Theoretical (realistic) upper limit for projectile weapons speed?

I was watching a show on Discovery tonight talking about kinetic weapons and some friends and I were discussing such weapons. My question is, whats the practical theoretical upper limit of such weapons? How close are we too them now. What I’m getting at is how fast would/could we accelerate a projectile weapon in a practical combat weapon system? Are we nearing this theoretical practical limit…or just scratching the system?


Here is how far one system has been developed

Here is a video of one test.

Well, I’ve done a fair ammount of testing of projectile testing. Using an old naval barrel with an 18" ID, and a 10,000lb reaction mass, and an explosive charge, we were able to propel the projectile to just under Mach 4, which is roughly 3,500 feet per second, or just over 2,000 mph. My calculations (which were based on the expected density of air at that altitude and temperature, gravity at that lattitude, ect.) showed that the projectile would go almost straight up, nearly a mile high.

The test was breechless, that is, both ends of the barrel were open. In order keep the 40’ barrel mounted to its supports, nearly equal ammounts of mass must come out both ends. The reaction mass shoots into the ground HARD. There are other tests where the reaction mass goes up, and the penetrator goes into a target (concrete, steel, wood, ect.) on the ground.

Since there are 2 ends to the barrel, I can’t immagine it being used in any practical combat situation just yet.

I misunderstood the OP, when I think of a “projectile”, I subconciously exclude missles, and other rocket powered devices. Most of the testing I did was of the actual warheads, and we propelled them differently than they would have been in a combat situation. The site Dag Otto posted says they can go up to 5,000 fps, though. around Mach 4.5. That’s pretty damn fast!

Railguns send things the fastest. One gun shot a 2 kg projectile at 3 km/second … that’s 10,800 km/hr (6,700 mph), or about Mach 10 …


Someone once told me that the limiting factor for muzzle velocity is the speed of sound in the gas that is being used to propel the projectile. Hydrogen is supposed to be the best gas.

Couldn’t a projectile weapon be made the same way a particle accelerator is. Accelerate the eletrons (or whatever) in a circular ring using magnets to keep them circling, then the trigger releases them by turning off the magnetic field. If you count electrons as projectiles, it would seem the upper limit on speed is the speed of light or damn close to it. Now I don’t think current technology would give you too big a “bang” here, but I see no reason in principle why you couldn’t scale things up.

Agreed: We need a definition of a “projectile”, here. Beyond electrons, even, are photons projectiles? Because we do have laser weapons (mostly designed to blind, but still weapons).

The OP did ask for the highest velocity in a “practical combat weapons system.” The Paris Gun of WWi could throw a projectile 80 miles. In a vacuum this requires a muzzle velocity of 3750 ft/xec. In the atmosphere it would take quite a bit more than that. And I question whether the Paris Gun was really a practical combat weapons system.

When the velocity is increased the possible range is increased and that brings up the problem of targeting. We are talking about weapons systems here and that includes a means of aiming the weapon and correcting for original mis-aiming. In order for conventional artillery to be really effective you need a forward observer to correct the aim. Smart bombs are so effective because their aim is continually corrected in flight by homing on a reflected laser illuminator or on a point of visual contrast on the target.

Extremely high velocity, it seems to me, would be most valuable as a means of penetrating and destroying armored vehicles or underground bunkers.

How much Kinetic energy would be transferred on an 80kg object traveling at 5,000 feet per second? How does that compare to a missle with an explosive charge?

(I think 80kg at 5k f/s is more energy than an object 2kg traveling at 6,200 f/s, is that correct?)

But high velocity projectiles means that a lower mass projectile can hit with the same kinetic energy as a high mass low velocity projectile.

That means your ammo can be lighter, which means the grunts can carry around more rounds without needing a wheelbarrow.

During the underground Pascal-B test of the Operating Plumbob nuclear weapon test series, a cap on the top of the tube used to contain the explosion was accelerated to a speed estimated to be six times the surface escape velocity of the Earth. (The cap undoubtedly distintegrated due to aerodynamic forces and ram heating, and so didn’t go into space.) These miserly velocities you get from mere chemical explosions are limited by the detonation velocity of the resultant products; high energy modern explosives are around 8000 fps, but you can get about three times that with some novel “wet” propellants. Nonetheless, a magnetic accelerator, or something using high energy plasmas should easily exceed the maximum speed of any chemical reaction. Then, the only problem is making a “gun” that can impart and withstand the enormous forces and pressures required without coming apart like a firecracker. Oh, and a projectile that won’t disintegrate into plasma before it hits the target.


That’s my thought about light projectiles. The aerodynamic forces are much larger in relation to the inertia of the projectile which, I would think, would make the aerodynamic properties of the projectile super critical.

It’s not of much use to have a round leave the muzzle at a high velocity if it starts to tumble or wobble shortly thereafter.