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Old 11-19-2016, 04:32 PM   #21
acrosome
 
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Default Re: What Is This Bullet For?

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Originally Posted by warellis View Post
As for tumbling, hasn't that been disproved and in reality it has been found that bullet fragmentation is what kills?
No.

That idea comes from a paper Fackler published, and has been widely misinterpreted. (It is discussed at length at the link in my sig.) And then the various gun media, blogs, and general know-nothings have argued it back and forth and you'll find it everywhere, right beside "never use a pistol whose caliber doesn't start with a 4" and other nonsense.

Fackler's paper was not trying to, and never stated that, bullet tumble and temporary cavities were immaterial. At the time there was a belief that the lethality of a bullet could be increased almost infinitely by increasing velocity. Or alternately, lethality could be retained at lower weight by pushing smaller projectiles to higher velocities. (This is how we ended up with ridiculous designs like the Steyr ACR flechette gun and other such absurdities.) And this is what Fackler was saying had gotten over-emphasized... and he was correct. His paper merely said that the effects of fragmentation were being overlooked. But he wasn't saying that tumble and temporary cavities weren't a factor! This is why 7.62mm is pretty lethal- it turns sideways and creates a simply gigantic temporary cavity- but it usually exits the target before fragmenting unless it hits bone. This contrasts with the 5.56mm which (with proper loads- another long discussion) would otherwise create much smaller temporary cavities, but which fragments wildly. Both mechanisms work. And they are linked- fragmenting projectiles deliver more energy to the target and tend to develop larger temporary cavities.

Small caliber rounds that are high velocity but stable or otherwise don't fragment do indeed suffer from "ice-picking."

Last edited by acrosome; 11-19-2016 at 04:40 PM.
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Old 11-20-2016, 02:22 AM   #22
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Default Re: What Is This Bullet For?

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Originally Posted by acrosome View Post
No.

That idea comes from a paper Fackler published, and has been widely misinterpreted. (It is discussed at length at the link in my sig.) And then the various gun media, blogs, and general know-nothings have argued it back and forth and you'll find it everywhere, right beside "never use a pistol whose caliber doesn't start with a 4" and other nonsense.

Fackler's paper was not trying to, and never stated that, bullet tumble and temporary cavities were immaterial. At the time there was a belief that the lethality of a bullet could be increased almost infinitely by increasing velocity. Or alternately, lethality could be retained at lower weight by pushing smaller projectiles to higher velocities. (This is how we ended up with ridiculous designs like the Steyr ACR flechette gun and other such absurdities.) And this is what Fackler was saying had gotten over-emphasized... and he was correct. His paper merely said that the effects of fragmentation were being overlooked. But he wasn't saying that tumble and temporary cavities weren't a factor! This is why 7.62mm is pretty lethal- it turns sideways and creates a simply gigantic temporary cavity- but it usually exits the target before fragmenting unless it hits bone. This contrasts with the 5.56mm which (with proper loads- another long discussion) would otherwise create much smaller temporary cavities, but which fragments wildly. Both mechanisms work. And they are linked- fragmenting projectiles deliver more energy to the target and tend to develop larger temporary cavities.

Small caliber rounds that are high velocity but stable or otherwise don't fragment do indeed suffer from "ice-picking."
Which IIRC is the justification for GURPS giving the 5.56 past a certain velocity Pi rather than Pi- which it would other wise get.

Last edited by Tomsdad; 11-20-2016 at 02:31 AM.
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Old 11-20-2016, 03:43 AM   #23
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Default Re: What Is This Bullet For?

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Originally Posted by Tomsdad View Post
Which IIRC is the justification for GURPS giving the 5.56 past a certain velocity Pi rather than Pi- which it would other wise get.
Far as I can tell, the original standard was "<5mm pi-, 5-10mm pi, 10-15mm pi+, 15-20mm pi++, 20mm+ pi++ (and not reduced by AP)"; there are no weapons in Basic that don't fit that rule (the only pi- weapons are .17 caliber shot, 4.6mm PDW, 4mm gauss, and the dart rifle).
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Old 11-20-2016, 07:08 AM   #24
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Default Re: What Is This Bullet For?

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Originally Posted by Anthony View Post
Far as I can tell, the original standard was "<5mm pi-, 5-10mm pi, 10-15mm pi+, 15-20mm pi++, 20mm+ pi++ (and not reduced by AP)"; there are no weapons in Basic that don't fit that rule (the only pi- weapons are .17 caliber shot, 4.6mm PDW, 4mm gauss, and the dart rifle).
I think it's referring more to the High tech rules:



4mm to 7.99mm (.16 to .31 caliber): At low velocities (pistol
cartridges or black-powder weapons), damage type is
small piercing (pi-); this models the behavior of rounds like
the .32 ACP (which fires a 7.95mm bullet), .25 ACP, and .22
LR. For bullets of this caliber fired from high-velocity
weapons (such as most centerfire rifles), damage type is piercing
(pi).



