Mile-Per-Second Cartridge: Is it possible?

Making such a rifle would no doubt require some kind of advanced recoil system as well.

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Or just make it heavy. Simpler.

alloy

I'm thinking that a barrel made from an alloy of depleted uranium and tungsten carbide, and bullets made with a solid copper core with a nickel jacket?

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Maybe. There is a lot of controversy about using depleted uranium. It is radioactive (mildly.....but still) and Uranium is, like lead, a toxic metal.
I'm sure that I wouldn't be shooting through a barrel made of an alloy of that.
The idea of super hard alloy, though, is a good one.
Pete

What's the difference between a 22-243 and a .22 Cheetah?

I know a hobbyist who claims to have gotten 45-4600 fps out of a .22 cheetah.

I would agree with many of the other posters, a saboted dart made out of something very dense would be one possible way of doing it. Maybe a tungsen dart? Threads like this one are one of the reasons I like the highroad.

i think the limiting factor here is going to be the propellant. if 5300fps is the limit acheivable with current nitro gun powder, then we would need a bullet and or barrel coating that reduces the coefficent of friction to 0. or a propellant that was stable enough to go faster to make up for frictional losses. even if we got barrel/bullet friction to 0, and the bullet left the muzzle at 5300fps, it would start to slow down in the air. it would still take the projectile over a second to travel a mile.

stuff we've got: the technical knowhow to make barrels of any alloy, in any length, in any twist we want. the knowhow to make bullets of any shape of any alloy. the capability to use and apply nano surface treatments to reduce the coeffecient of friction to near 0.

stuff we need: a propellant that burns at above 5300fps, that is stable enough to carry around in your pocket, opperates at a wide temperature range, and opperates at low enough pressure to be contained by a small enough chamber as to be man portable.

so, if we had a .30 calibre rifle with a 30" barrel, a 1 in 20 twist, coated with some sort of super whizz-bang new nano-ceramic coating and a chamber and leade made of tungsten ceramic composite, firing a projectile in the 4 or 5 bc range at a muzzle velocity of arround 5500 or so then yes, we would have a man portable firearm capable of firing a bullet a mile in under a second.

There are several articles out today about a test of the Navy's railgun project. They are a little vague about velocity, but the figure Mach 7 was mentioned. Google tells me that's about 7,815 fps.

I'm no physicist, but I would think that a tiny bit of high explosive such as RDX could be harnessed to push a very small & light projectile in a predetermined direction. A firearm designed to use RDX as a propellant, though, would have to be built like a bank vault in order to contain the tremendously high chamber pressure.

I threw out the depleted uranium just as an example because it's so tough, but I agree that it probably wouldn't be practical. I remember when I began my tool and die apprenticeship back in the late 70's. By then we had some pretty impressive steels in comparison to what was available in 1900, and in the last 30 years new alloys and heat treatment methods have gotten even better. We can't ceate new elements, but we can develop new techniques that might allow us to form new alloys that'll solve the problem of being strong enough to contain the combustion of some new propellant and be tough enough to not erode away from the ultra fast bullet. I bet 100 years from now everyone will be looking back at modern smokeless powder much like we look at black powder and damascus barrels today.

Here's the aforementioned railgun project:

http://cosmiclog.msnbc.msn.com/_news/2010/12/10/5626100-railgun-shot-heard-round-the-world

Makes firearms as we know them kinda seem like gnats on God's windshield.

Isher

I think that 100 years from now, pretty much all weapons will reach a velocity of 186,000 miles per second.

It'd be a tough proposition, for sure. Aside from the self-destruct question...which I've seen happen with a .220 Swift pushing the envelope with 50-grain bullets...simply launching the bullet as 5280 feet won't cover a mile in one second, as Owen noted.

Not only does the bullet start to decelerate the instant it hits the air...the faster it's going when it does, the more rapidly it slows down for a given weight/mass.

As an example and assuming equal ballistic efficiency, two .30 caliber bullets...a 150 and a 165 grainer...If the initial velocity is 2800 and 2600 fps respectively, the lighter bullet will lose a larger percentage of its velocity at a given distance than the 165. By the time they've both covered 450 yards, the heavier, initially slower bullet has caught up with the lighter one. At about 500 yards, it will pass it.

I tried .22 sabots in a 300 Weatherby and got close to 5000 FPS but accuracy was non-existant so I quit.

Something in me head keeps saying "railgun".

