I don't necessarily believe this, but bear with me a moment.  It is true that longer heavier bullets have better fragmentation at lower velocities due to their their long legnth.  They also appear to have more catastrophic wound profiles, but there may be a problem.  Every lunk head on ar15.com knows that fragmentation is the primary wounding device of M193 and M855, and that this fragmentation works so well (at least in theory) b/c it takes advantage of the temporary wound channel.  By this I mean that when the bullet is entering it causes a temporary wound profile many times the size of the projectile diameter as a result from the extreme velocity of rifle projectiles.  Sometimes the velocity from the projcetile may be so high, that this shock wave causes significant tearing even of rather elastic body tissues, so that when the tissue collapses the final resulting wound profile is significantly larger than the projectile diameter.  With enough velocity (and weight), this may happen even with non fragmenting projectiles, however the M193, for ex,capitalizes on this moment of wound profile expansion by showering the walls of the stretched cavity with fragments of hot lead that cause a bunch of tearing thus makes the "temporary" wound channel rather permanent and messy.  
   Now we all understand the above, my ?, that I hope gets addressed by many, especially those testing the newer heavier grain bullets is: Is it possible that when velocity is reduced, even though fracturing occurs well at much lower velocities with these longer projectiles, that there is a significant reduction of the force of the strecthing incurred in the temporary wound channel reduces the effectiveness of the fragmenting.  Let me say it again, without hyper velocity stretching the wound profile violently enough, will the fragmenting merely create a series of insignificant wound channels radiating of the main wound channel, OR will the fragments be able to create a more singular large jagged wound cavity???  

Yes, I have seen the pictures of the 75, 77, and 100gn projectiles in Ballistic gelatin, but it is not clear to me whether the little fragment channels are the type that let a good amount of blood into the main channel (and then out of the body), or if they are so small that the hydrolic pressure in the surrounding tissues simply collapses the little channel and prevents blood flow.  Consider the head on cross sections of blocks of gelatin shot with these heavier loads compared to say m193 looking at the relative size of the main channel to the other channels.  

Thanks  

There's a couple of thing which you may not have considered. First of these is that the difference between the "hyper" velocity M193/M855 and the "slower" heavy bullets isn't all that great. If you look at the temporary cavity produced by the AK47 (2450fps), you'd still find a substantial temporary cavity.

The second thing is that the tearing of the temporary cavity, while an added "bonus", is not necessarily the MAIN wounding mechanism. Rather, it's the large permanent cavity produced by the fragments themselves.

As I've mentioned on another thread, I've got a bunch of Dr. Fackler's articles coming on line which should hopefully give you enough answers.

It actually has more to do with their lower structural strength, though this is often a function of length.


I don't think so.  No.  Temporary cavity doesn't increase all that much with large increases in velocity.  It also does not take much temporary cavity to open the door for additional tissue damage due to fragments.  It is more about how stretched the local tissue is when the fragments hit.  Try this: poke a hole in a deflated balloon with a pin.  Not very exciting.  Now stretch the balloon (don't inflate) and poke a hole in it.  See the ripping?  Same effect.


Having worked with gel cross sections of rounds ranging from 55gr FMJ to 100gr OTM I can tell you that rounds like the 68, 69, 75, 77 and 100 grain FMJ/OTMs are leaving much more devastating wounds than M193 or M855.  Cavities are larger.  There are more of them.  They stay wide deeper into the gel.

The reverse is actually typically true of the statement you make above.  Higher velocities mean that fragmentation is more violent and therefore the main cavity divides into several smaller cavities shallower in gel.  (Same reason hollow points in .223 fragment too fast and don't wound as well).  As a general rule lower velocities do not subject fragments to as much shearing force and therefore the fragments stay larger longer, retain more penetrating energy and therefore go deeper and leave wider cavities in their wake.  Combine that with more mass to begin with (heavier bullets) and you get the idea.

[Alright, I admit it, I called my sister for help]

I agree with you and your sister (and Forest and Zhukov too)! The next time you talk to her tell her all the folks here at ARF.com sorely miss all of her posts and to hurry back soon!

-Charging Handle

Hey there Doc, nice to see you over here!

-Charging Handle