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High Velocity Super Gun


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#1 thiskid13

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Posted 22 March 2004 - 09:28 PM

if been making little homemade guns for awhile now and so far the best gun i've ever created is a simple ball valve single shot gun that has a 0.5" diameter barrel that can be ajusted to be from 11" to 11' long. the tank is about 2' long and is 1.5" diameter abs piping. i fill it with a compresser normally to 125psi. i usually shoot AA batteries EDIT:0.4" LEAD WEIGHTS, BOLTS AND BITS OF STEEL THAT FIT. with the 11" barrel it has a low velocity of around 250 fps and a max range of about 200'. with the 3' barrel it has a muzzel velocity of about 500fps and a range of about 400 some odd feet. with the 6 foot barrel the velocity is about 700fps and finally with the 9' barrel it has speedy velocity approaching 1000fps. pretty good considering sound waves travel at 1150fps. with the 11' foot barrel there isn't much difference. with the 9' barrel i can shoot horizontally and the projectel will go about 700-800 feet before it hits the ground. i haven't had enough space to test its full range but i'm guessing it can shoot more than 2000 feet. it destroys just about anything you put in front of it and when you shoot over long distances you can hear the projectile traveling through the air, making a slight wooshing sound, its sweet.
EDIT: I DO NOT ONLY SHOOT BATTERIES, IF YOU READ ALL THE POSTS YOU WILL FIND THAT THIS HAS BEEN RESOLVED. I ALSO SHOOT 0.4" LEAD WEIGHTS, BOLTS AND BITS OF STEEL THAT FIT.

Edited by thiskid13, 28 March 2004 - 11:37 AM.

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#2 Black Wrath

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Posted 22 March 2004 - 09:35 PM

You're shooting batteries with a spudgun basically. Um, dangerous, yes, interesting... not really. It's been done so many times before. The ranges you claim are hard to believe for me, because I don't think that you can shoot a AA battery 2000'. I believe 200-400' because it is quite heavy and areodynamic. Yet the velocity you claim seems a little too fast for a pneumatic spudgun. Those are just my thoughts though.

Edited by Xx_Black-Wrath_xX, 22 March 2004 - 09:36 PM.

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#3 CustomSnake202

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Posted 22 March 2004 - 10:25 PM

Those spud guns scare the crap out of me. I don't see why you would want something that powerful that could easily kill someone. But hey, whatever floats your banana boat.
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#4 Oroku Saki

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Posted 22 March 2004 - 11:12 PM

Spud guns are fun, but if I see you use that thing in a Nerf War, my steel toed boot is gonna be buried up your ass. Once a projectile gets over around 350-400+ FPS, it starts to become dangerous to get shot at.

But all that bantering aside. It is still fun to tinker with higher velocity cannons and stuff. The problem is that so many people do this, and very few significant advancements have been made in spud cannon technology. The designs and concepts have been practically the same for years.

Edited by Oroku_Saki, 22 March 2004 - 11:24 PM.

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#5 thiskid13

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Posted 23 March 2004 - 03:36 PM

the shots were chronographed with a paintball chrono so the velocties i mentioned are true. i do understand that this is the most unoriginal potato gun design there is and i am fully aware that it could easly kill someone so i'm carefull with it and never plan on shooting anybody for that reason. the thing that i find makes it different is how high the velocity is. also, it can shoot much much further than 400' feet. shooting it horozontally the projectile hits the ground at about 400-500' so shooting it on an angle it can go extremely far. it doesn't quite reach 1000fps its more like 950 and 980fps. but when something is going that fast it can cover a long distance before it begins to slow down so i'm sure it can easily make 2000' or even more.
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#6 Oroku Saki

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Posted 25 March 2004 - 01:40 AM

Hey, it's fun to blast things with high-velocity stuff, but I really don't understand a practical use for something like this. I can see the significance if you were building say, a homemade Nerf gun, or even a low velocity cannon that shoots paintballs.

