Great Video on Ballistics by Lucky Gunner!

[the Schwartz]

Traditionally, that parking space is reserved for buses full of nuns and orphans.

Oh, you are horrible! But...I like it! I like it!

Yeah......'gallows humor' is my thing.

[RJ]

As I was digging through some of the research material that I have amassed throughout the years, I came across this one (see attached)― Non-Newtonian Behavior of Ballistic Gelatin at High Shear Rates, Experimental Mechanics (2012) 52:551–560. I thought that you might like to see it.

Attachment 37318

In the attached paper there is a simple power law that allows for the adjustment of dynamic viscosity at high shear rates which is really useful for calculating Reynolds Numbers (R_e = ρVD/μ) for high-velocity penetration events in the 10^-4 seconds range. The coefficients for the power law were fitted against the empirical data using the 'least squares' method.

The equation is:

μ = αγ^(n-1)

where μ = dynamic viscosity in centipoise (cp) for 10% gelatin
γ = shear strain rate in s^-1
α = 4.5 x 10^-3 kg∙s^(n-2)
n = 2.22

As stated in the paper above, when the dynamic viscosity for a projectile is calculated for shear strains of 2,000s^-1 and 8,000s^-1, dynamic viscosity increases about 5 times as shown below:

4.5 x 10^-3 kg∙s^(2.22-2) x 2,000s^-1(2.22-1) = μ = 3,243 cp

4.5 x 10^-3 kg∙s^(2.22-2) x 8,000s^-1(2.22-1) = μ = 17,598 cp

Of course, the Q-model can be used to compute such time frames.

For the latest test that I conducted here: https://pistol-forum.com/showthread....slug-(P152XT1) ―

―the computed duration for that test was on the order of 4.858 milliseconds, so dynamic viscosity would have been on the order of―

4.5 x 10^-3 kg∙s^(2.22-2) x 2,058s^-1(2.22-1) = μ = 3,716 cp

―which means that the average Reynolds Number (R_e = ρVD/μ) for this event would be R_e = 29.211 indicating that turbulence would be very low since R_e < 2,000.






ETA: This paper might also add some valuable insight:

Attachment 37324

Ho Lee Frack.

Been a while since I used stuff like this.

Are you now or have you ever been a Materials Science Engineer or ChemE? Cause those were the only guys I knew in Tool School who could whip out a sub-2,000 Laminar flow Reynolds Number* with a straight face.

*Dear God I hope I’m remembering that right. Good thing I took up EE. Electrons are much easier lol.

[the Schwartz]

Ho Lee Frack.

Been a while since I used stuff like this.

Are you now or have you ever been a Materials Science Engineer or ChemE? Cause those were the only guys I knew in Tool School who could whip out a sub-2,000 Laminar flow Reynolds Number* with a straight face.

*Dear God I hope I’m remembering that right. Good thing I took up EE. Electrons are much easier lol.

Unfortunately, it was not a laminar flow that was actually computed as I misplaced the decimal in my haste to post.

It should have read as:

―which means that the average Reynolds Number (R_e = ρVD/μ) for this event would be Re = 2921.1 indicating that turbulence would be significant since Re < 2,000.

Not and MSE or ChemE, though I do have a post-grad in a related field.

[Jay Cunningham]

Moved to Romper Room.

[BBMW]

Okay, maybe my sarcasm was just a touch too subtle.

Really?

The answer is quite obvious...

[Tamara]

Okay, maybe my sarcasm was just a touch too subtle.

What was the point that was missed?

[BBMW]

You're quote basically said that the only things that counted were shot placement and penetration. Since basically no LE organization use FMJs as carry ammo, they don't follow your reasoning.

What was the point that was missed?

[Tamara]

You're quote basically said that the only things that counted were shot placement and penetration. Since basically no LE organization use FMJs as carry ammo, they don't follow your reasoning.

If we're assuming all dudes are spherical and we're shooting them in a frictionless vacuum, it is. (In a world where overpenetration is an actual thing, it's not.)

There's also esoterica about meplat shape and stuff like that and its effect on wound channels, I suppose.

I'll say this, though; once upon a time I would have been filled with anxiety if I'd accidentally shot up my carry ammo on the first day of a class and had to brave the terrors of the Holiday Inn Express parking lot on Saturday night with a magazine full of FMJ, but the more I've read about this stuff... well, I really don't sweat that sort of minutia anymore. ¯\_(ツ)_/¯

[spinmove_]

If we're assuming all dudes are spherical and we're shooting them in a frictionless vacuum, it is. (In a world where overpenetration is an actual thing, it's not.)

There's also esoterica about meplat shape and stuff like that and its effect on wound channels, I suppose.

I'll say this, though; once upon a time I would have been filled with anxiety if I'd accidentally shot up my carry ammo on the first day of a class and had to brave the terrors of the Holiday Inn Express parking lot on Saturday night with a magazine full of FMJ, but the more I've read about this stuff... well, I really don't sweat that sort of minutia anymore. ¯\_(ツ)_/¯

Honestly, I have to agree. Shot placement and adhering to the 4 safety rules (including that one that says something about knowing your target and what is beyond/in front of it) are more important than your ammo. Bullets can do funny things sometimes and you can’t always count on even the best JHPs performing exactly how you expect them to.

Definitely don’t stop carrying good quality JHPs as they’re far and away your best option. But there’s plenty of people who’ve been put in the ground with FMJs. There have also been times when JHPs have plugged and either didn’t penetrate deep enough or way over penetrated.


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[BBMW]

Maybe you should be using the FMJs on the range, and keeping the better quality hollowpoints for carry. If nothing else, it's cheaper that way.

The think is, when you need your pistol to put down a BG, you REALLY need it to put down he BG NOW!!! FMJ is the ammo that's least likely to do that, everything else being equal (and there's nothing about using FMJ vs better hollowpoints that would not make everything else equal.)

If we're assuming all dudes are spherical and we're shooting them in a frictionless vacuum, it is. (In a world where overpenetration is an actual thing, it's not.)

There's also esoterica about meplat shape and stuff like that and its effect on wound channels, I suppose.

I'll say this, though; once upon a time I would have been filled with anxiety if I'd accidentally shot up my carry ammo on the first day of a class and had to brave the terrors of the Holiday Inn Express parking lot on Saturday night with a magazine full of FMJ, but the more I've read about this stuff... well, I really don't sweat that sort of minutia anymore. ¯\_(ツ)_/¯