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Old 02-21-2010, 22:17   #536
glock20c10mm
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Originally Posted by long shot View Post
Craig, no harm done.

Quote:
Only Dr. Roberts can answer why he considers the work of Dr. Courtney to be complete 'BS' as you stated. Personally, I would look at it this way: if my load already performed to protocol AND I could also potentially obtain another wounding mechanism via BPW, so much the better. While I may not switch to say a faster load (if necessary) soley to potentially achieve BPW ... I would have no problem at all if a certain load I was comfortable with and carried, afforded me the potential to achieve it.
I don't know how much of this thread you've followed, but I think a couple of posts bear repeating since it is such a long thread and good information can get lost in the depth of it.

Therefore I'm copy/pasting parts of post numbers: 376, 379, and 381. The main reason is to show you that more velocity alone doesn't neccessarily equate to more BPW. You may not care, but in case you're interested among possible others, the info is as follows.

The following are the current estimated probabilities of BPW playing a role for humans taking an unobstructed hit to the chest for given pressure wave magantudes:

BPW Probablility
500psi = 15%
700psi = 50%
1000psi = 75%
1300psi = 90%

The probability approaches 100% as BPW continues to increase, but will never really reach 100%. The accuracy in the prediction is roughly 10%.


The equation for JHP handgun bullets with 100% mass retention is -
p = (5*E)/(pi*d)

p is the peak pressure wave magnatude on the surphase of a 1" diameter cylinder centered on the wound channel (in psi). E is the impact energy (in ft-lbs) and d is the penetration depth (in feet).

If a JHP bullet fragments then generally whatever % the bullet fragments is the same % you need to add to the PBPW originally figured for nonfragmentation.

For FMJ handgun bullets the equation changes to a reasonable approximation of -
p = (3*E)/(pi*d)

For FMJ rifle bullets there is much more variation because some tumble deep and some tumble at shallow depths and some fragment. The retarding force profile (the more retarding force the greater the PBPW) is dominated by the depth at which a FMJ rifle bullet tumbles.

An FMJ rifle bullet which does not fragment and tumbles late in the penetration (10" or more) will have a peak pressure wave comparable to the formula for FMJ pistol bullets.

An FMJ rifle bullet which does not fragment and tumbles early (first 4") will have a peak pressure wave comparable to the formula for JHP handgun bullets.

If kinetic energy and penetration depth are equal, bullets that fragment create a larger pressure wave than bullets that retain 100% of their mass because the average penetration depth is shorter than the maximum penetration depth. Less penetration depth with equal kinetic energy = higher PBPW.

The following is why bullet fragmentation increases the level of peak ballistic pressure wave -

If kinetic energy and penetration depth are equal, bullets that fragment create a larger pressure wave than bullets that retain 100% of their mass. This is because the average penetration depth is shorter than the maximum penetration depth. Recall that the average force with no mass loss is given by [COC06c]

Fave = E/d,

where E is the kinetic energy and d is the maximum penetration depth.

If we consider the case of a bullet with some fraction, f, of mass lost to fragmentation, the fraction of retained mass is (1-f) and the average force is then given by

Fave = (1-f)E/d + f E/df,

where df is depth of the center of mass of the bullet fragments. In other words, df is the average penetration depth of the fragments. Most fragments do not penetrate as deeply as the maximum penetration depth d, so that the average fragment penetration depth df can be expressed as a fraction of the maximum penetration depth

df = d/k,

where k is greater than 1. Consequently, the average force becomes,

Fave = (1-f)E/d + f k E/d.

This can be rewritten as

Fave = [1 + f (k-1)]E/d.

So we see that the enhancement factor for the average force is [1 + f(k 1)], where f is the fraction of lost mass, and k describes the relative penetration depth of the mass lost by fragmentation. If the mass lost by fragmentation penetrates of the maximum penetration depth on average, k = 2, and the enhancement factor for the average force is (1+f). In other words, a 40% loss of mass increases the average force (and thus the pressure wave) by 40%.

If the mass lost by fragmentation penetrates ⅓ of the maximum penetration depth on average, k = 3, and the enhancement factor for the average force is (1+2f). In other words, a 40% loss of mass increases the average force (and thus the pressure wave) by 80%.

Consequently, bullets that fragment can create larger pressure waves than bullets that do not fragment but have the same kinetic energy and penetration depth. Most fragmenting bullets have an average fragment penetration depth of ⅓ to of their maximum penetration depth, so that the pressure wave enhancement factor is between (1+f) and (1+2f).

In other words, a bullet which loses 10% of its original mass has a BPW 10-20% larger than one which retains 100% of its original mass. Likewise , a bullet which loses 30% of its original mass to fragmentation has a BPW 30-60% larger than one which retains 100% of its original mass.