Also, I have a question on what type of paintball chronograph you are using. Do PB chronographs even measure this high of velocity accurately?
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#7 thiskid13

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Posted 25 March 2004 - 05:16 PM

the only practicle use of this gun might be hunting, but since i don't hunt i just shoot it for fun if i'm bored. the velocities probably aren't very accurate, turns out the chrono was only meant for 450fps max but that doesn't mean it isn't shooting at those speeds. if it measures dead on up to 450fps then say at 550fps it might instead measure 536fps or 576fps or some other number thats off by a relativley small amount. what i mean to say is that even if it wasn't 100% accurate it probably gave a velocity that was close enough. since velocity is a statistic that isn't 100% accurate we'll just assume its faster than 450fps and leave it at that. the range is right though. i shot it into the field behind my house when there was snow on the ground at about a 10* angle. when it shot it i followed the projectile with my eyes until it went out of sight which was at the very most a second. maybe a bit more than a second after that i saw a puff of snow fly up at about 600 feet away. at point blank it shot through 3 sheets of plywood, each one was 1/2 an inch thick and also at point bank it shot through 5 inches of magazines. i've tryed shooting potatoes out of it but the break apart as soon as they hit the air. i am very confident that it is approaching 1000fps and that at 45" it could shoot around 2000' with the right projectile.
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#8 Ice Nine

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Posted 25 March 2004 - 05:21 PM

Fuck, dude, I highly doubt that your spudgun is approching speeds of Mach 1.
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#9 Grinch

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Posted 25 March 2004 - 06:45 PM

it could shoot around 2000' with the right projectile.

Sure. You do realize how far 2000 feet is, right? That's a little less than six football fields.
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#10 Bobert

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Posted 25 March 2004 - 09:46 PM

Fuck, dude, I highly doubt that your spudgun is approching speeds of Mach 1.

Actually, it is quite possible. I have a C02 powered air gun that fires .177 pelets that can easily get 1100fps. By the way it is a crosman hunter series
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#11 merlinski

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Posted 25 March 2004 - 10:31 PM

Fuck, dude, I highly doubt that your spudgun is approching speeds of Mach 1.

Actually, it is quite possible. I have a C02 powered air gun that fires .177 pelets that can easily get 1100fps. By the way it is a crosman hunter series

Actually, there's no correlation between the two whatsoever. Think about the mass difference between a .177 pellet and a AA battery. Not to mention the drag constant. An AA battery is like a .50 cal round. In order to shoot that near the speed of sound, you'd need foot-pounds approaching those generated in a Browning M81 .50 cal loser rifle.
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#12 thiskid13

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Posted 26 March 2004 - 12:16 AM

think about it, the pressure in the tank is 125 psi, the diameter of the barrel is 0.5" but since its round the theres about 0.4 square inches of area that the air is pressing on. at 125psi that makes the pressure on an area of 0.4 square inches so about 50 pounds pushing forward on the battery. air on its own with nothing in front of it when its under that pressure can easily reach just under the speed of sound. its impossible for it to brake it though because the air flow chokes before it does. it gets to just under the speed of sound and stops accelerating. so it is very possible to get things up to those speeds with just air pressure. now think about how much a little battery is going to resist 50 pounds of pressure. the air at that pressure isn't slowed down much by the battery so it can still get up to those speeds, it just takes longer. thats why with the 9 foot and 11 foot barrels it can shoot at these speeds, it gives the battery enough acceleration time to get to get going that fast. it only works with the super long barrels though so its really impractical to shoot at those velocties. I was shooting it with a friend once, we aimed it at a stone pile about 400 feet away. as soon as i pulled the valve you could hear the burst of air and not even a second later we see a cloud of dust poof up exactly where the gun was pointing at. it was a lazer, the shot didn't drop at all and it was there almost instantly. imagine if i had arced that upwards how far it would go. when you shoot it over long distances the sound of the projectile is louder than the actual shot. it isn't making crack but more of a slicing noise. its loud enough that you can hear the projectile moving through the air even at 300 and 400 feet away.

Edited by thiskid13, 26 March 2004 - 12:18 AM.

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#13 cxwq

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Posted 26 March 2004 - 01:09 AM

think about it, the pressure in the tank is 125 psi, the diameter of the barrel is 0.5" but since its round the theres about 0.4 square inches of area that the air is pressing on. at 125psi that makes the pressure on an area of 0.4 square inches so about 50 pounds pushing forward on the battery.

Your logic is... interesting. The cross-sectional area of a .5" diameter pipe is about .2 square inches. You've also made a number of logical leaps that are intuitively plausible but not backed by any kind of kinematic equations.

I find it easy to believe you could launch an AA battery 2000'. This isn't a nerf gun, guys... If I can launch a bit of foam with a fishing weight in it 200'+ with a toy gun, it stands to reason that an air cannon can launch a metal slug many times that distance.

