Bullet drop formula?

[x SF med]

... When a good looking guy is turned into a troll by a witch (Chops). It makes all the much more neater for the witch when the victim remembers what they were like. Another reason not to mess with the Witch.

Nope, always been a Troll... except for the two occasions when witchipoo turned me into a newt... I'm taken aback at your insinuation that Trolls are of below average intelligence... your prejudice is showing and this is disturbing to me that I drink beer with such a bigot.... where's the friggin bottle opener and seared animal flesh?

 

[Turtle]

Face it, Troll IS a ballistic computer

 

[HOLLiS]

Nope, always been a Troll... except for the two occasions when witchipoo turned me into a newt... I'm taken aback at your insinuation that Trolls are of below average intelligence... your prejudice is showing and this is disturbing to me that I drink beer with such a bigot.... where's the friggin bottle opener and seared animal flesh?

This weekend, seared flesh, beer and shooting these:

 

[Totentanz]

Okay... I give up... I out geeked the math geek.... I am ruined and should go into hiding.:eek:

LOL, when it comes to ballistics and the surrounding physics... you got me there.

H: I trust ballistics calculators, but I'm not really interested in just computing dope. I want to actually understand why a bullet stabilizes with a certain velocity and twist, why it behaves the way it does when it goes subsonic, why one ogive is better than another, etc. Most rigorous collegiate-level physics texts (at least the ones I've come across, hence the question) don't want to address those questions in a real-world manner without their assumptions.... and I'm skeptical of most internet sources.

FWIW, I did find this page (http://www.jbmballistics.com/ballistics/topics/topics.shtml), which seems to be in the ballpark and grounded in reality.

 

[Etype]

You seem to have researched this a bit, so if my redneck explanation is insulting, consider it intended for the other people.

A bullet will fly well in supersonic flight and in subsonic. Whitworth rifles, 40mm rounds, etc. are examples of pretty darn accurate subsonic rounds. It's the subsonic realm that destabilizes a bullet.

Two good terms to understand-
Transonic- when there is a variation of velocities around the bullet, some of the air is supersonic, some of it is subsonic. Think of the Supersonic 'wave' (that you see as trace) catching up to the bullet and flowing across it.

Wave Drag- Shock waves created by air moving at supersonic speed around or near a non-supersonic object. (someone help me out if you have a better definition)
How does this effect a bullet? During transonic flight, air moves fastest around the largest part of the bullet (venturi effect, maybe?), however, it slows down to below the speed of sound before it reaches the rear. Since the whole bullet is not moving at the speed of sound, the supersonic shock wave effects the rear of the bullet and induces wobble/tumbling.

Nutshell non-scientific explanation-
The sonic boom that you hear from a supersonic bullet (or jet) is all the sound (or energy from the bullet pushing the air apart) compressed until all the sound waves are stacked on top of each other. Since the bullet is moving faster than the speed of sound, they stack up (really they are just sound waves that are very close together). That 'stack' of compressed air and sound has a lot of energy, anyone who's had supersonic rounds fired right over their head (think the pit at a sniper range) knows this from the sound- that little bullet makes a lot of noise.

During transonic flight, which I believe covers less than about 200m of flight, all of that energy sweeps back across the round from rear to front (think the cool videos of fighters breaking the sound barrier, except in reverse). This is what causes a supersonic bullet to wobble in transonic and early subsonic flight, and eventually tumble. Luckily, it happens somewhat predictably and we can obtain data on the range and on good systems like ATrag, however it's nowhere near as consistent as supersonic flight.