High Tech pg 163


Which was further elaborated on in Tactical shooting with regards the velocity point (TSpg61 "My Carbine Sucks/Rocks")
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Old 11-20-2016, 11:21 AM   #25
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Default Re: What Is This Bullet For?

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Originally Posted by Tomsdad View Post
Which IIRC is the justification for GURPS giving the 5.56 past a certain velocity Pi rather than Pi- which it would other wise get.
Yeah, the M855A1 is pretty frightening, actually. It has better penetration than M80 7.62mm ball, but tumbles 90-degrees between 1 and 3 inches of penetration and then fragments almost as well as the old 55-grain M193. Well, in ballistic gelatin, at least. And this is out of a 14.5-inch barrel, in contrast to the M193's 20-inch barrel. Which is pretty remarkable. Since it was fielded complaints about the 5.56mm lacking stopping power have more or less ceased- at least from the guys actually using it, as opposed to the chairborne commando brigade, who continue to promulgate rank idiocy, as always. This addresses much of it.

But it is important to note that 5.56mm is somewhat of an anomaly. It was more or less a fluke that the M193 worked as well as it did, and then the M855A1 was designed to do what it does. (Even though officially the only goal was better penetration, by happy "coincidence" the way that the designers went about it resulted in a very tail-heavy and tumbly round.) Other rounds of similar caliber (.22-ish) should not be assumed to work as well.

Last edited by acrosome; 11-20-2016 at 11:32 AM.
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Old 11-20-2016, 02:07 PM   #26
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Default Re: What Is This Bullet For?

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Originally Posted by acrosome View Post
Yeah, the M855A1 is pretty frightening, actually. It has better penetration than M80 7.62mm ball, but tumbles 90-degrees between 1 and 3 inches of penetration and then fragments almost as well as the old 55-grain M193. Well, in ballistic gelatin, at least. And this is out of a 14.5-inch barrel, in contrast to the M193's 20-inch barrel. Which is pretty remarkable. Since it was fielded complaints about the 5.56mm lacking stopping power have more or less ceased- at least from the guys actually using it, as opposed to the chairborne commando brigade, who continue to promulgate rank idiocy, as always. This addresses much of it.

Cheers for the link (and yeah bigger isn't always better)


Quote:
Originally Posted by acrosome View Post
But it is important to note that 5.56mm is somewhat of an anomaly. It was more or less a fluke that the M193 worked as well as it did, and then the M855A1 was designed to do what it does. (Even though officially the only goal was better penetration, by happy "coincidence" the way that the designers went about it resulted in a very tail-heavy and tumbly round.) Other rounds of similar caliber (.22-ish) should not be assumed to work as well.
I don't know if you familiar with it but Douglas Cole's Blog has a series of articles called the Reloading press , that goes into some details on some round and in some cases includes a stat line for when the rounds out of different barrel lengths would drop from Pi to Pi-.

Anyway cheers

TD
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Old 11-20-2016, 03:29 PM   #27
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Default Re: What Is This Bullet For?

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Originally Posted by acrosome View Post
Yeah, the M855A1 is pretty frightening, actually. It has better penetration than M80 7.62mm ball, but tumbles 90-degrees between 1 and 3 inches of penetration and then fragments almost as well as the old 55-grain M193. Well, in ballistic gelatin, at least. And this is out of a 14.5-inch barrel, in contrast to the M193's 20-inch barrel. Which is pretty remarkable. Since it was fielded complaints about the 5.56mm lacking stopping power have more or less ceased- at least from the guys actually using it, as opposed to the chairborne commando brigade, who continue to promulgate rank idiocy, as always. This addresses much of it.
What this amounts to is that a late TL8 round out performs a late TL6 one. I am certain a redesign of 7.62mm rounds could improve them dramatically, but first you'd have to figure out what their tactical purpose is.
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Old 11-20-2016, 04:00 PM   #28
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Default Re: What Is This Bullet For?

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What this amounts to is that a late TL8 round out performs a late TL6 one. I am certain a redesign of 7.62mm rounds could improve them dramatically, but first you'd have to figure out what their tactical purpose is.
Well, not only that but the TL8 round may be demonstrating virtues that neither HT nor UT really addresses as possible...
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Old 11-21-2016, 05:26 AM   #29
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Default Re: What Is This Bullet For?

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Originally Posted by Purple Haze View Post
What this amounts to is that a late TL8 round out performs a late TL6 one. I am certain a redesign of 7.62mm rounds could improve them dramatically, but first you'd have to figure out what their tactical purpose is.
The M80A1 is that redesign. You could say it's a late TL8 round as well.
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