Extreme rifle velocities


PDA






tank mechanic
December 5, 2006, 03:38 AM
If one had sufficient time, money and the necessary equipment, would they be able to make a practical rifle round that reach velocities of 8, 9 or 10 thousand feet per second? Is there a ceiling to how fast a hunter would want a round to travel?

If you enjoyed reading about "Extreme rifle velocities" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
Koobuh
December 5, 2006, 08:05 AM
Those kinds of velocities and 'practical' are a bit of a contrast, don't you think? You're talking about pushing a bullet three to four times faster than modern, conventional rifle rounds are comfortably loaded for.

At those velocities you have to deal with the fact that air friction will literally melt the bullet, and worry about the bullet bursting into little shards inside the barrel; both of these problems have limited the development of magnetically and electrically propelled projectile weapons.

The M1A1 Abrahms tank's main gun fires a DU sabot round at about 5,000 FPS, pretty close to "the velocity limit for chemical propellants", per Wikipedia.

Is it possible? Sure, anything's possible. Not with a stock rifle or with components you can buy off MidwayUSA. Probably not possible with chemical propulsion (barring rockets :D ). But sure, you could theoretically make a gun that pushes a bullet that fast, if you're willing to stretch the definitions of 'rifle' far enough.


No, you don't want a bullet travelling that fast to hit anything you might want to take home. Even a very small projectile at that velocity would make a terrible mess out of anything it hit. Think 'fine red mist' or 'bloody, ragged pelt hanging from the trees' rather than 'small entry, big exit'.
Feasibly, anything over the current magnum velocities of 3,000+ FPS is pretty much overkill (I would argue that even current magnum loads are overkill, YMMV). There's a limit to how much energy you want to be pumping into a game animal via bullet, and typically you upgrade the weight/diameter class of the bullet rather than its velocity if you're hunting bigger, more dangerous game.

shermacman
December 5, 2006, 08:13 AM
I think that creating a .177 caliber bullet made of depleted uranium mounted on .50BMG brass with an extremely fast burning propellant in a very high pressure barrel would be perfect for the squirrels that ate through the trim boards at the roof of my house.

I'm thinking 8,000 fps. Never mind "fine red mist" I'm thinking "fine red vapor".

:D

Geno
December 5, 2006, 08:13 AM
Electronic Propulsion would be required for the 10,000 FPS levels. You won't get off-the-shelf components to propel a projectile at those velocities. The 6,000 FPS isn't so much of a problem, but 10,000? Electronic. This type "rifle" already exists, but it sure isn't for hunting. :D

Doc2005

jmorris
December 5, 2006, 10:39 AM
http://www.maadigriffin.com/sabots.htm has sabots for both .30 cal and the 50 bmg. If I remember correctly you can get 5200fps out of a 180gr .30 cal bullet in 50 bmg. The Remington accelerator (55g .22 in a sabot) velocity is almost 4100 fps. both should be ok for squirrels out to 25 yds or so. The following link is a good read and claims 6000fps+- is the limit with conventional propellant; however, if you pony up for a electromagnetic rail gun you can get 30,000fps

http://homepages.solis.co.uk/~autogun/highvel.htm

Jim Watson
December 5, 2006, 11:24 AM
As I recall, the limit is the expansion of gas nearing its speed of sound for the composition, temperature, and pressure. That is around 4500 fps for powder gases. The few rounds that exceed that are operating in a range of non-steady state and non-ideal gas behavior that the equations do not predict well.
If the expansion exceeds the actual speed of sound in the mix, it forms a shock wave. We call that an explosion, which you do not want in your gun barrel.

EM rail and coil guns are pretty experimental devices themselves.
Study of extra high velocity projectiles without a lot of fuss on the launch equipment is usually done with light gas guns. In which a charge of gunpowder drives a piston that compresses a cylinder of helium to very high pressure. A rupture disk pops, letting it in behind the projectile, usually saboted to reduce sectional density and increase acceleration. The helium because of its low molecular weight and relatively low temperature can expand much more rapidly than hot heavy powder gas and velocities run well over 10,000 fps. Hydrogen would be better except that it is flammable.

Navy_Guns
December 5, 2006, 12:22 PM
http://www.wstf.nasa.gov/Hazard/Hyper/Facility.htm

White Sands test faclility is getting 23,000 fps for testing the impact of orbital debris for NASA.

If you went far enough, you might not even get a red vapor from that pesky squirrel. Imagine hitting it so hard with an ultra dense pellet that you actually create a miniature black hole and you collapse the squirrel into a singularity. I'd pay to see that.

BigG
December 5, 2006, 01:16 PM
I just tested my crude math skills. I remember they used to talk about rockets going 25,000 mph (IIRC). Anyway, I came up with ~ 36,667 feet per second for a rocket traveling 25,000 mph. Is that correct?

