Michigander
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Every post in this thread makes sense to me. 
Strange physics question... (gun related, but kinda long)
- Thread starter Dionysusigma
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P95Carry
Moderator Emeritus
Jamz .. try one of these ....
or
molonlabe
Member
Heisenberg was stopped for speeding.
The state trooper asks "Do you know how fast you were going?
Heisenberg replies "NO, but I know where I am.
The state trooper asks "Do you know how fast you were going?
Heisenberg replies "NO, but I know where I am.
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Erik Jensen
Member
I tryed this, and it fell right out the other end!
of course, my favorite gun is my 1911, but still.....
Got to thinking about this and it is possible to get no report with a long barrel.
The bullet would have to be accelerated very rapidly at first and then its momentum would have to carry it through the rest of the barrel.
It's possible for the bullet to exit at a decent velocity with zero or even negative pressure behind it if it has sufficient momentum to carry it through the remainder of the barrel after it begins decelerating.
I think this would work best with heavy projectiles and large bore diameter. The bullet weight would keep the momentum high even as the velocity falls off, and the large bore diameter gives more space for the gases to expand into as the bullet moves down the bore.
The bullet would have to be accelerated very rapidly at first and then its momentum would have to carry it through the rest of the barrel.
It's possible for the bullet to exit at a decent velocity with zero or even negative pressure behind it if it has sufficient momentum to carry it through the remainder of the barrel after it begins decelerating.
I think this would work best with heavy projectiles and large bore diameter. The bullet weight would keep the momentum high even as the velocity falls off, and the large bore diameter gives more space for the gases to expand into as the bullet moves down the bore.
ConcernedCitizen
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As far as I know, there was a 9mm ammo designed for SMGs, called Hirtenberger. I heard it was loaded VERY HOT, and had a tendency to blow up guns on occasion. It might have been their 5.56 ammo that had problems, I can't remember exactly, but I heard all of their ammo is HOT.
As for the pigeon question, it says "If 19 pigeons are sitting on a fence, 4 hop down onto the ground, and I shoot 2 of them, how many are left, actually, sitting on the fence?"
That is a trick question, because it did not specify whether the 2 pigeons shot were on the ground or the fence.
Of course, that doesn't take into account the "deaf flock of mentally challenged flying rats" theory...
So, exactly how much is my 2 cents worth?
As for the pigeon question, it says "If 19 pigeons are sitting on a fence, 4 hop down onto the ground, and I shoot 2 of them, how many are left, actually, sitting on the fence?"
That is a trick question, because it did not specify whether the 2 pigeons shot were on the ground or the fence.
Of course, that doesn't take into account the "deaf flock of mentally challenged flying rats" theory...
So, exactly how much is my 2 cents worth?
Harry Tuttle
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de combustion consumes the air in the casing
when the bullet leaves the bore
the remaining fuel oxidizes in the free air
when the bullet leaves the bore
the remaining fuel oxidizes in the free air
FNFiveSeven
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uhhhh Harry
gunpowder doesn't require oxygen from the air to burn. You can burn gunpowder under helium if you want, air has nothing to do with it.
gunpowder doesn't require oxygen from the air to burn. You can burn gunpowder under helium if you want, air has nothing to do with it.
Harry Tuttle
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yes the gunpowder contains an oxidizer, but free air oxygen is a potential source for uncontained burning and sound generation
mfree
Member
Here's a line of thought...
A bullet is accellerated to supersonic speeds in a barrel, i.e. faster than the speed of sound.
The pressure wave from the burning propellent is only capable of travelling at the speed of sound in the material in which it moves, which is the pressurized hot gas field in the barrel.
Wouldn't there be a point with long barrels where the momentum of the bullet would carry it past the pressure wave where it would then be under a negative pressure and *retained* by the pressure in the barrel? In the time frame we're talking about, the environment in the barrel is never really homogenous and the speed of fluid movements comes into effect....
....get this theory down pat, do the math, and you've got a way to devise the perfect barrel length for a given load
A bullet is accellerated to supersonic speeds in a barrel, i.e. faster than the speed of sound.
The pressure wave from the burning propellent is only capable of travelling at the speed of sound in the material in which it moves, which is the pressurized hot gas field in the barrel.
Wouldn't there be a point with long barrels where the momentum of the bullet would carry it past the pressure wave where it would then be under a negative pressure and *retained* by the pressure in the barrel? In the time frame we're talking about, the environment in the barrel is never really homogenous and the speed of fluid movements comes into effect....
....get this theory down pat, do the math, and you've got a way to devise the perfect barrel length for a given load
Brad Johnson
Member
(1) 'Which came first, the chicken or the egg?'
- Who cares as long as they are served with a side of bisquits and gravy.
(2) 'Why did the chicken cross the road?'
- Because it was thrown.
(3) 'Was, 'Fuzzy Wuzzy' really fuzzy?'
