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Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons, particularly in larger calibres (12.7+mm).

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Energy vs. Momentum   General Military Discussion

Started 5-Aug by JesseH1234; 3288 views.
QuintusO

From: QuintusO

8-Aug

EmericD said:

At a time, the US Army used an interesting criteria which was M.V^(3/2) [so, midway between momentum and kinetic energy]. I think that the idea was that penetration (for non-deforming bullets) is a function of M.V^(1/2) / S [M being the weight, V the velocity and S the frontal area] and material displacement is proportional to S.V (big frontal area and high speed means more instantaneous displaced materials during impact). So, if you "integrate" the instantaneous volume displaced by the bullet along it's path, you end up with something proportional to M.V^(3/2).

I think it's best not to confuse the boy further.

QuintusO

From: QuintusO

8-Aug

You're attempting to criticize previous approaches to the problem, which is good. The fundamental flaw in what you're doing is that it's very evident you don't really understand the math behind the physical phenomena we're talking about. What you've written here (evidently) demonstrates the following shortcomings in your approach:

-You do not know the difference between an elastic and an inelastic collision (equating hitting plates with penetration dynamics, e.g., penetrating a living target)
-You don't seem to be aware of the difference between lbs mass and lbs force. 
-You appear to be completely clueless about what kinetic energy is, what it measures, and even what factors are involved in its computation

And I could go on.

My point is, the criticism of previous approaches is welcomed. However, there's a massive education gap here. It's important that before you approach this subject, you go out and get a solid understanding of newtonian physics at minimum, which you currently do not have. That's it, that's my piece.

DavidPawley

From: DavidPawley

8-Aug

I’m a physics teacher. I’ve been keeping out of this thread since correcting your errors is work not a hobby.

However, you might find these simulations useful in correcting your misconceptions.

https://phet.colorado.edu/en/simulation/forces-and-motion-basics

https://phet.colorado.edu/en/simulation/energy-skate-park-basics

In reply toRe: msg 19
JesseH1234

From: JesseH1234

9-Aug

JesseH1234 said:

I am aware of other design considerations and I am not arguing we return to .80 caliber musket balls. I'm not arguing anything other than pointing out that pointing to "energy" in a vacuum does not mean a whole lot. I went down this road in my head asking myself why 5.7 hasn't blown all other autopistol calibers out of the water; I ascribed it to just the archaic nature of the gun world, but when I saw someone hitting plates with a 5.7 and then a 9mm a big ol question mark appeared. That's it.

Yall can poke fun all you want, but I feel I now have a very clear understanding of how the on-paper high school physics values translate into real-world effects in the context of firearms.  As imperfect as my question was, somehow Emeric understood what I meant and gave an actually insightful answer. 

To Certain Persons: let me explain something about how learning works.  You never, ever learn anything by reinforcing how "right" you were from the beginning; that is a dopamine release hard wired into you, a trick played on you by evolution.  You only learn by being wrong.  A fun and effective way to do that is to stake out an intentionally exaggerated position, and let people poke holes in it.  If you are savvy, you will be able to sort the knuckle draggers from the wise pretty easily.  You sort through the dust kicked up by the former, and look for the gems left by the latter.  The "truth" is often a complex and nuanced thing, rarely reducible to a single variable, and this is hard for 99.9% of humans to grasp. 

JesseH1234

From: JesseH1234

9-Aug

stancrist said:

IMO, your biggest flaw is trying to oversimplify the matter by comparing military cartridges on the basis of relative power, regardless of how "power" is defined. There are so many factors that are much m

I actually totally agree, "power" was in quotations because I lacked a better word.  It really was a question.

DavidPawley

From: DavidPawley

9-Aug

So your “intentionally exaggerated position” was to totally misunderstand energy as the ability to do work. Gotcha.

JesseH1234

From: JesseH1234

9-Aug

Excellent strawman, Poindexter. 

QuintusO

From: QuintusO

9-Aug

Yeah, you actually don't have a good understanding of the physics at all going by your most recent posts.

But, message received. You don't want to learn, you just want Good Feelings only, and I know how much learning hurts!

DavidPawley

From: DavidPawley

9-Aug

It's not actually a strawman fallacy when you put the words in your own mouth.

Anyway, like I said, work not hobby, so knock yourself out.

Before I leave you to it though, one question;

How do you feel about barn owls?

JesseH1234

From: JesseH1234

11-Aug

Feel free to never respond to anything I post, ever.  I am totally and completely uninterested in your input, but we both know that you will give it anyway. 

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