Give it up. A conical projectile would be too skimpy for the diameter it would have to be (much less mass than a corresponding rod or needle of the same diameter). There is no advantage to imparting spin, when the angular momentum would be vanishingly small, and "spiral dents" would only impair the physical integrity of the projectile (ice). Flechette rounds have been shot from guns for decades, and an ice flechette would be straightforward.
Good try, but insufficient to preclude a working design. You make too many assumptions. But let's check. You don't actually estimate a volume for the ice "needle" but let us suppose a frontal area of 4 square millimeters and a length of 20 millimeters = 80 cubic millimeters = 0.08 cubic centimeter => 0.08 gram (water ice density ~ 1 gram/cc). Muzzle velocity is not limited so much by energy as by the expansion process, so a muzzle velocity of 150 m/sec is not unreasonable. This is where the sabot comes in, which would provide some mass to moderate the acceleration and structural support for the needle. (There is no shock wave inside an air pistol.) It would aerodynamically peel away once free of the muzzle.
A muzzle velocity of 150 m/sec would equate to 500 fps, or 340 mph, so stick your hand outside the window of your car at that speed and encounter a particle of hail and see if it penetrates. Something pointed would penetrate just fine. Arrows travel at 100 to 300 fps and penetrate most regularly. (I once pounded my fist against an interior wall and discovered I had been penetrated by a nail head. Never noticed it, and I can bet you my fist was not traveling anything close to 340 mph.)
The scope is not B.S. Ever shot a target at 50 feet? Even a 2x scope would come in handy for fine work. Having a reticle zeroed to the weapon would be a lot better than a standard pair of sights. (Why you would scorn something that would improve your aim suggests to me you are not cut out to be an assassin. But that's not a bad thing.)
So, the minimum perforation velocity does not seem to be a problem, and there is no minimum mass limitation if a sabot is used (as it surely would have to be in order to maintain support for the needle and avoid wear/tear against the gun barrel). It looks credible upon analysis.
You missed the part about the ice needle containing the tetrodotoxin. A tiny, tiny dose leads to sure death from an "apparent heart attack." It is not the projectile; it is the poison. You need to read carefully about how this works.
No, muzzle velocity is limited by what can be achieved by the expansion of a gas under pressure and is related to the speed of sound of the gas. This is not a weapon powered by combustion, which makes higher velocities possible (higher gas temperatures). Lewis and Clark had a smoothbore long arm that was powered by compressed air, with which they hunted for (e.g.) deer during their expedition to the Pacific coast. I saw an example of such a gun at the reconstructed Fort Clatsop. No problem getting enough energy to do the job.
The sabot separates from the projectile within a yard of the muzzle. The assassin picks it up and exits Stage Left. This is not theory. Sabots have been around for a long time. They could even be made of environmentally degradable material.
No shock waves. I worked interior ballistics of rocket motors; I know what a shock wave is, and they do not occur for air pistols/rifles. You open a valve, pressure mounts, expands down the barrel, and it is over with. No detonation. No shock. Rapid acceleration onset, but not a shock. Even a conventional gun has a combustion process, not a detonation process. Any such harmonic response by the barrel would be less than for a regular firearm, since things are not happening as fast.
"Second-order factors" at subsonic speed? I am an aerodynamicist by training, and you are talking through your hat. Air density is the only issue, and so long as it doesn't change dramatically over the path of the projectile, there is no problem. And even if it did change, there would not be much effect. Now you are grabbing at straws, since air density would affect ANY projectile weapon. A crosswind would be more of a problem.
As for the scope, I have to chuckle. Somehow a man with a pistol will be ignored---but a man with a pistol AND A SCOPE will stand out like a sore thumb? Do you realize how ridiculous this is? If he is going to be ignored for a pistol, the scope will not make him more obvious. This is part of the stealth of an assassination.
Give it up. A conical projectile would be too skimpy for the diameter it would have to be (much less mass than a corresponding rod or needle of the same diameter). There is no advantage to imparting spin, when the angular momentum would be vanishingly small, and "spiral dents" would only impair the physical integrity of the projectile (ice). Flechette rounds have been shot from guns for decades, and an ice flechette would be straightforward.
Good try, but insufficient to preclude a working design. You make too many assumptions. But let's check. You don't actually estimate a volume for the ice "needle" but let us suppose a frontal area of 4 square millimeters and a length of 20 millimeters = 80 cubic millimeters = 0.08 cubic centimeter => 0.08 gram (water ice density ~ 1 gram/cc). Muzzle velocity is not limited so much by energy as by the expansion process, so a muzzle velocity of 150 m/sec is not unreasonable. This is where the sabot comes in, which would provide some mass to moderate the acceleration and structural support for the needle. (There is no shock wave inside an air pistol.) It would aerodynamically peel away once free of the muzzle.
A muzzle velocity of 150 m/sec would equate to 500 fps, or 340 mph, so stick your hand outside the window of your car at that speed and encounter a particle of hail and see if it penetrates. Something pointed would penetrate just fine. Arrows travel at 100 to 300 fps and penetrate most regularly. (I once pounded my fist against an interior wall and discovered I had been penetrated by a nail head. Never noticed it, and I can bet you my fist was not traveling anything close to 340 mph.)
The scope is not B.S. Ever shot a target at 50 feet? Even a 2x scope would come in handy for fine work. Having a reticle zeroed to the weapon would be a lot better than a standard pair of sights. (Why you would scorn something that would improve your aim suggests to me you are not cut out to be an assassin. But that's not a bad thing.)
So, the minimum perforation velocity does not seem to be a problem, and there is no minimum mass limitation if a sabot is used (as it surely would have to be in order to maintain support for the needle and avoid wear/tear against the gun barrel). It looks credible upon analysis.
You missed the part about the ice needle containing the tetrodotoxin. A tiny, tiny dose leads to sure death from an "apparent heart attack." It is not the projectile; it is the poison. You need to read carefully about how this works.
No, muzzle velocity is limited by what can be achieved by the expansion of a gas under pressure and is related to the speed of sound of the gas. This is not a weapon powered by combustion, which makes higher velocities possible (higher gas temperatures). Lewis and Clark had a smoothbore long arm that was powered by compressed air, with which they hunted for (e.g.) deer during their expedition to the Pacific coast. I saw an example of such a gun at the reconstructed Fort Clatsop. No problem getting enough energy to do the job.
The sabot separates from the projectile within a yard of the muzzle. The assassin picks it up and exits Stage Left. This is not theory. Sabots have been around for a long time. They could even be made of environmentally degradable material.
No shock waves. I worked interior ballistics of rocket motors; I know what a shock wave is, and they do not occur for air pistols/rifles. You open a valve, pressure mounts, expands down the barrel, and it is over with. No detonation. No shock. Rapid acceleration onset, but not a shock. Even a conventional gun has a combustion process, not a detonation process. Any such harmonic response by the barrel would be less than for a regular firearm, since things are not happening as fast.
"Second-order factors" at subsonic speed? I am an aerodynamicist by training, and you are talking through your hat. Air density is the only issue, and so long as it doesn't change dramatically over the path of the projectile, there is no problem. And even if it did change, there would not be much effect. Now you are grabbing at straws, since air density would affect ANY projectile weapon. A crosswind would be more of a problem.
As for the scope, I have to chuckle. Somehow a man with a pistol will be ignored---but a man with a pistol AND A SCOPE will stand out like a sore thumb? Do you realize how ridiculous this is? If he is going to be ignored for a pistol, the scope will not make him more obvious. This is part of the stealth of an assassination.