I find it difficult to believe you're getting anywhere near 1000 fps. The problem here is that you're limited by the speed you can open the ball valve. This is a significant problem when you're working with pressures that high. To get anything remotely near supersonic velocities you'll need a two stage valve that opens fast. I don't care what the PB chrono says, they're not all that accurate and aren't made to measure anything over a few hundred fps. Your attempt to extrapolate error margins from no data is interesting but doesn't hold much weight. Personally, I doubt you're getting more than 4-500 fps.
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#14 Oroku Saki

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Posted 26 March 2004 - 02:11 AM

the only practicle use of this gun might be hunting.

If you are going to use something like that for hunting, you might as well just use a regular gun or bow like the rest of the hunters out there. It's cheaper to fire a bullet than a freakin' battery at an animal, and it is way more effective.

I figured that paintball chronographs were not that accurate anyway, especially for something with that kind of velocity.

An AA battery is like a .50 cal round. In order to shoot that near the speed of sound, you'd need foot-pounds approaching those generated in a Browning M81 .50 cal loser rifle.


The bullet fired from .50 caliber loser rounds are much smaller than a AA battery, so to fire a battery with that kind of magnitude, you are going to need more propelling power than a .50 caliber loser rifle.

Like Cxwq, I also question how you can achieve the muzzle velocity you claim using only 125psi. Correct me if i'm wrong, but isn't that the kind of pressure used in regular paintball guns?
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#15 thiskid13

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Posted 26 March 2004 - 04:35 PM

you must have no idea what i'm talking about. you're right though, 125psi is the pressure used in paintball guns but how does that prove anything? my gun has different dimensions than a paintball gun. the barrel in a paintball gun is about 1 foot give or take when the barrel on my gun is 9 feet. if after a foot of travel through a barrel, a paintball can reach 300fps than how is it so impossible for a projectile to get up around 1000 fps after 9 feet of travel. you must not realize that the longer a barrel is the longer the projectile has to go before it leaves the barrel. if a projectile is in the barrel with froce being exherted on it for longer it will be accelerating for longer. if its accelerating for longer then it gets up to i higher velocity.i aslo never said that i go hunting with it, i just listed that as something practical you could do with. just cause i said it shoots batteries doesn't mean that thats only what i shoot, i shoot screws, fishing sinkers and other pieces of metal that fit. i just said AA batteries so that you'd know the size of projectile that i'm shooting.

Edited by thiskid13, 26 March 2004 - 04:42 PM.

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#16 merlinski

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Posted 26 March 2004 - 05:14 PM

you must have no idea what i'm talking about. you're right though, 125psi is the pressure used in paintball guns but how does that prove anything? my gun has different dimensions than a paintball gun. the barrel in a paintball gun is about 1 foot give or take when the barrel on my gun is 9 feet. if after a foot of travel through a barrel, a paintball can reach 300fps than how is it so impossible for a projectile to get up around 1000 fps after 9 feet of travel. you must not realize that the longer a barrel is the longer the projectile has to go before it leaves the barrel. if a projectile is in the barrel with froce being exherted on it for longer it will be accelerating for longer. if its accelerating for longer then it gets up to i higher velocity.i aslo never said that i go hunting with it, i just listed that as something practical you could do with. just cause i said it shoots batteries doesn't mean that thats only what i shoot, i shoot screws, fishing sinkers and other pieces of metal that fit. i just said AA batteries so that you'd know the size of projectile that i'm shooting.

Actually all of us here have a pretty good idea of what you're talking about.

About the length of a barrel:

I realize that the longer the barrel, the longer the pressure exerts force. However, you're ignoring one crucial factor. As the barrel gets longer and the battery travels longer down the barrel, the volume of the airspace increases. For example, with 9 feet of barrel .5'' thick, you get 21.6 cubic inches of volume in the barrel alone. Now compare that to your original air tank, which at 2' long and 1.5'' thick has a volume of 42 cubic inches. If you have 125 psi initially, your pressure once the battery reaches the end of the barrel will be only about 80 psi. Considering that atmospheric pressure is 14.7 psi and your surface area is .2 square inches, you have about 13 pounds of force at the end of the barrel, as compared to 22 pounds initially. That's quite a decrease, and that doesn't even take into account the most important factor. When you get a barrel that long, friction has a huge effect on the projectile. The battery isn't going to float through the barrel without touching the sides. In fact, the longer your barrel is, the longer the battery scrapes the sides and the greater your kinetic energy loss is.