What do they use to hold that thing together and keep it from melting? :eek:

Jim Watson
December 5, 2006, 01:32 PM
Most liquid fuel rocket engines circulate fuel or oxidizer around the nozzle as coolant to keep it from melting. Also preheats the fuel for a better burn.

Interesting to read that the Navy light gas guns DO use hydrogen for its low molecular weight and low viscosity. Better keep the fire department on call.

I guess it is like the oxygen compressor at a plant I worked on once. The Air Products engineer said if the compressor caught fire, the enclosure would hold for 45 seconds. Which would be enough because the compressor would burn down and exhaust the oxygen in its cylinders in 30 seconds.

Geno
December 5, 2006, 07:03 PM
I thought they were using electric propulsion. I learn something new everyday. Thanks all.

Doc2005

pvtschultz
December 5, 2006, 07:20 PM
Most rockets can travel that fast because they are in the upper atmosphere or even bordering outer space where the air is extremely thin and there is little drag force. Also, the expansion of gasses is in deed restricted to the speed of sound which is dependent on temperature amoung other things. So at high temperatures and low pressures (densities) the speed of sound is much faster than at standerd pressure and temperature.

AmbulanceDriver
December 5, 2006, 09:07 PM
pvtschultz, you're right regarding rocket speed/drag and low atmospheric pressure. However, I fail to see where gas expansion/speed of sound comes into things?

boilingleadbath
December 6, 2006, 01:01 AM
I know a guy who does, basicaly, weapons research.
A few months ago, he told me that they've built themselves a rather large gun... I think it had a 20mm bore, was 20' long, and fired an aproximatly 300 grain projectile at (an estimated) 9000 fps at the muzzle using something like a pound of powder.

1) It's 20' long, and really heavy (as it should be; it is operating at well over 100,000 psi)
2) The 300 grain projectile had slowed to 7000-some fps by the time it passed the chronograph.

No, the gun was not the end product - simply a research tool.

Steve C
December 6, 2006, 11:37 AM
A rocket takes its fuel with it. As long as the fuel is burning and the gas is escaping the velocity of the rocket will increase. A bullet on the other hand is accelerated only till it exits the barrel and accelerates in the barrel only while the volume of gas increases more than the volume left in the barrel behind the bullet. This is why a .22 lr with a barrel much longer than 20" will begin to deliver less velocity.

ID_shooting
December 6, 2006, 12:11 PM
Gas expansion limited to the speed of sound? Huh :confused:

The speed of sound at sea level and with a temp of 70 degrees is roughly 770 MPH.

A bullet exiting at 3000 FPS is going 2045 MPH.

Conversion info found here:

http://www.reloadbench.com/gloss/conv.html

If the gas from the powder is not expanding at 2045 MPH and the pressure wave is not pushing on the back of the bullet at that velocity, what is causing the bullet to move at that speed?

Please do not tell me to go take a basic physics class, like some like to do, if I am wrong, show me.

Jim Watson
December 6, 2006, 12:17 PM
Gas expansion is generally limited to the speed of sound in the specific medium. Powder gas is not at atmospheric composition, temperature or pressure so Mach is not the same as for air. The figure I have seen is 4500 fps, but that is probably subject to a lot of variation over the millisecond or so the bullet is moving and conditions are changing drastically.
And you can beat that some by using a great lot of powder and using the non-steady state and non-ideal conditions to advantage.

jerkface11
December 6, 2006, 12:32 PM
As i recall from an american rifleman article. The hypervelocity gun at white sands uses IMR 4831 and a lot of it.

Jim Watson
December 6, 2006, 01:38 PM
Yes, but as best I can Google, it is a light gas gun; the powder charge driving a hydrogen compression piston, and is not directly behind the shot.

Clark
December 6, 2006, 08:46 PM
As Jim points out, the speed of sound in a gas is proportional to the root of the pressure and the temperature.

One can only get pressure so high when contained by brass.
One can only get so high a temperture from nitro cellulose.

I think they get higher velocities from shaped charges.
I think they get highter velocities from electric rail guns.

I know some guys that bought some surplus capacitors from a rail gun research for the Reagan Star Wars build up.

My father was given a demonstration of a rail gun that ran on a spinning Copper disc for energy storage. I think they got 10,000 fps.

I have got 4,127 fps with Blue Dot in my .223.
I think I get more with H110, but my Chrony can't get a reading on it.

doopt22
December 9, 2006, 01:49 AM
I thought you guys were reloaders. Normal rifle powders expand at about 5300 ft per sec. with normal powders the fastest you could push a bullet is about 5250 fps. so no matter how big the case is the size of a truck or a peanut shell. max speed is 5250 with the powders you can buy off the shelf. you would have to find a explosive that would expand faster. like c4.

If you enjoyed reading about "Extreme rifle velocities" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!