That is why I asked for facts, any proof, to say a 115gr bullet cannot penetrate good enough to reach a heart. I simply do not believe it.
The question is not whether it can but rather whether it can with all of those bones in the way on a regular basis. Also whether a Heavier round can do so with I higher percentage of success. Finally (as you mentioned ) whether or not the .9 Gr difference is substantial enough to be measurable with a degree of certainty when related to lethality.
Several coroner reports have been made about bullets being deflected by bone and hit less than lethal parts of the human anatomy. Brassfetcher did a good write-up on the human skeleton.
http://www.brassfetcher.com/9x19mm Luger/9x19mm Luger Bone Test.pdf Good read and some interesting views of the skeleton and it's coverage of the vitals. What this tells us is even a good shot may not be good enough and accuracy may be less effective than one may think supporting the multiple shot stop theory.
Just the natural shape of the skeleton is designed to protect vitals and still be able to allow free movement. IMO it does it very effectively. There are factors in overcoming this natural defense but still a debate as among the most common handgun calibers as to which does it best or whether one gives a better percentage of success without sacrificing recoil or capacity.
There is one factor that affects the ability of a given caliber to penetrate well that is Kinetic Energy or KE.
and the less mentioned Potential Energy or PE
http://en.wikipedia.org/wiki/Potential_energy.
Though PE is used or referred to more in the use of a bow and arrow for example, it still applies to guns due to the stored energy being measurable and trajectories relationship to bullet ballistics within the equation.
The higher the energy the higher the energy transfer into an object and the greater the chance at good penetration and overcoming barriers such as bone, but again no guarantee.
KE is based on a measurement of Mass and velocity. The higher the velocity the higher the KE and the heavier the Mass the higher the resistance to an objects affect on reducing its kinetic energy thereby increasing penetration. Within a given round there are limits and balances must be made to effectively bring these to things together to get the best result. If neither were limited it would be easier to increase velocity to improve the chances of penetration through barriers both natural and unnatural though he recoil would increase as well. However they are limited by design.
But what has been found through science and testing over time is that mass makes up for a limited velocity and does so very well. Mass can penetrate more or fly further as the resistance to energy loss increased substantially by weight alone extending the ability of the cartridge to pack a more damaging punch and plow through those barriers with a higher degree of success.
Then it is said the 124gr bullets are more than adequate. How can this little difference in bullet weight ( this is the weight of a .177 airgun pellet! ) make such a big difference?
Some of what I covered can help to understand the increase in penetration. Doesn't mean the 124gr is the above and beyond better weight for a 9mm but it is better at penetrating. To what degree of efficiency is another question that is hard to answer. There is not really a proven percentage of lethality that says the 9gr increase in weight will effectively increase it's ability to overcome barriers and KE loss enough to make a substantial difference.
There are some tools that may help to give you a better idea of the differences but the best way to get some easy visuals it is through some of the ballistic test. Videos and charts are all over the web including
www.brassfetcher.com and YouTube.
Here's a good source on Mass effect on KE:
http://www.rsd17.org/TeacherWebPage/HighSchool/HFerrer/CH15MassVsKELabANSWERS.pdf
All of that and the discussion of HP ammo and how it effects the outcome. Penetration differences due to expansion, lack of expansion due to clogging, energy loss from barriers, KE depletion due to lack of weight, Over-penetration due to clogging (essentially becoming a ballistic equal to a FMJ).
In the end there are variables and more variables that cloud the small weight difference between the 115 and 124 in a 9mm. Spread it out a little more and there is more data with more discernible results. This Ballistics Gelatin test is interesting enough to mention:
http://www.ar15.com/ammo/project/Misc_Images/DocGKR/Handgun_gel_comparison.jpg
As weight, caliber and velocity change you can see the differences on the Ballistic Gelatin. However how does that relate to a real world and does it reflect the human body? Not as much as one would think. Center mass shots are located in the most protected part of the human body. There it is mostly bone where the penetration, expansion, trajectory and overall damage will most likely be drastically different than Ballistics Gelatin. The Exception that makes up the difference between most likely and most definitely would be if you squeezed a shot between the ribs.
In essence most JHP fail to expand through bone. Given that the Majority of the "center mass" is covered by bone penetration and caliber become your best friend.
Disregarding a failure to expand because your choice in JHP or even EFMJ is better and supposing they still expand the surface area of the round increases substantially. When that happens the larger area and heavier drag will deplete KE rapidly and dump it quickly into the body. With a lighter round the KE will deplete more quickly and penetration will be affected. How much depends again on more variables such as weight, velocity, and how quickly or slowly the round expands.
Even with all the information I have here there is room for critique. I am sure that something can be debated, calibrated or corrected. The weight debate is not much different than the caliber debate. Don't let it consume you as it has some.
:banghead:
