WW2 Air Combat Footage: Squiggly Gunnery Footage

[rabbidrabbit]

Bad wording on my part.  It is one rev per foot but it's not traveling at one ft per second is what I'm saying.  Thus, it's spinning quite fast.

[LCADolby]

https://www.youtube.com/watch?v=Qhm7-LEBznk

I could have soo much fun with that. I'd not be able to stop all day. 

[Motherland]

Bad wording on my part.  It is one rev per foot but it's not traveling at one ft per second is what I'm saying.  Thus, it's spinning quite fast.

you're not seeing the round spin, you're seeing the path it leaves, by way of the smoke. It doesn't matter whether it leaves that path at 1 f/s or 3,000 f/s or the 300,000 f/s. There will still be one complete spiral of smoke every foot.

[phatzo]

you're not seeing the round spin, you're seeing the path it leaves, by way of the smoke. It doesn't matter whether it leaves that path at 1 f/s or 3,000 f/s or the 300,000 f/s. There will still be one complete spiral of smoke every foot.

prezactly

[MrRiplEy[H]]

I'm not sure I'm following you.  One revolution per foot would be true if it were traveling at one foot per second.  It's not.  It's traveling at 3000 ft per second.  Thus, is rotating 3000 times per second.  There will be a variance based on twist rate and muzzle velocity but even taking half the 3000 turns per second it is still spinning 1500 times every second.  How do human eyes see the revolutions as a corkscrew going through the air?  It would be spinning way too fast to see without reviewing via a high speed camera.   

I'm all for the effect, it looks cool but I'm not certain your explanation works.

What am I missing?

It's spinning exactly one revolution per foot as it travels 3000 feet per second and rotates 3000 times per second. The rifling turns the bullet and the bullet is not going to magically speed up after it leaves the barrel

[rabbidrabbit]

It's spinning exactly one revolution per foot as it travels 3000 feet per second and rotates 3000 times per second. The rifling turns the bullet and the bullet is not going to magically speed up after it leaves the barrel

By the example given, I said it's turning one revolution per ft traveled.  And given a muzzle velocity of 3000 ft per second it's turning 3000 times in that second.  No one, other than you, said it was some how speeding up after leaving the muzzle.  My point was that if it's turning that fast, the spiral you see in the video does not make sense.  Watch the video and count the rotations over one second and tell me what count you get.

I must be neglecting to include the treadmill effect but unless my count is off, those rounds are turning a lot less than 3000 times per second.

[Motherland]

By the example given, I said it's turning one revolution per ft traveled.  And given a muzzle velocity of 3000 ft per second it's turning 3000 times in that second.  No one, other than you, said it was some how speeding up after leaving the muzzle.  My point was that if it's turning that fast, the spiral you see in the video does not make sense.  Watch the video and count the rotations over one second and tell me what count you get.

I must be neglecting to include the treadmill effect but unless my count is off, those rounds are turning a lot less than 3000 times per second.

It makes perfect sense, because it's spinning at the same speed that it's moving.

[MrRiplEy[H]]

  Watch the video and count the rotations over one second and tell me what count you get.

We would first need to know the framerate the video was filmed at. If it's filmed at high fps the rotations will appear naturally to be much slower.