5 ms·

Both, combined with quite a bit of luck. >Like... Could you just fire the gun, then put the target where the bullet went an fire again and say its mission acco

Both, combined with quite a bit of luck. >Like... Could you just fire the gun, then put the target where the bullet went an fire again and say its mission accomplished because the real goal is just setting up a gun that stable and precise and deterministic? No... slight variations in wind and atmospherics across that distance change too rapidly and significantly to make that viable. (Also, you wouldn't need to, you'd just adjust the windage/elevation on the optics and/or fancy rifle mount.) Also the when the bullet drops from supersonic to subsonic speed, there is a non-deterministic kick that it receives which dramatically reduces accuracy beyond that distance.

spywaregorilla 4y ago
ok wind aside, if that's true, how is it possible to aim it then? It can't possibly be true that you can precisely adjust your aim to hit a specific target if you can't even hit the same target by not changing your aim?
- msherry 4y ago
  That's why this is such an impressive achievement!
  - hamburglar 4y ago
    It’s also why they succeeded on the 69th try instead of the 2nd.
    - thaumasiotes 4y ago
      But that means the approach described above works perfectly. Fire the gun. Place a bullseye over the bullet hole. Then keep firing the gun until you hit the bullseye "again".
      - deleted 4y ago
        [deleted]
      - hamburglar 4y ago
        Well, if you consider that "perfectly," yes, but it could take all day. The ancestor post seemed to be suggesting that if it was so "stable, precise and deterministic" that you could do this trivially in a couple shots.
        thaumasiotes 4y ago
        Considering the guy who made the shot commented "we were amazed we got it in so few shots", taking all day is expected anyway.
spiderice 4y ago
> non-deterministic kick Actually non-deterministic? Or just difficult-to-deterministic? Genuinely curious.
- kadoban 4y ago
  Very likely deterministic if you knew the _exact_ state of both the bullet and the air, but effectively impossible to know and likely not that easy to model correctly even if you did.
  - jakear 4y ago
    So nondeterministic in the same way an electron passing through two slits is.
    - kadoban 4y ago
      I think slightly less non-deterministic than that, because there's at least some way you could know, if you were god.
    - kragen 4y ago
      As far as we know, quantum nondeterminism is real nondeterminism, not just nondeterministic because you don't know the exact state of both the electron and the slits. Presumably the Navier–Stokes chaos of turbulent flow will eventually amplify quantum fluctuations (where two molecules do or don't interact) into macroscopically divergent fluid dynamic behavior, but I don't know if the relevant Lyapunov time is short enough to make a bullet's flight quantum nondeterministic.
    - cli 4y ago
      I doubt it. The bullet movement may be chaotic, which means that tiny changes in initial conditions will drastically affect the trajectory, but it is theoretically possible to predict the trajectory. However, it is likely that quantum effects such as the movement of an electron through slits is actually non-deterministic, so we can only predict it in a statistical way even in principle.
- 4y ago
wing-_-nuts 4y ago
>Also the when the bullet drops from supersonic to subsonic speed, there is a non-deterministic kick that it receives which dramatically reduces accuracy beyond that distance. Fun fact, while video games typically depict suppressors as slowing bullets down, and lowering range (presumably with subsonic ammo). A lot of rifles are actually have slightly longer range with a suppressor and standard ammo because it allows the powder to burn more completely with a slightly higher muzzle velocity and therefore it takes longer to hit that subsonic transition
thaumasiotes 4y ago
> No... slight variations in wind and atmospherics across that distance change too rapidly and significantly to make that viable. This doesn't sound right. If it's true, then the same thing -- slight variations over time in wind and atmospherics across a seven kilometer span -- would make the aimed shot nonviable too. The shooter isn't adjusting for air movement between himself and the target -- because that can't be done -- so if he's hitting the target reliably, the air movement can't really matter.
- thatguy0900 4y ago
  He's not hitting the target reliably, it took more than 60 tries, and would take just as many to do again
  - thaumasiotes 4y ago
    What's supposed to be impressive about "I hit a bullseye by coincidence"?
    - bell-cot 4y ago
      Impressive that they were able to control things well enough that it only took 69 tries. (Vs. 69,000 or so.) (Yes, statistical "proof" that it wasn't 10,000-to-1 luck would require far more experimental data. With their setup, that wouldn't be quick or cheap to get.)
      - thaumasiotes 4y ago
        > Yes, statistical "proof" that it wasn't 10,000-to-1 luck would require far more experimental data. With their setup, that wouldn't be quick or cheap to get. Saying that this wouldn't be quick or cheap to get is just an admission that you think it was 10,000-to-1 luck. Why wouldn't it be quick?
        bell-cot 4y ago
        Read the article more carefully. Their hugely customized "gun" was only capable of 1 shot every 2 or 3 minutes (to limit heating and thermal expansion ). They had 5 spotters near the target, watching where every individual bullet landed. (Then reporting back to the shooter, so he(?) could make little adjustments.) And it sure looks like an amateur group of "extreme" performance enthusiasts - so who would pay for the collection of a large (say, n=25,000) data set? From a quick web search, just the ammunition (.416 Barrett) would cost ~$400,000. The barrel of their extreme-performance "gun" might need replacing a dozen times or more, and...

