty feet past her before she heard the hiss in the air. The sound of the shot was still to come.

Reacher's bullet hit Borken in the head a full second and a third after he fired it. It entered the front of his forehead and was out of the back of his skull three ten-thousandths of a second later. In and out without really slowing much more at all, because Borken's skull and brains were nothing to a two-ounce lead projectile with a needle point and a polished metal jacket. The bullet was well over the endless forest beyond before the pressure wave built up in Borken's skull and exploded it.

Reacher was watching it through his scope. Heart in his mouth. A full second and a third is a long time to wait. He watched Borken's skull explode like it had been burst from the inside with a sledgehammer. It came apart like a diagram. Reacher saw curved shards of bone bursting outward and red mist blooming.

[Home Guy]

Nestork wrote a post without making coherent use of the subject line.

Nestork's post -> FAIL.

[hrhofmann]

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nearly as much by

If the cannonball is larger, it must be more affected by air resistance so something is wrong with your conclusions. Now, if the ratio of diameter to weight is different, then maybe what is postulated could be true.

[Ralph Mowery]

It all has to do with the mass (weight) of the bullet. The battle ship guns and rifles shoot the bullets at about the same speed. Simple example is to take a ping pong ball and throw it. Then take a pool ball and throw it. You can throw each one about the same speed. Because the pool ball is heavier, it travels the most. You can also take a grain of sand and the pool ball. This may be more of the relationship of the cannon and rifle. The sand grain will not travel as far. It is too light. It is small enough the air resistance is very much less than the pool ball so that takes the air resistance out of the picture.

Hand gun bullets have about 1/3 the speed of the other bullets. This is mainly because of the barrel length. Gunpowder can only burn so fast and the gun can only take so much pressure. Even if the handgun could be made strong enough to handle the pressusre, it would be so heavy that no one would want to carry it around. It would also have so much recoil that it would hirt too much to shoot it.

[Doug Miller]

"hr(bob) [e-mail]" wrote in news:e2255331-85a6-40d8-8f91- [e-mail]:

So you think a cannonball is more affected by air resistance than a BB ???

No, something is wrong with your reasoning. The *total* force of air resistance acting on the larger object is of course greater, but _in proportion to its mass_ it's much smaller.

You are overlooking the fact that the effect of air resistance is proportional to the surface area of the object, whereas its momentum is proportional to its mass and thus (if it is of approximately uniform density) to its volume -- hence the larger the object (assuming constant density) the *lower* the *proportional* effect of air resistance.

And *of course* the ratio of diameter to mass (not weight) is different.

Consider two solid spheres, one 1 cm in diameter, the other 2 cm in diameter. Since volume is proportional to the *cube* of the radius, the volume of the second is 8 times that of the first, and if they are made of the same material, the ratio of their masses is also

8:1, while the ratio of the diameters is 2:1. I'll leave it to you to calculate the ratio of the surface areas.

[Doug Miller]

"HeyBub" wrote in news:3oudnenLALdLv07NnZ2dnUVZ [e-mail]:

[snip]

Ummmm, no. Gravity does *not* cause the bullet's horizontal velocity to decrease.

Ummmm, no. The longer it was in flight, the more gravity deflected it. Vertical motion due to gravity depends only on the length of time that it's been in motion, and is

*not* affected in the least by horizontal velocity. A bullet fired from a gun parallel to the ground, and a bullet *dropped* from the same height, will strike the ground at the same instant.

[harry]

There are theorotical limitations on how far any simple gun can fire. The longest range gun was the V3 cannon (Tausendfuss) with mulitple charges. Range of over 100miles. German, designed to bombard London from France

I was bombed by the RAF using blockbuster bombs and put out of action before it could be used. But you can go and see what's left of it.

[harry]

[harry]

What a load of crap. And air doesn't burn.

[harry]

[e-mail]:

rtical motion due to

is *not* affected in the

round, and a bullet

Exactly so.

[Don Phillipson]

The largest cannon I have ever heard of was Gerald Bull's HARP on the island of Barbados in the 1960s, constructed from two USN battleship gun barrels fitted end to end:

original HARP idea (approx. 1960) was that it would be cheaper to launch satellites (then usually orbiting at 100 to 500 miles altitude) from reuseable guns rather than rockets expended in use: but Bull never got into orbit, (The maximum altitude mentioned here is 66 km.)

Bull was a fascinating individual, the youngest Toronto PhD ever (at 21) in his day, employed as a military researcher by the Canadian Defence Research Board, funded partly by the US Army gun research branch, and eased out because he seemed more interested in space research than weapons. Twenty years later he was active in 105 mm. artillery and ammunition supply, eventually assassinated in mysterious circumstances.

[George]

It certainly is a fanciful "heybub" style story but rather inaccurate.

[Vic Smith]

motion due to

*not* affected in the

and a bullet

Hey, you spoiled the story! Read your example above of how gravity works on a bullet many years ago, and never saw a better one since. Because no more need be said.

[nestork]

OK, I read through all the posts. Thanks guys.

I guess the analogy between throwing a ping pong ball and throwing a golf ball speaks loudest to me. Both would start out with the same initial velocity and both would encounter the same amount of air resistance, but the smaller mass of the ping pong ball would be more affected by that air resistance, and slow down much faster.

BUT, if that's true, then it would also apply to objects smaller than a bullet. I'm thinking that there are different size pellets in shot gun shells. Some shot gun shells have lots of tiny pellets, whereas other have a fewer number of large pellets. In both cases, however, the pellets are made of lead (I think) and so the difference in density between the pellets and the surrounding air would be identical. Does anyone know if the shells with fewer large pellets have a longer range than those with lots of small pellets? If air resistance is the key, then it would stand to reason that they would. Larger, heavier pellets should be less affected by air resistance, and therefore slow down less and travel further.