Question: "Muzzle Energy" vs. "Power Factor"

[Todd.K]

Unfortunately, energy calculation favors velocity, so you have to take it with a grain of salt - the 7.62x25 (Tokarev) cranks out 500+ ft/lbs of energy while delivering sub-optimal terminal performance.

Your own "unfortunate" reality completely undercuts the premise that energy numbers are useful.

That is why we are even having this debate. Because energy numbers don't reflect what we see in actual terminal performance, or what we want to see.

Power factor was made up so the mighty 45 APC single stack could compete against the wimpy but double stack 9mm.

Taylor made up the weighted KO formula to try to match up to hunting results with the single expanding bullet design of the time (and the lore of some calibers).

I still say there is no good reason to look at energy numbers when we can simply compare gel results of 9mm, .380, and 7.62x25 to make an informed decision.

[WillBrink]

Your own "unfortunate" reality completely undercuts the premise that energy numbers are useful.

That is why we are even having this debate. Because energy numbers don't reflect what we see in actual terminal performance, or what we want to see.

Power factor was made up so the mighty 45 APC single stack could compete against the wimpy but double stack 9mm.

Taylor made up the weighted KO formula to try to match up to hunting results with the single expanding bullet design of the time (and the lore of some calibers).

I still say there is no good reason to look at energy numbers when we can simply compare gel results of 9mm, .380, and 7.62x25 to make an informed decision.

Where as modern 9mm JHPs perform consistently well, .380 does not (at least last time I checked) and I never looked at 7.62x25 mm or considered it myself.

[Ron3]

I want to believe because it means my bullet choices matter more and I have more control. And i forget sometimes that it hardly matters.

A agree that we can largely not worry about theories when we have scales, chronograph's, and testing mediums of all kinds to see what really happens.

I've been thinking for awhile that the common thought that bullet design / cartridge power (within a certain realm) has more to do with "stopping power" than "killing power" is wrong. People often say, "sure, that bullet will kill, too, but this one is more likely to stop them quickly."

I believe the truth is bullets that do "better" in our test mediums aren't any more likely to "stop" but are probably better at killing. (Sooner or later)

I dont think the common service calibers are any better at "stopping" than weaker calibers. But they are better at keeping up that performance at greater distances and through barriers (For better or worse) and at killing the person shot. (For better or worse)

My criteria now is only to use HP's for the purpose of preventing over penetration as long as testing shows that bullet will normally both parachute and penetrate "enough".

"Stopping the attack quickly" only comes from nervous system damage and luck / chance / fortitude of the person shot.

More rounds on target quickly with enough penetration is the way. (After awareness, avoidance, tactics, etc)

[Ron3]

Unfortunately, energy calculation favors velocity, so you have to take it with a grain of salt - the 7.62x25 (Tokarev) cranks out 500+ ft/lbs of energy while delivering sub-optimal terminal performance.

Andy

Well, pretty good performance for a soldier at war in an urban area fired from a sub-machine gun but yes, if we're talking about handgun use in the US and fmj you're right. 😁

[Ron3]

Well, pretty good performance for a soldier at war in an urban area fired from a sub-machine gun but yes, if we're talking about handgun use in the US and fmj you're right. 😁

Since were on that...Hornady may as well make a 7.62x25 Critical Defense load. They have just about every other caliber and I think they'd make money on it. Low flash powder, low recoil load, small / pointed meplat for the Tok's. Betcha they do it.

[MegademiC]

I want to believe because it means my bullet choices matter more and I have more control. And i forget sometimes that it hardly matters.

A agree that we can largely not worry about theories when we have scales, chronograph's, and testing mediums of all kinds to see what really happens.

I've been thinking for awhile that the common thought that bullet design / cartridge power (within a certain realm) has more to do with "stopping power" than "killing power" is wrong. People often say, "sure, that bullet will kill, too, but this one is more likely to stop them quickly."

I believe the truth is bullets that do "better" in our test mediums aren't any more likely to "stop" but are probably better at killing. (Sooner or later)

I dont think the common service calibers are any better at "stopping" than weaker calibers. But they are better at keeping up that performance at greater distances and through barriers (For better or worse) and at killing the person shot. (For better or worse)

My criteria now is only to use HP's for the purpose of preventing over penetration as long as testing shows that bullet will normally both parachute and penetrate "enough".

"Stopping the attack quickly" only comes from nervous system damage and luck / chance / fortitude of the person shot.

More rounds on target quickly with enough penetration is the way. (After awareness, avoidance, tactics, etc)

Rounds that expand and penetrate deep enough to reach vitals is the most situations will result in the quickest incapacitation.

Unless a switch (CNS) is hit, you have to have blood pressure drop(ignoring psycological stops/drops). Expanding rounds through the heart, lungs, liver, or major arteries produce much quicker pressure drop than fmjs.