I have run the numbers for various common SD loads where I could get the pertinent apples to apples comparison data so we can see how different loads stack up against each other. The list is as follows -

The kinetic energy is listed after "KE", penetration depth is listed after "P" and is based on clothed gel for ALL rounds, expanded bullet diameter is listed after "E", wound volume is listed in cubic inches(ci) and is based on 12" penetration for ALL rounds unless a specific round couldn't manage 12" penetration, and in the last column in pounds per square inch(psi) is the peak ballistic pressure wave. Please note - for PBPW, for any round that fragmented to any extent, the PBPW is actually higher than what's shown. All PBPW numbers assume zero fragmentation. Very generally, for the PERCENTAGE a round fragments, that same percentage would be added to the PBPW in psi.

Most of the HST #s and Speer Gold Dot #s are based on averages from the ATK workshop results with various police departments. Those that aren't based on an average were tested only 1 time. Those workshop results can be viewed in their entirety here - http://www.le.atk.com/general/irl/woundballistics.aspx

Win 380auto T Series, 95gr, 1000fps, KE=211, P=7.95, E=.64, 2.6ci, 507psi

Speer 38special+P GD, 135gr, 860fps, KE=222, P=11.75, E=.59, 3.2ci, 361psi
Win 38spcl T Series+P, 130gr, 925fps, KE=247, P=12.00, E=.67, 4.2ci, 393psi

Win 9mm+P+ Ranger, 115gr, 1335fps, KE=455, P=8.50, E=.81, 4.4ci, 1023psi
DT 9mm+P Gold Dot, 115gr, 1415fps, KE=511, P=12.00, E=.70, 4.6ci, 813psi
DT 9mm+P Gold Dot, 124gr, 1310fps, KE=472, P=13.25, E=.70, 4.6ci, 684psi
Federal 9mm+P HST, 124gr, 1200fps, KE=396, P=12.50, E=.66, 4.1ci, 605psi
Federal 9mm HST,,,, 124gr, 1150fps, KE=364, P=13.90, E=.64, 3.9ci, 501psi
Win9mm+P T Series, 124gr, 1180fps, KE=383, P=13.90, E=.67, 4.2ci, 526psi
Win9mm +P Bonded, 124gr, 1180fps, KE=383, P=18.70, E=.54, 2.7ci, 392psi
Win9mm+P+TSeries, 127gr, 1250fps, KE=441, P=12.20, E=.68, 4.4ci, 691psi
DT 9mm+P Gold Dot, 147gr, 1125fps, KE=413, P=14.00, E=.66, 4.1ci, 563psi
Federal 9mm HST,,,, 147gr, 1000fps, KE=326, P=14.40, E=.66, 4.1ci, 433psi
Speer 9mm GD,,,,,,,, 147gr,, 990fps, KE=320, P=15.25, E=.58, 3.2ci, 401psi
Win 9mm T Series,,,, 147gr,, 990fps, KE=320, P=14.50, E=.66, 4.1ci, 422psi
Win 9mm Bonded,,,,, 147gr,, 995fps, KE=323, P=16.50, E=.59, 3.3ci, 374psi

DT 357SIG Gold Dot, 115gr, 1550fps, KE=613, P=12.12, E=.71, 4.8ci, 955psi
DT 357SIG Gold Dot, 125gr, 1450fps, KE=584, P=14.50, E=.66, 4.1ci, 770psi
Win357SIG T Series, 125gr, 1350fps, KE=506, P=12.10, E=.66, 4.1ci, 798psi
Win357SIG Bonded,, 125gr, 1350fps, KE=506, P=15.90, E=.57, 3.1ci, 608psi
DT 357SIG Gold Dot, 147gr, 1250fps, KE=510, P=14.75, E=.73, 5.0ci, 661psi

DT 357mag Gold Dot, 125gr, 1600fps, KE=710, P=12.75, E=.69, 4.5ci, 1063psi
Speer SB 357magGD, 125gr,,, 990fps, KE=294, P=14.50, E=.65, 4.0ci, 388psi
Win 357magSilvertip, 145gr, 1290fps,, KE=536, P=12.50, E=.59, 3.3ci, 819psi
DT 357mag Gold Dot, 158gr, 1400fps, KE=688, P=19.00, E=.56, 3.0ci, 692psi

DT 9X25 Gold Dot, 115gr, 1800fps, KE=827, P=10.00, E=.64, 3.2ci, 1579psi
DT 9X25 Gold Dot, 125gr, 1725fps, KE=826, P=15.00, E=.74, 5.2ci, 1051psi
DT 9X25 Gold Dot, 147gr, 1550fps, KE=784, P=17.50, E=.68, 4.4ci,, 856psi

