Bullet stability

[RockyMtnMT]

Barrel length is a factor in muzzle velocity.

Correct, but MV does.

Regardless of the bullet stability calculator used, i.e., as provided in #11, factors affecting SG are already provided. Any changes in one of those attributes will affect the SG. Don't overcomplicate it unnecessarily.

I know bullet X manufacturer will claim their ballistic/SG apps will not work because of their bullet design. Most bullet manufacturers, i.e., Sierra, Berger, Hornady, etc., have their "ballisticians" that are subject matter experts in the field that can help you better understand if you want to go that route.

Cheers!

Can you define a ballistician? What qualifies one to be a ballistician? Is there an actual degree for being a ballistician? What does a ballistician do that you wouldn't do to find the answer to a ballistics question?

 

[Hugnot]

Can you define a ballistician? What qualifies one to be a ballistician? Is there an actual degree for being a ballistician? What does a ballistician do that you wouldn't do to find the answer to a ballistics question?

A person who has a degree in engineering/physics/math & likes bullets. Bryan Litz qualifies.

Possibly, Fourier Transform of equation for effects like precession exerted on the spinning bullet to come up with a simplification that could be easily solved (I would not do stuff like that because I don't know how). Smart guys present stuff in cookbook form to folks like me for solutions.

 

[Hugnot]

I know this is technically right on. On the other hand we see long for caliber bullets holding sub half moa but then swapping ends at 1300y. Speed still well away from transonic with stability technically getting higher the farther out the bullet travels but then hitting a point the heavier end of the bullet passes the lighter front end. Which is where it wants to be and we stop it from happening by spinning the bullet. There comes a point where dynamic stability trumps ballistic stability and then it is all thrown out on its ear. It is most definitely a head scratcher.

My guess is those long pointy bullets (looking like torpedoes) were never "dynamically stable" and exceeded the Miller parameters for reasonable Sg estimations.

 

[Mike Matteson]

Following! The only problem I have is: Adding 2+2 and coming up with 3. Interesting reading, but above my pay grade.

 

[Seabeeken]

What do you mean [exactly] by 'marginally stable' for that scenario?

I mean that the calculator referred to it as marginally stable at 1.48 at 3000 fps. At 3300 fps, it referred to it as stable at 1.51.

 

[scpaul]

I feel stupid even asking this but, did I understand you to say that downrange at a point where the bullet rotation decreases sufficiently that the heavier base wants to pass the lighter front. Would a bullet shaped like a somewhat pointed teardrop do any good instead of fighting the reversal down range? That is firing the larger heavier end first. That seems crazy.

 

[RockyMtnMT]

I feel stupid even asking this but, did I understand you to say that downrange at a point where the bullet rotation decreases sufficiently that the heavier base wants to pass the lighter front. Would a bullet shaped like a somewhat pointed teardrop do any good instead of fighting the reversal down range? That is firing the larger heavier end first. That seems crazy.

Doesn't seem crazy to me. We have tried it unsuccessfully but may visit it again one day.

 

[RockyMtnMT]

A person who has a degree in engineering/physics/math & likes bullets. Bryan Litz qualifies.

Possibly, Fourier Transform of equation for effects like precession exerted on the spinning bullet to come up with a simplification that could be easily solved (I would not do stuff like that because I don't know how). Smart guys present stuff in cookbook form to folks like me for solutions.

I tried looking and the only degree I could find was in forensics. Something like physics maybe. In the end ballisticians dream it up and then go and test it to see if it works. Just like all of us here.

 

[scpaul]

I bet forming a bullet that shape would be a problem atleast according to the big bullet makers. They would probably be worried about acceptance and recouping costs.

 

[Maol]

Not Bryan Litz here; would decreasing the mass in the base/rear area of the bullet not work instead of 'teardropping' it?

 

[xsn10s]

Degrees for ballistics depends on whether you want a study on internal, external, or terminal ballistics. For the study of bullets in flight you'd want to study external ballistics. In that area someone with an aerospace engineering degree would be a start. I'd still consider someone with a mechanical engineering degree fine for the bullet arena. If looking for someone with the esoteric knowledge of bullet flight then Bryan Litz would be my choice for knowledge in external ballistics. He's pretty much looked at as the leading expert in the subject. Terminal ballistics would be the study of wounds or bullet impact.

 

[Doom2]

I tried looking and the only degree I could find was in forensics. Something like physics maybe. In the end ballisticians dream it up and t

There are no degree programs in Ballistics. A ballistician is someone who works in the field of ballistics. External Ballistics is studied in physics, aeronautical engineering, and mechanical engineering. Internal Ballistics is more in the realm of Chemist and Chemical Engineers. Bryan Litz is an aeronautical engineer. Jeff Siewert who was on Hornady's Podcast recently has a degree in physics if I remember correctly. Not sure about Don Miller.

The Miller equation is conservative by design and is an empirical formula based on some basic physics. The intent of the equation is to provide the rifle twist rate needed to provide bullet stability not the stability of the bullet. If you are interested this is a link to his paper:

https://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_1.pdf

 

[Wedgy]

Not Bryan Litz here; would decreasing the mass in the base/rear area of the bullet not work instead of 'teardropping' it?

Think of something like a wad cutter shape or a beer can, but not bud light.

 

[scpaul]

I understand that B.Litz is the go to expert on the ballistics subject but isn't there another unaffiliated engineer that could give fresh/different views? Nothing against Litz but if you keep asking the same person similar questions wouldn't you expect similar answers? Believe me, I'm no engineer but just like at 1 time all we needed was B-1 ballistics models. We have learned some things that not so long ago people thought were impossible and have had to come up with a B-7 ballistics model because a projectile with a BC of over 1.0 was thought to be unattainable. I hope that I said that right.