Bonded rounds (and hst) hold together through barriers (including extremities) allowing better penetration.

Expansion is key, because it tears tissue, as opposed to tissue stretching around the round (how many bow hunters use field points? How far will a heart shot deer run if a field point is used?)

Looking at energy, all service pistol rounds cause insignificant temp cavity damage.
The best rounds have to have enough energy to expand reliably and penetrate enough to reach vitals reliably. All normal rounds have enough energy to achieve this, and the limiting factor is the bullet design (see above). With a given energy, you have ‘x’ expansion and ‘y’ penetration. You can increase one, but the other will decrease with a given energy. Mass is another variable that will influence this. As weight goes down, so will penetration, due to the calculations of momentum.

Energy, or even momentum, in and if itself, when discussing service pistol calibers, is useless.
Any measure is useless except for the quantified results.

Gel testing (calibrated ordinance gel) has show the best way to measure load performance with a statistical correlation to real world results.

[LimeSpoon]

Duncan MacPherson's book lists different crush diameter coefficients for different shapes of bullets, but I think this may be largely speculatory, as examination of entrance wounds seems to show that diameter scales pretty closely with bullet diameter.

Flatter meplats and sharper edges do likely make a difference as the bullet slows down near the end of its track, and then a round projectile is more likely to push structures aside rather than cut or crush them. This could certainly be the case for relatively slow moving arrows. Earlier on though I would guess that most bullets incapable of temporary cavitation damage will crush a path about their size.

The main benefit to expansion it seems is the increase in frontal area, which, when viewed from a relative percentage standpoint, can be quite large.

So far as lethality is concerned...I would guess that increases in lethality would scale pretty well with increase in incapacitation ability in the short term. In the long term, however - that is to say, in regards to bullets that are not quickly fatal - there may be less difference than expected between a bullet that does more damage and a bullet that does less damage. The body has a number of compensatory mechanisms for adjusting to localized (and systemic) blood loss that can be quite effective, given time to work.

[Ron3]

Rounds that expand and penetrate deep enough to reach vitals is the most situations will result in the quickest incapacitation.

Unless a switch (CNS) is hit, you have to have blood pressure drop(ignoring psycological stops/drops). Expanding rounds through the heart, lungs, liver, or major arteries produce much quicker pressure drop than fmjs...

...Gel testing (calibrated ordinance gel) has show the best way to measure load performance with a statistical correlation to real world results.

When it comes to non-service scenarios I don't think the blood pressure loss caused stops come in to play often if the nervous system or psychological stop doesnt happen. It still takes several seconds during which the BG can fight if he wants. Even the deer often run after complete penetration with hunting tipped arrows.

As for the gel testing, its very helpful of course, but i dont think there is enough information to say there is a "statistical correlation with real world results". (For quick stops)

I guess my point is (individual) .32, .380, and .38 bullets are closer in performance (quick stops) to a service caliber jhp than we often think and the service caliber jhp's aren't much, if any more effective (at quickly stopping) than a lead ball from a .44 / .50 lead ball or .45 colt LFN.

But the service calibers are better at penetrating barriers, over penetrating (fmj or failed jhp's) people, performing at longer distances, and killing / killing more quickly.

[LimeSpoon]

When it comes to non-service scenarios I don't think the blood pressure loss caused stops come in to play often if the nervous system or psychological stop doesnt happen. It still takes several seconds during which the BG can fight if he wants. Even the deer often run after complete penetration with hunting tipped arrows.

Consider that it only takes a minor loss of blood pressure via orthostatic hypotension (i.e. standing up and getting dizzy) to immediately induce effects that would be highly detrimental in the context of a gunfight. While the body can tolerate surprisingly large amounts of blood loss over longer period of time, it appears to be far less adept at handling very rapidly inflicted trauma.

Further note that CNS shots comprise a minority of hits, and it's estimated only about half of incapacitations are psychological - something must account for the remainder.

Comparisons between deer and people are not always helpful; deer are more durable in some ways, more fragile in others. But if we are going to foray into effectiveness on quadrupeds, it might be noted that there were occasions during the Thompson-LaGarde tests where cows weighing much more than humans collapsed immediately after being shot multiple times in rapid succession - and only when shot multiple times in rapid succession. Autopsies displayed a lack of CNS damage.

[Todd.K]

As for the gel testing, its very helpful of course, but i dont think there is enough information to say there is a "statistical correlation with real world results". (For quick stops)

"Quick stops" are too variable to try to model or quantify. So I choose a load that performs reliably for the worst case. A service caliber and HST, GoldDot, ect, if possible. If you must go smaller pick penetration rather than expanding.

As far as actual damage in a shooting vs gel, DocGKR told me is is well studied in OIS shootings.