More Powerful, 9mm or 40 caliber?

Let me end this argument now:

Explain how a 9x19mm can penetrate just as deeply as a .40 S&W with much more speed, much more momentum, much more energy with nearly identical expansion under nearly identical conditions.

(Some would say it's because of the bullet size, but remember, we are talking similar expansion, which renders that argument moot).

For example:

9x19mm Federal HST 147gr: 1004 fps @ 329 KE // 12.0" Pen, 0.85" Exp // Sectional Density = 0.166 // Momentum ~ 21.1 mv

.40 S&W Federal HST 165gr: 1156 fps @ 489 KE // 12.0" Pen, 0.87" Exp // Sectional Density = 0.147 // Momentum ~ 26.5 mv

Here we have a 9mm with much less momentum, much less energy, much less velocity, yet we have exactly the same penetration with nearly identical expansion.

How can you explain this?

And here is the "killing" blow:

.357 SIG Federal HST 125gr: 1412 fps @ 550 KE // 11.0" Pen, 0.83" Exp // Sectional Density = 0.142 // Momentum ~ 25.2 mv

Here we have a .357 SIG bullet which is nearly identical in size to the 9mm (0.355" to 0.356") traveling with much more momentum than the 9mm, but actually exhibits less penetration with nearly identical expansion.
 
AZHawk, the body is around 70% water.

Tissue will have drag and resistance characteristics much more similar to that of water than, say, that of wood or metal.

Water and other fluids (and gases) resist motion into and through them at a ratio that goes up with velocity, squared. So the initial resistance to a higher velocity round is MUCH greater than the initial resistance against a lower velocity round.

Also, depending on bullet construction, the higher velocity round will often be more likely to fragment.
 
And......?

Use that to explain this:

9x19mm Federal HST 124gr versus 9x19mm Federal HST 124gr +P versus .357 SIG Federal HST 125gr

124gr HST: 1158 fps @ 369 KE // 11.0" Pen, 0.88" Exp // Sectional Density = 0.140 // Momentum ~ 20.5 mv

124gr +P HST: 1260 fps @ 437 KE // 10.0" Pen, 0.87" Exp // Sectional Density = 0.140 // Momentum ~ 22.2 mv

125gr HST: 1412 fps @ 553 KE // 11.0" Pen, 0.83 Exp // Sectional Density = 0.142 // Momentum ~ 25.2 mv

P.S. The human body is actually about 60% water.
 
AZ Hawk
"How about this:

Federal HST Ballistics in bare gelatin.

155gr HST - 1198 fps @ 493 KE // 10.5" Penetration, 0.96" Expansion // Sectional Density = 0.138

165gr HST - 1156 fps @ 489 KE // 12.0" Penetration, 0.87" Expansion // Sectional Density = 0.147

180gr HST - 1041 fps @ 433 KE // 12.0" Penetration, 0.96" Expansion // Sectional Density = 0.161

155gr HST has more momentum, more kinetic energy, the same expansion but has less overall penetration than the 180gr HST."

The HST 155 and 180 have the same momentum. The sectional density of the expanded bullets is:

155 gr .024
180 gr .028

So the same momentum with a better SD for the 180 gr gives more penetration.
 
AZHawk, your post supports my point. Equivalent sectional density, and the faster round (which would generate more initial reaction and drag) decelerated faster, and penetrated less.

Rounds which achieve momentum through mass out penetrate rounds that achieve momentum through velocity.

We're both arguing the same effect, but sectional density is only part of the answer, as your own post (.357SIG vs 9mm) demonstrated.
 
Note: velocity will do better against a thin barrier with less fluid content, such as a kevlar vest or the sheet steel of a car door.
 
Note 2: in your earlier example, the 125gr HST has significantly more velocity, so even though it has higher initial resistance, it still has extra velocity with which to absorb the higher acceleration. Note, though, that it's velocity edge did not translate into a direct percentage of penetration gain (edit: as compared to the 124gr +P; it only penetrated equally to the slowest round.) Velocity provides diminishing returns with regard to penetration of a largely fluid medium.
 
AZ Hawk

"Let me end this argument now:

Explain how a 9x19mm can penetrate just as deeply as a .40 S&W with much more speed, much more momentum, much more energy with nearly identical expansion under nearly identical conditions.

(Some would say it's because of the bullet size, but remember, we are talking similar expansion, which renders that argument moot).

For example:

9x19mm Federal HST 147gr: 1004 fps @ 329 KE // 12.0" Pen, 0.85" Exp // Sectional Density = 0.166 // Momentum ~ 21.1 mv

.40 S&W Federal HST 165gr: 1156 fps @ 489 KE // 12.0" Pen, 0.87" Exp // Sectional Density = 0.147 // Momentum ~ 26.5 mv

Here we have a 9mm with much less momentum, much less energy, much less velocity, yet we have exactly the same penetration with nearly identical expansion.

How can you explain this?

The most obvious reason is simple. You don't know how fast the bullets expand. Given a similar HP form, the faster bullet will expand faster. If the .40 is fully expanded in 1" and the 9mm takes 3" to expand it would explain the difference. Since Federal designs the bullets to meet the FBI minimum, this is a very likely scenario.

And here is the "killing" blow:

.357 SIG Federal HST 125gr: 1412 fps @ 550 KE // 11.0" Pen, 0.83" Exp // Sectional Density = 0.142 // Momentum ~ 25.2 mv

Here we have a .357 SIG bullet which is nearly identical in size to the 9mm (0.355" to 0.356") traveling with much more momentum than the 9mm, but actually exhibits less penetration with nearly identical expansion. "

Again, the faster bullet will expand sooner therefore reduced penetration is probable. If you could see a side view of the 125, you'd probably see that the petals over expanded (larger than .83) and then were pushed back to a smaller diameter. It's not the unexpanded SD that matters. Even the final expanded diameter SD does not tell the entire story. You really need an average SD for the entire length of penetration.
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AZ Hawk

"And......?

Use that to explain this:

9x19mm Federal HST 124gr versus 9x19mm Federal HST 124gr +P versus .357 SIG Federal HST 125gr

124gr HST: 1158 fps @ 369 KE // 11.0" Pen, 0.88" Exp // Sectional Density = 0.140 // Momentum ~ 20.5 mv

124gr +P HST: 1260 fps @ 437 KE // 10.0" Pen, 0.87" Exp // Sectional Density = 0.140 // Momentum ~ 22.2 mv

125gr HST: 1412 fps @ 553 KE // 11.0" Pen, 0.83 Exp // Sectional Density = 0.142 // Momentum ~ 25.2 mv"

Again, it's fairly well know that driving the same bullet faster doesn't always get more penetration. It depends on the velocity the bullet is designed to operate at. The faster bullet will expand faster and often to a larger diameter before the petals are pushed back to a smaller diameter.
 
I always say if you want to guarantee a win in a firefight, you bring either a rifle or shotgun.

Sidearms are an absolute last resort regardless of caliber so just choose a handgun you are comfortable/capable with and you will be served well.

Me personally, I carry a 9mm 90% of the time and either a 22lr or 45acp the rest of the time always contingent on the occasion/attire.

Yet make no mistake, in a SHTF scenario, out comes my Saiga 12 and 1187P with a backup pistol.

-Cheers
 
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