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All we need is a decent estimate of how high it went and how many frames it took to go up and back down. Nothing else to make anyone crazy because nothing else matters. Either it went in a parabola in Earth gravity or it didn’t.
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It looks fairly parabolic in the enhanced images. it is very hard to define the path in the original images, what can be made out does match up. I will redo the gif image soon to fix up the errors, will also add in a path to help see the casting trail.
But we can do some high school physics for fun.
So I choose uniform distribution between 0 and 1/60.
The average value is 1/120, we take the square.
∆y = 16 * (1/120)^2 = 0.0011…
So the expected error is omly 0.11% would be.
Now we haven’t finished yet. We need to know the deviation. I must think…
I am all for the answer supporting whatever it supports. But once the casing leaves the gun, it must obey physics based on Earth gravity. If it reached a maximum height 9 inches above the ejection port and then fell 12, here is the height where it would be found at every frame, with 0 = ejection port height, (but don’t forget KINCSES half-frame uncertainty):
If it had to fall much further, it would be doing that quickly, so max 1 or 2 more frames before it bounces even if we get the drop to the roof wrong.
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Watch 20 seconds of the first video from this post here after you press play, on the other thread.
It’s a video from the Rifle World Shoot some weeks ago. Side camera is a bit dark, but you’ll see the shells going all over the place. Does it look like you can get a ‘decent estimate’ out of this inconsistency?
I don’t even have to look. I don’t care at all whether they go forwards, sideways, or backwards, or how far out they eject. Their VERTICAL path will always follow a parabola based on Earth gravity. You may completely ignore the horizontal component.
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Actually it was almost a real task in my life.
A machine makes 65 rounds every minute. Bullets weight must be measured on digital scale. How many samples the scale must take? (There was a guess by an old man: 10 sps)
Spoiler: we did not calculate the standard deviation and the uncertainty. Our expert said: the worst case error must be small enough.
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I hope that didn’t come off flippant. If the casing came out near horizontal or barely rose at all, it might be more difficult to check the physics at this distance. But this one went spinning in a cute little upwards path perfect for a photo op, so we may as well make sure the physics works.
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Thanks for your calculation. I don’t know much about ejected castings physics and how standard this model is across all guns. Appears that there is some variation in gassing pressures that kick out casting, even among the same model guns depending how it is setup and how worn out it is getting. Does this make much of a difference?
Did shot #9 really damage the rifle? As an excuses to not test fire it as see how it really handles? Maybe it did really get smashed up, no more shots after that. Have not been able to identify any significant damage with the gun images released so far. The crowd reaction from shot #10 was the one that let the crowd know it was game over.
Ok, so you guys are going to add even more uncertainty to the already uncertain approach of using video frames to check a distance we already have? So now we would not only have the uncertainty of the video compression dropping frames, the gas tube math that needs checking, but now also the geometry and physics of flying shells using statistical analysis and probability?
@kwaka before you unleash this monstruosity of a task on @kincses-zsolt and @offtheback , maybe could you send us more of what you got so far regarding your approach to use the distance to check if that sound matches that shell ejection, if I got your approach correctly?
I haven’t seen a lot of guns tossing them upwards this much, but I don’t claim to have paid attention either. And even shot-to-shot they flip out differently.
But none of that matters here. All we have to do is take a video of one casing’s journey into history–one that just happened to be tossed up, and make sure it agrees with gravity and is at least authentic in that respect.
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No. i am doing it to check the source material that we have to work with. The distance is clear between all the maps. What is not clear is why there is a 5 frame discrepancy between the audio and video track. Maybe it it nothing, an innocent mistake, maybe it is something. As part of an audio analysis it is fitting to ask these kinds of questions.
I have sent TMZ a message outlining this problem. If they send me an email I will let the board know.
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I want to cite R. Feynman: “You don’t like it, go to another Universe.”
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Thank you Kincses, for the inspiring punchline… I’ll be in the kitchen with my measuring tape and some popcorn… I’ll try to measure how high they pop.
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That’s the muzzle velocity that works out with the parameters I used. I know it’s rather lower than most ammo and AR-15 type rifle combinations. Everyone is welcome to check my numbers. I found I’d made a pretty big mistake yesterday, and wish someone else had caught it first.
The weird thing is, many of us that are thinking the first 3 shots came from the vent of AGR building 6, while shots 4-8 came from Crooks. If my numbers are right, with a snap-bang time of only 0.213 seconds, that muzzle speed for Crook’s rifle would need to be even slower - around 2570 fps.