spywaregorilla 4y ago

ok wind aside, if that's true, how is it possible to aim it then? It can't possibly be true that you can precisely adjust your aim to hit a specific target if you can't even hit the same target by not changing your aim?

msherry 4y ago
That's why this is such an impressive achievement!
- hamburglar 4y ago
  It’s also why they succeeded on the 69th try instead of the 2nd.
  - thaumasiotes 4y ago
    But that means the approach described above works perfectly. Fire the gun. Place a bullseye over the bullet hole. Then keep firing the gun until you hit the bullseye "again".
    - deleted 4y ago
      [deleted]
    - hamburglar 4y ago
      Well, if you consider that "perfectly," yes, but it could take all day. The ancestor post seemed to be suggesting that if it was so "stable, precise and deterministic" that you could do this trivially in a couple shots.
      - thaumasiotes 4y ago
        Considering the guy who made the shot commented "we were amazed we got it in so few shots", taking all day is expected anyway.

spiderice 4y ago

> non-deterministic kick Actually non-deterministic? Or just difficult-to-deterministic? Genuinely curious.

kadoban 4y ago
Very likely deterministic if you knew the _exact_ state of both the bullet and the air, but effectively impossible to know and likely not that easy to model correctly even if you did.
- jakear 4y ago
  So nondeterministic in the same way an electron passing through two slits is.
  - kadoban 4y ago
    I think slightly less non-deterministic than that, because there's at least some way you could know, if you were god.
  - kragen 4y ago
    As far as we know, quantum nondeterminism is real nondeterminism, not just nondeterministic because you don't know the exact state of both the electron and the slits. Presumably the Navier–Stokes chaos of turbulent flow will eventually amplify quantum fluctuations (where two molecules do or don't interact) into macroscopically divergent fluid dynamic behavior, but I don't know if the relevant Lyapunov time is short enough to make a bullet's flight quantum nondeterministic.
  - cli 4y ago
    I doubt it. The bullet movement may be chaotic, which means that tiny changes in initial conditions will drastically affect the trajectory, but it is theoretically possible to predict the trajectory. However, it is likely that quantum effects such as the movement of an electron through slits is actually non-deterministic, so we can only predict it in a statistical way even in principle.
4y ago

wing-_-nuts 4y ago

>Also the when the bullet drops from supersonic to subsonic speed, there is a non-deterministic kick that it receives which dramatically reduces accuracy beyond that distance. Fun fact, while video games typically depict suppressors as slowing bullets down, and lowering range (presumably with subsonic ammo). A lot of rifles are actually have slightly longer range with a suppressor and standard ammo because it allows the powder to burn more completely with a slightly higher muzzle velocity and therefore it takes longer to hit that subsonic transition

thaumasiotes 4y ago

> No... slight variations in wind and atmospherics across that distance change too rapidly and significantly to make that viable. This doesn't sound right. If it's true, then the same thing -- slight variations over time in wind and atmospherics across a seven kilometer span -- would make the aimed shot nonviable too. The shooter isn't adjusting for air movement between himself and the target -- because that can't be done -- so if he's hitting the target reliably, the air movement can't really matter.

thatguy0900 4y ago
He's not hitting the target reliably, it took more than 60 tries, and would take just as many to do again
- thaumasiotes 4y ago
  What's supposed to be impressive about "I hit a bullseye by coincidence"?
  - bell-cot 4y ago
    Impressive that they were able to control things well enough that it only took 69 tries. (Vs. 69,000 or so.) (Yes, statistical "proof" that it wasn't 10,000-to-1 luck would require far more experimental data. With their setup, that wouldn't be quick or cheap to get.)
    - thaumasiotes 4y ago
      > Yes, statistical "proof" that it wasn't 10,000-to-1 luck would require far more experimental data. With their setup, that wouldn't be quick or cheap to get. Saying that this wouldn't be quick or cheap to get is just an admission that you think it was 10,000-to-1 luck. Why wouldn't it be quick?
      - bell-cot 4y ago
        Read the article more carefully. Their hugely customized "gun" was only capable of 1 shot every 2 or 3 minutes (to limit heating and thermal expansion ). They had 5 spotters near the target, watching where every individual bullet landed. (Then reporting back to the shooter, so he(?) could make little adjustments.) And it sure looks like an amateur group of "extreme" performance enthusiasts - so who would pay for the collection of a large (say, n=25,000) data set? From a quick web search, just the ammunition (.416 Barrett) would cost ~$400,000. The barrel of their extreme-performance "gun" might need replacing a dozen times or more, and...