- Not if he used the right conditioner.
(4) 'How many angels can fit on the head of a pin?'
- I lost 500 bucks on them in the playoffs, so who cares!
(5) 'If 19 pigeons are sitting on a fence, 4 hop down onto the ground, and I shoot 2 of them, how many are left, actually, sitting on the fence?'
- They were sitting on a fence and milling around on the ground, and you only hit two. Boy, are you a crappy shot.
(6) 'Two rabbits are confined inside the same cage; one of them is, 'in heat'. Given a normal gestation period of 65 days and a typical birth rate of 8 to 10 bunnies per litter, with 2/3's of them female, how many bunnies will there be at the end of the year?'
- None. Just after you posed the question I sold them and bought a llama.
Brad
- Who cares as long as they are served with a side of bisquits and gravy.
(2) 'Why did the chicken cross the road?'
- Because it was thrown.
(3) 'Was, 'Fuzzy Wuzzy' really fuzzy?'
- Not if he used the right conditioner.
(4) 'How many angels can fit on the head of a pin?'
- I lost 500 bucks on them in the playoffs, so who cares!
(5) 'If 19 pigeons are sitting on a fence, 4 hop down onto the ground, and I shoot 2 of them, how many are left, actually, sitting on the fence?'
- They were sitting on a fence and milling around on the ground, and you only hit two. Boy, are you a crappy shot.
(6) 'Two rabbits are confined inside the same cage; one of them is, 'in heat'. Given a normal gestation period of 65 days and a typical birth rate of 8 to 10 bunnies per litter, with 2/3's of them female, how many bunnies will there be at the end of the year?'
- None. Just after you posed the question I sold them and bought a llama.
Brad
carpettbaggerr
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Schrodinger did both. And neither.
If a barrel is long enough, the shots can be very quiet
indeed -- especially if the rounds are subsonic.
http://thehighroad.org/showthread.php?s=&threadid=93004&highlight=Hastings+barrel+extension
molonlabe
Member
Mrs. Schroedinger to Mr. Schroedinger: What the hell did you do to the cat?
It looks half dead!
It looks half dead!
molonlabe
Member
"Wanted, dead or alive : Schroedinger's cat."
molonlabe
Member
Wanted, dead AND alive, Schrödinger's Cat.
molonlabe
Member
Why did the chicken cross the road?
Since the wording of the question implies the absence of an observer
(else the fowl's motivation might easily be deduced), it is evident that
the chicken simultaneously did _and_ did not cross the road. In the face of
this, any speculation as to the bird's purpose must be viewed as mere
sophistry -- and as such is beyond the bounds of this discussion.
Until the actual act or non-act of crossing the road was observed,
the act remained a cloud of probabilities.
Since the wording of the question implies the absence of an observer
(else the fowl's motivation might easily be deduced), it is evident that
the chicken simultaneously did _and_ did not cross the road. In the face of
this, any speculation as to the bird's purpose must be viewed as mere
sophistry -- and as such is beyond the bounds of this discussion.
Until the actual act or non-act of crossing the road was observed,
the act remained a cloud of probabilities.
jefnvk
Member
I do believe there is. I think the original post was refering to WWII. IN wartime, I could absolutely see using the same ammo out of SMG and pistol. But, in peacetime, for police use I wouldn;t see why there isn;t a special round. Ammo interchangability isn't so much of an issue to them.
benEzra
Moderator Emeritus
Some muzzle flash results from the fact that some of the combustion PRODUCTS are flammable, but do not burn in the oxygen-starved environment behind the bullet. (The powder is self-oxidizing, but the combustion products aren't.) When some of those hot combustion products hit the air outside the barrel, they undergo further combustion and produce some visible flash. I think carbon monoxide and POSSIBLY hydrogen may be present in amounts sufficient to produce a flash. (And no, carbon monoxide poisoning isn't a problem because the CO is HOT and oxidizes to CO2 as soon as it encounters atmospheric oxygen.)
Actually, it is, but not the speed of sound in air; rather, the speed of sound in 35,000 psi, 1000-degree nitrocellulose/nitroglycerin decomposition products, which is WAY higher than the speed of sound in sea-level air. It is this factor that limits the ultimate speed of any gunpowder-driven projectile to under 7000 fps; the gas simply can't expand any faster than that, regardless of how light your projectile is.
Brian Dale
Member
{bullhorn} All right, molonlabe, put down the cat and the textbook, and step away from the chalkboard! {/bullhorn}
There was an experiment done and published in a gun magazine to determine how much velocity would be lost in a long barrel.
I can't remember the results, unfortunately, but I seem to remember that it was quite a bit longer than a rifle barrel.
They had to weld together a few lengths of barrel stock to get the results.
I can't remember the results, unfortunately, but I seem to remember that it was quite a bit longer than a rifle barrel.
They had to weld together a few lengths of barrel stock to get the results.
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