As far as your sample values, if the velocity at 150 yards is 85% of muzzle velocity, I’d guess the average velocity is a little less than the arithmetic average of 85% and 100% - say 91% or 92%. It worked out to about 94% for one sample I used.
I should probably round the numbers (or specifically show what I think the upper and lower limits might be) to not give the impression they are more precise than they really are.
Uh oh! Richard Feyman reference!
I mentioned elsewhere I’m a Caltech washout. I’m old enough that Professor Feynman was a professor at Caltech while I was a student (1982-1984). In addition to his normal duties, once a week he would host a session called Phys X, where people would just ask any question they wanted.
A lot of freshmen loved to go to this. I’m sure some kids wanted to ask questions that would make them sound really smart. I only went once, and didn’t ask any questions.
Afterwards, my OTHER best friend (not Tsutomu Shimomura) asked Professor Feynman if he would play the bongos at Phys X some time. Prof Feynman said he didn’t think so. I was standing next to my friend at the time. So I kind of, sort of, met Richard Feynman.
This guy had a real fan base at Caltech, let me tell you.
If you watch the movie “Oppenheimer” you will see Richard Feynman portrayed in a few snippets here and there. He is shown playing the bongos in one scene in Los Alamos at Christmastime. In the scene where they detonate the test bomb he’s the guy behind the car windshield saying the windshield should be enough to protect his eyes. In the Caltech alumni facebook group people were talking about that kind of stuff quite a bit after the movie came out.
Anyway, if you look up Tsutomu Shimomura’s wikipedia page, it will say he studied under Richard Feynman at Caltech. What that means is he went to at least one of those Phys X seminars. I think he also sat in on a few actual grad level physics classes Feynman was teaching, but he didn’t enroll in any of them. Tsutomu lasted a year longer than I did, but didn’t end up graduating from anywhere. He’s smart enough and has good enough connections he’s done pretty well for himself anyway. After all, his dad won a Nobel freaking prize. My dad worked at the post office.
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Maybe some reloads instead of factory ammo? But at those speeds, you might want to try an online ballistic table for 77 grains ammo (I use Hornady’s calculator). For instance, manufacturer CBC Global has the following values for their 77 grains 5.56x45 ammo:
Ballistic coefficient of 0.362
Distance (m) - m/s - fps
Muzzle - 850 - 2790
100m - 767 - 2541
200m - 689 - 2305
300m - 616 - 2081
Test barrel: 50cm - 19.68inches… (Crooks might have used a shorter barrel, say 16", which would give a little less velocity).
Ah yes, sorry, the 94% you’ve been using is the average, and not the velocity at the target’s distance.
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How about practically? Guess who just learned how to make GIFs? 
I guess we finally have moving hair afterall. We can see his skin when recoil splits his hair. Or light reflecting due to motion, but still, motion nevertheless. While a casing if flying, his shoulder is moving (just a little, his proned body weight acting against the recoil and all), and a head tilt (this one is easier seen on the video editing software going back and forth with the keys, I must admit)
So I’ve decided to install video editing software afterall. Thanks for the ShotCut info, @kwaka. Please take a look at this image above. Is this similar to what you got on your timeline?
I’ve called my frames as such because I didn’t want my count to start at zero, so I just arbitrarily picked 30 as the frame where I see the casing better, so I counted back and forward, assigning frame numbers. This filters here are stabilize, size, that timecode one and sharpness. The video is a direct download from the TMZ website using 💾 Download and Save TMZ.com videos: Quick & Free, No Installation!. The start of the video is point zero on the timeline.
frame 27 - no visible alteration on shooter
frame 28 - shot and shooter feels recoil - hair ‘enlarges’
frame 29 - casing not visible, but must be ejecting - head tilts
frame 30 - casing is clearly visible
frame 31 - casing is clearly visible - hair splits visible
frame 32 - casing - head going forward
frame 33 - casing
frame 34 - casing
frame 35 - casing
frame 36 - casing seen for the last time
frame 37 - casing obstructed view - no sound of shot yet
frame 38 - shot sound is heard for the first time. has already reached the microphone at this frame.
Another thing, when I switch Google Earth to 2D the distance from shooting place to the trunk of the tree, where the tmz video was recorded from, I get 290 feet… closer, but still no cigar.
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ALL
For info, the guy at Peak Tactical has been out to Site and taken accurate GPS readings and heights (above sea level.) He’s putting that into a 3d terrain map (held by others.) Which is going to be accurate so thought you should be aware.
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