All of this doesn't even address the fact that your paintball comparison is flawed. A paintball that reaches 300 fps in a 1 foot barrel isn't nearly as heavy as a AA battery. The basic law F=MA means that if you increase the mass, the acceleration decreases at a rate inversely proportional to your mass change.
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#17 Oroku Saki

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Posted 26 March 2004 - 05:52 PM

I'm not really an expert on physics, but looking at merlinski's calculations, there is no way in hell that 13 lbs of force at the end of the barrel from firing at 125psi is going to achieve 1000 fps since the battery has a higher mass than a regular bullet or paintball to begin with.

With this increased mass load, the range and velocity is going to be terrible. If you increase the amount of pressure, you might be able to increase the muzzle velocity and range, but PVC is only designed to handle up to 600 psi, which I still don't think is enough pressure to achieve the range and velocity that you claim by firing batteries.
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#18 Bobert

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Posted 26 March 2004 - 06:33 PM

Fuck, dude, I highly doubt that your spudgun is approching speeds of Mach 1.

Actually, it is quite possible. I have a C02 powered air gun that fires .177 pelets that can easily get 1100fps. By the way it is a crosman hunter series

Actually, there's no correlation between the two whatsoever. Think about the mass difference between a .177 pellet and a AA battery. Not to mention the drag constant. An AA battery is like a .50 cal round. In order to shoot that near the speed of sound, you'd need foot-pounds approaching those generated in a Browning M81 .50 cal loser rifle.

oh sorry, i thought he was firing smaller projectiles. but an AA battery is more like a .44 long rifle because ive seen a .50 caliber and its way bigger.
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#19 Oroku Saki

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Posted 26 March 2004 - 06:39 PM

The entire shell is bigger (for either the .50 cal or .44 long), but as far as what I have seen, the bullet itself being fired from the barrel is smaller than a AA battery. As he said before, he fired other objects from his gun, but he claims to achieve an INSANE muzzle velocity and range when firing a AA battery using only 125 psi, which I still think is impossible looking at the specs and data he gave us.

Edited by Oroku_Saki, 26 March 2004 - 06:42 PM.

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#20 thiskid13

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Posted 26 March 2004 - 08:24 PM

ok, so that are no more missconceptions i'll explain re-explain how it works. I shoot AA batteries occasionally, not over long distances though because they're fairly unstable in the air and its harder to control where they go. AA batteries are not what i've recorded the velocities with but i figured they wouldn't shoot much slower than anything else. after reading your calculations, i've realized that AA batteries probably shoot much slower than what i normally use for high velcoities. I usally shoot o.4" lead balls and bolts for velocity measurments. I didn't think of the difference between them. anyways my guess compared to the other projectiles a battery would go about 500-600 fps which is much more realistic. the high velocity shots were with heavy metal objects that were just a little to small for the barrel. I would put a ball of ceran rap behind the shot so that once the pressure got low in the barrel and the ceran rap slowed down, the projectile could keep going with nothing slowing it down. that way the projectile got the very most out of the blast of air with as little friction as possible. come to think of it the lead balls i was shooting were a lot smaller than a battery. a 0.4" lead ball is what i shot through the three 1/2" thick partical boards. its also what i used when i shot at the gravel pile about about 400 feet away and it had almost no time delay between the shot and the puff of dust flying up. i honestly have no problem with using a ball valve and don't have any reason to use anything else. if you put oil on it and work it in a bit, it becomes very easy to open close. when i open it, it isn't gradual, it snaps open and the air bursts out rather than a rush of air that gradualy gets faster. a ball valve has never restricted the air flow of my gun. i also never said it shoots 1000fps i said it APPOACHES 1000fps. this is anywhere from 700-950fps depending on the barrel and projectile. and lastly i understand you all know exactly what you're talking about, i was just refering to one person when i said that and should have used a quote.
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#21 THIRST

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Posted 26 March 2004 - 08:34 PM

Sounds jut like Xcalibur...(no offence X, but both of you didt tell the whole story, and both altered the data).

