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-   -   Any ballistics experts? How about this projectile? (http://www.firearmstalk.com/forums/f14/any-ballistics-experts-how-about-projectile-89597/)

Iony123 04-26-2013 06:22 AM

Any ballistics experts? How about this projectile?
 
My question is about a projectile described below?

Most probably, it is a fragment from a bullet. I have data for the first 143.8 milliseconds:

time | vel/fps | range_ft | height_ft | RPM
5.2 | 137.8 | 0 | 0 | 11228
30 | 126.6 | 2.9 | 3.1 | 10145
36 | 123.9 | 3.5 | 3.9 | 9884
42.1 | 121.1 | 4.2 | 4.6 | 9617
48.5 | 118. | 4.8 | 5.3 | 9338
55 | 115.3 | 5.5 | 6.0 | 9055
91.3 | 98.8 | 8.9 | 9.8 | 7471
99.5 | 95.1 | 9.6 | 10.5 | 7113
108.2 | 91.1 | 10.3 | 11.3 | 6733
143.8 | 75 | 12.9 | 14.1 | 5180


time - in milliseconds, projectile starts at time 5.2 milliseconds.
vel/fps - velocity in feet per second
range_ft - horizontal range from origin
height_ft - vertical distance from ground for a given time
RPM - revolutions per minute

Its initial angle is 34 degrees, as measured between the ground and its path upward.
The size is less than 0.19 inches, as a comparison BB shot is about 0.18 inches, 17hmr round is 0.17 inches in diameter
No weight given


This can be computed from above:
- speed deceleration is 453.1 feet per second_squared
- rotational deceleration is 2618182 rotations per minute_squared
- theoretically on the basis of basic formulas, the projectile will totally lose its linear speed after 0.30 seconds
and distance 20.96 feet, and it will totally lose its rotational speed after 0.26 seconds and distance 20.46 feet,
as measured from its origin.

From a practical view, how far such a projectile would fly and how high?

Are the decelerations high enough to suggest that the projectile has very low ballistic coefficient (BC),
that the projectile is an irregular fragment broken away from a bullet.

c3shooter 04-26-2013 10:03 AM

I know of no bullet that has a muzzle velocity that low. Assuming construction of ordinary materials, try to see how far you can throw a single pellet of birdshot by hand.

Colby 04-26-2013 10:43 AM

I mean no offense, but this seems like a silly question and set of figures.

The object is very small, starts out at 94 mph, drops what little speed it has very quickly, has a very short range (20 ft), has a very shallow rise (only a matter of a little over the described 14 ft - say 20 feet). This could described many objects - but not a bullet.
The only unusual thing about the set of numbers is the high rotational speed - compared to the rest of it's low energy components. The rotational speed does not seem to match up to the rest of the objects ballistics. 11,000 RPM is pretty high rotation and requires a good bit of relative energy to impart that rotational inertia. But the rest of the ballistic numbers describe an object with very little energy. Hence, the numbers don't seem compatible - in normal life. Not saying it is not possible - but not likely. Seems like made up stuff. But why? What is this about? And who cares?

Don't know where you got these numbers, but I wouldn't spend a great amount of time working with them. The intitial speed is slower than a high schooler's baseball pitch.

JohnJak 04-26-2013 12:41 PM

Way above my mentality.

Iony123 04-26-2013 11:18 PM

Thanks for replying.

The included table has one wrong column. Ignore the column showing height because I included it by mistake. Just use the initial velocity and deceleration constants to compute the range and times, and the angle to compute the height.

The decelerations are constants because they are approximations. I have two images of this projectile and by computer simulation I was able to extract the best deceleration constants. Keep in mind that the data are based on the initial 143 milliseconds (0.143 second) so everything is close to a straight line,

As far as low rpm, keep in mind that this projectile went through a body, so it lost most of the rotational velocity in addition to linear velocity before it exited with the parameters shown. I am trying to figure out what it could be. The bullet is an incendiary type, with something like White Phosphorus (WP). Look up the bullet B Patrone. It has a nose with WP and a little explosive booster. Once it hits an object like a body it gets fragmented and apparently some of it created a projectile.

SSGN_Doc 04-27-2013 12:04 AM

Mine shrapnel?

c3shooter 04-27-2013 01:28 AM

My crystal ball is in the shop for calibration- you are feeding us dribs and drabs of information- some of which simply does not make sense taken on its own.

There is a good bit of knowledge around here, but give us what you have, and photos. We are kind of wandering in the dark here.

You are speaking of a rotational speed- but from a bullet fragment? Fragments generally cease rotation once the projectile breaks apart- centrifugal force throws them in different directions. The B Patrone in 8mm Mauser is actually an observation cartridge. Flash/ puff of smoke on impact to spot the strike of the round.

Tell us what you know, we'll share what we know.

SSGN_Doc 04-27-2013 01:44 AM

Yes, some context would be nice. If you already know that the projectile went through a body, then it would be likely that there are other bits of information to be shared.

BeyondTheBox 04-28-2013 04:39 AM

I really don't know ballistics well at all but could it be a BB, or one of those 6mm plastic beeds from a spring operated airsoft gun? That low of velocity seems odd, unless I'm not reading it right, which wouldn't surprise me at all. Lol just a thought.

Vikingdad 04-28-2013 04:52 AM

Higgs boson?


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