DT 40S&W Nosler,,,, 135gr, 1375fps, KE=567, P=12.10, E=.72, 4.9ci, 894psi
DT 40S&W Gold Dot, 155gr, 1275fps, KE=559, P=13.00, E=.76, 5.4ci, 825psi
DT 40S&W Gold Dot, 165gr, 1200fps, KE=528, P=14.00, E=.70, 4.6ci, 721psi
Rem Golden Saber,,, 165gr, 1150fps, KE=485, P=14.00, E=.67, 4.2ci, 662psi
Federal 40S&W HST, 165gr, 1130fps, KE=468, P=14.00, E=.75, 5.3ci, 637psi
Win40S&W T Series, 165gr, 1140fps, KE=476, P=13.20, E=.70, 4.6ci, 690psi
Win 40S&W Bonded, 165gr, 1140fps, KE=476, P=19.00, E=.55, 2.9ci, 479psi
Speer 40S&W GD,,,, 180gr. 1025fps, KE=420, P=11.75, E=.72, 4.9ci, 683psi
DT 40S&W Gold Dot, 180gr, 1100fps, KE=484, P=14.75, E=.68, 4.4ci, 626psi
Federal 40S&W HST, 180gr, 1010fps, KE=408, P=13.40, E=.77, 5.6ci, 582psi
Rem JHP (not GS),,,, 180gr, 1015fps, KE=412, P=13.25, E=.69, 4.5ci, 594psi
Win40S&W T Series, 180gr,,, 990fps, KE=392, P=14.30, E=.70, 4.6ci, 524psi
Win 40S&W Bonded, 180gr,, 1070fps, KE=458, P=21.80, E=.51, 2.5ci, 402psi

DT 10mm Nosler,,,, 135gr, 1600fps, KE=767, P=11.00, E=.70, 4.2ci, 1332psi
DT 10mm Gold Dot, 155gr, 1475fps, KE=749, P=13.50, E=.88, 7.3ci, 1061psi
DT 10mm G. Saber, 165gr, 1425fps, KE=744, P=14.75, E=.82, 6.3ci, 964psi
DT 10mm Gold Dot, 165gr, 1400psi, KE=718, P=14.25, E=1.02, 9.8ci, 962psi
DT 10mm Gold Dot, 180gr, 1300fps, KE=675, P=15.25, E=.96, 8.7ci, 846psi
DT 10mm G. Saber, 180gr, 1330fps, KE=707, P=16.00, E=.85, 6.8ci, 844psi
DT 10mm Hor. XTP, 180gr, 1350fps, KE=728, P=17.25, E=.77, 5.6ci, 808psi
DT 10mm Hor. XTP, 200gr, 1250fps, KE=694, P=19.50, E=.72, 4.9ci, 680psi

Win 45GAP T Series, 230gr, 905fps, KE=418, P=12.70, E=.72, 4.9ci, 630psi

DT 45auto Gold Dot, 185gr, 1225fps, KE=616, P=12.75, E=.82, 6.3ci, 923psi
Rem45auto G Saber, 185gr, 1140fps, KE=534, P=14.25, E=.70, 4.6ci, 716psi
Win45auto Silvertip, 185gr, 1000fps, KE=411, P=13.25, E=.70, 4.6ci, 593psi
DT 45auto Gold Dot, 200gr, 1125fps, KE=562, P=14.25, E=.88, 7.3ci, 753psi
DT 45auto Gold Dot, 230gr, 1010fps, KE=521, P=15.25, E=.95, 8.5ci, 653psi
Federal45auto+P HST,230gr, 950fps, KE=461, P=14.60, E=.85, 6.8ci, 603psi
Federal 45auto HST, 230gr,, 890fps, KE=405, P=14.40, E=.86, 7.0ci, 537psi
Speer 45auto G Dot, 230gr,, 890fps, KE=405, P=13.50, E=.70, 4.6ci, 573psi
Rem45auto G Saber, 230gr,, 875fps, KE=391, P=14.00, E=.74, 5.2ci, 534psi
Win 45auto T Series, 230gr, 905fps, KE=418, P=12.70, E=.72, 4.9ci, 630psi
Win45auto+PTSeries, 230gr, 990fps, KE=500, P=15.20, E=.78, 5.7ci, 628psi
Win 45 auto Bonded, 230gr, 905fps, KE=418, P=15.80, E=.67, 4.2ci, 506psi


Bottom line, a number of different factors alone can increase or decrease the level of peak ballistic pressure wave. So if nothing else in the equation changes, the following by themselves will change the PBPW - penetration depth, velocity, kinetic energy, and bullet design/construction.

Here are some examples using the above data:

First lets take this load -
Federal 9mm+P HST, 124gr, 1200fps, KE=396, P=12.50, E=.66, 4.1ci, 605psi
We'll leave everything else the same but change the velocity to 1100fps. This change changes PBPW to 509psi.

Then this load -
Federal 40S&W HST, 180gr, 1010fps, KE=408, P=13.40, E=.77, 5.6ci, 582psi
We'll leave everything else the same but change the penetration depth to 12". This change changes PBPW to 650psi.

Those two examples should be enough to give you an idea of how not only can velocity change the PBPW, but how it and other factors alone can change it too.

I hope the above, if you cared to read through it, helps you understand more clearly where Dr. Courtney's theory is coming from.
Quote:
In any event, the jest of my posts was that the IWBA/FBI protocol has indeed been one of the primary driving forces behind today's best ammunition.



Good Shooting,
Craig
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