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#22 thiskid13

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Posted 26 March 2004 - 10:18 PM

i know, i feel a little silly, but it wasn't that I altered my story, everything is still the same except for the type of projectile i shot which isn't drastically smaller.
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#23 Oroku Saki

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Posted 26 March 2004 - 11:51 PM

Whenever you post about something you built or modified, please make sure that you give us proper details. Sometimes leaving out information like that makes the whole thing confusing.
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#24 boltsniper

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Posted 28 March 2004 - 02:05 AM

This is quite interesting. First, I`m not gonna jump out and claim muzzle velocities of near 1000 fps as ridiculous. Although I do beleive it would be very difficult to reach. Lets do a little comparison with numbers. I`ll give the specs for my AR15 for some comparison. An AR15 will shoot 5.56 NATO at with these specs:

Caliber: 223
mass: 55 Grain (0.000246 slug)
Chamber Pressure: 52000 psi ! (2 and a half orders of 10 higher)
Muzzle Velocitty: 3100 fps
Muzzle Energy: 1320 ft-lbs
Barrel Length: 1.33 ft

The known specs for your air rifle shooting a AA battery as you have told us are:

Caliber: 50
mass: 355 grain (0.00157 slugs) (ironically the same mass as a .50 AE round)
Chamber Pressure: 125 psi
Barrel Length: 10 ft (nominal between 9 and 11)

Area = (.5/2)^2*pi = 0.1963 in^2
Force on bullet = P*A = (125) * (0.1963) = 24.5 lbs
Acceleration of projectile = F/m = (24.5) / (0.00157) = 15605.1 ft/s^2
Muzzle Velocity = sqrt(2 * a * d) = sqrt(2 * (15605) * (10)) = 558.7 ft/s

Thats neglecting:
pressure loss around the unsealed projectile
pressure drop due to expansion
friction

So 558 is a high estimate. probably 450-500 fps would be a more realistic value.

Lets see what the pressure would need to be to get a AA battery to 1000 fps.
Known values are:

Caliber: 50
mass: 355 grain (0.00157 slugs)
Muzzle Velocity: 1000 fps
Barrel Length: 10 ft (nominal between 9 and 11)

a = V^2/(2d) = (1000^2)/(2*10) = 50000 f/s^2
F = ma = (0.00157) * (50000) = 78.5 lbs
P = F/A = (78.5) / (0.1963) = 400 psi

Again neglecting pressure loss and friction. A more realistic value would probably be around 500 psi for chamber pressure.

And finally the mass a bullet would have to be to get it to 1000 fps at 125 psi.


Caliber: 50
Muzzle Velocity: 1000 fps
Chamber Pressure: 125 psi
Barrel Length: 10 ft (nominal between 9 and 11)

F = P*A = (125) * (0.1963) = 24.5 lbs
a = V^2/(2d) = (1000^2)/(2*10) = 50000 f/s^2
m = F/a = (24.5) / (50000) = 0.00049 slugs

In laymens terms 0.0071 kg or 109 grains. Account for losses and this would more realistically be around 50-60 grains. About like shooting a 22LR but only in 50 caliber. A dime is probably a pretty good representtaion. But there is not way to shoot a dime without it falling over in the bore. And on top of that the drag would be phenominal and accuracy shit.

So his numbers aren`t so off, although reaching close to 1000 fps sounds a little optomistic unless you are running some incredibly high pressures. As thiskid has said the 10 foot barrel is the key. Although it does create excess friction the increased acceleration time is what gives the better muzzle velocities. There is an optimum barrel length for all bored projectile weapons. There is a barrel length where the force for acceleration is fully countered by firction and the pressure drop. This can be analigous to overexpanded nozzles which is a inherently bad situation in nozzle desgin. Anyway, maybe all this shit will help calm this thread down.


For anyone wondering this post only took me about 10 minutes to do. If it had taken longer I would have said fuck it.

Edited by boltsniper, 28 March 2004 - 02:12 AM.

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#25 MysticFalcon182

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Posted 28 March 2004 - 02:14 AM

Fuck, dude, I highly doubt that your spudgun is approching speeds of Mach 1.

Actually, it is quite possible. I have a C02 powered air gun that fires .177 pelets that can easily get 1100fps. By the way it is a crosman hunter series

Actually, there's no correlation between the two whatsoever. Think about the mass difference between a .177 pellet and a AA battery. Not to mention the drag constant. An AA battery is like a .50 cal round. In order to shoot that near the speed of sound, you'd need foot-pounds approaching those generated in a Browning M81 .50 cal loser rifle.

oh sorry, i thought he was firing smaller projectiles. but an AA battery is more like a .44 long rifle because ive seen a .50 caliber and its way bigger.

I highly doubt this. All I'm going to say.

And do us a favor and make paragraphs.

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