However, railguns tend to have issues with the ammo burning up at higher powers, the same powers needed to acheive that kind of velocity.

I suspect the only thing keeping us from having a mile per second is thermal management. Perhaps a soft projectile with a chilled-water cooled copper barrel would do it, but then we'd have range issues due to the ammo breaking up.

This is a good question, it's practically a catch-22.

I have a question for the experts. Not exactly in the spirit of the original OPs quest, but I hope close enough.

What happens when a fast moving fighter plane fires it's cannon???

The 20mm on the current fighters fires it's bullet at a speed over 3,300 fps. Now take into account that even the old F-15 fighters can go about 1,650 mph or 2,420 fps. Adding the two we get 5,720 fps or about 440 fps over our magic number.

While I am not suggesting that we duct tape Bubba to the tail fin, and let him fire his hot handloaded 22-250 as the plane does a speed run (no matter how much fun it would be) would it work (i.e get the speed desired)??

For you former Air Force/Navy guys, do they, or have they ever fired the cannon at high speed???

This is wandering way OT, but did you hear about the jet that shot itself down?

On Sep 21, 1956 Grumman test pilot Tom Attridge shot himself down in a graphic demonstration of two objects occupying the wrong place at the same time—one being a Grumman F11F-1 Tiger [138260], the other a gaggle of its own bullets..

It happened on the second run of test-firing four 20mm cannon at Mach 1.0 speeds. At 20,000' Attridge entered a shallow dive of 20°, accelerating in afterburner, and at 13,000' pulled the trigger for a four-second burst, then another to empty the belts. During the firing run the F11F continued its descent, and upon arriving at 7,000', the armor-glass windshield was struck, but not penetrated, by an object..

Attridge throttled back to slow down and prevent cave-in of the windshield, flying back to Grumman's Long Island field at 230 mph. He radioed that a gash in the outboard side of the right engine's intake lip was the only apparent sign of damage other than for the glass, but that 78 percent was maximum available power without engine roughness occurring..

Two miles from base, at 1,200' with flaps and wheels down, it became evident from the sink rate that the runway could not be gained on 78 percent power. Attridge applied power and said "the engine sounded like it was tearing up." It then lost power completely. He pulled up the gear and settled into trees less than a mile short of the runway, traveling 300 feet and losing a right wing and stabilizer in the process. Fire broke out, but, despite injuries, Attridge managed to exit the plane and get away safely, to be picked up by Grumman's rescue helicopter.

Examination of the F11F established there were three hits—in the windshield, the right engine intake, and the nose cone. The engine's inlet guide vanes were struck, and a battered 20mm projectile was found in the first compressor stage..

How did this happen? The combination of conditions reponsible for the event was (1) the decay in projectile velocity and trajectory drop; (2) the approximate 0.5-G descent of the F11F, due in part to its nose pitching down from firing low-mounted guns; (3) alignment of the boresight line of 0° to the line of flight. With that 0.5-G dive, Attridge had flown below the trajectory of his bullets and, 11 seconds later, flew through them as their flight paths met.

Jubjub had it right. The 120mm cannon on the M1A1 tanks was over 5k. The combination of a smooth bore and a fin stabilized saboted projectile helped.

Suspect the "12 Ga from hell" if loaded with a saboted bullet in a smooth bore, could actually be the speed king here.

Why not use the Rail Gun theory, but.. with expanding gasses? The limiting factor on a centerfire cartridge is that its the primary and sole propulsive element. There's a reason coil guns have more than one electromagnet; an electromagnet can only apply so much force on it's own.

So instead of one cartridge, you have several along the barrel, timed to fire in sequence, injecting the gas immediately after the bullet passes each cartridge. Burn rates of powder aside - what you lose on a standard cartridge is the detonation follows physics, and suffers from inverse square law. As volume doubles, the square root of the force is applied. Eventually there's no more force as force applied by the expanding gas is reduced to zero.

Having additional injections of, say, 50,000 PSI gasses from subsequent combustions would continue to accelerate the projectile up the barrel, right up to the point the projectile disintegrates from friction in the barrel.

The mechanics involved for timing the charges would be a real nightmare, but if you could sustain 40-50,000 PSI consistently for any length of time behind the projectile, it's going to go as fast as the material it's made of allows. With modern computers capable of picosecond or faster timing, it wouldn't be impossible.

It'd effectively make the firing mechanism the "multi-stage rocket" of projectiles.