.40 Caliber Pressure Wave Effects

[Michael Courtney]

Could it be the temporary cavity impacting the spine and knocking it unconcious? On a deer a broadside shot might let this happen fairly easily even with a handgun. On a human its unlikely because of all that stands between spine and chest, and the human is likely to be facing you.

We don't think so, because in our handgun studies we carefully control shot placement very close to the horizontal midline. The TC only extends 2-3" from the wound channel, so that still leaves a significant gap between the highest point of the TC and the spine.

In observations with rifle bullets, we have also observed that there is a greater probability if immediate incapacitation in deer if the bullet hits 3" or so below the horizontal midline than if the bullet hits at the midline. This observation definitely suggests a pressure wave effect rather than the TC impacting the spine for two reasons:
1. This lower shot placement is closer to the aorta and more likely to transmit a large pressure wave to the brain.
2. Focussing effects in the ellipsoidal chest cavity produce a greater pressure wave at the spine with a hit lower in the chest than with a hit at the midline.

Michael Courtney

 

[lbmii]

The first thing we must do is to closely estimate the velocity that the 40 cal bullet was traveling when it hit the deer.

How sure are you of the distance?

Please chrono the round at that distance right away.

It is possible that the velocity was higher. But we need a test done to confirm.

I generally will go with a higher velocity bullet when choosing between two rounds of the same caliber and of about the same momentum. My carry round for my Glock 35 with a 5.3 inch barrel is the 155 grain gold-dot that I chronoed at 1245 fps.

But the first thing to do for this threads' discussion is to confirm the velocity of that 135 grain bullet. Please test for the velocity right away.

This is an excellent thread.

 

[Michael Courtney]

The first thing we must do is to closely estimate the velocity that the 40 cal bullet was traveling when it hit the deer.

How sure are you of the distance?

Please chrono the round at that distance right away.

It is possible that the velocity was higher. But we need a test done to confirm.

I generally will go with a higher velocity bullet when choosing between two rounds of the same caliber and of about the same momentum. My carry round for my Glock 35 with a 5.3 inch barrel is the 155 grain gold-dot that I chronoed at 1245 fps.

But the first thing to do for this threads' discussion is to confirm the velocity of that 135 grain bullet. Please test for the velocity right away.

This is an excellent thread.

We are in possession of the muzzleloading rifle used, as well as the identical lot of powder, bullet, sabot, and everything necessary to duplicate the load precisely. The location of the shooter was a permanent stand. The location of the deer was a pile of corn directly in front of a stack of firewood serving as a backstop. We will be able to measure the distance very accurately.

So, while the intitially reported distance is an estimate, we do intend to measure this exactly, as well as chronographing the load and measuring the time of flight to confirm the loss of velocity in flight. I prefer not to chronograph bullets at these ranges because uncertain accuracy can get expensive if the chronograph is hit. Using a time of flight measurement is standard in the industry for confirming ballistic coefficient.

We have permission to visit the privately owned site again soon to confirm everything necessary to be as certain as possible of the impact velocity.

Michael Courtney

 

[Michael Courtney]

The first thing we must do is to closely estimate the velocity that the 40 cal bullet was traveling when it hit the deer.

How sure are you of the distance?

Please chrono the round at that distance right away.

It is possible that the velocity was higher. But we need a test done to confirm.

I generally will go with a higher velocity bullet when choosing between two rounds of the same caliber and of about the same momentum. My carry round for my Glock 35 with a 5.3 inch barrel is the 155 grain gold-dot that I chronoed at 1245 fps.

But the first thing to do for this threads' discussion is to confirm the velocity of that 135 grain bullet. Please test for the velocity right away.

This is an excellent thread.

We were able to do some measurements at the original shooting site today. Our original estimate of the distance from gun to deer was 65 yards. The actual measured distance is 72 yards. Our original estimate of the impact velocity was 1350 FPS. Using a time of flight measurement of the bullet from the actual deer stand to the point where the deer was standing 72 yards away, our new estimate of the impact velocity is 1250 FPS. Some uncertainty remains (the impact velocity could have been slightly higher) since our measurements this morning were made at an ambient temperature of 18 degrees F, and the original shooting took place at an ambient temperature of 33 degrees F.

However, it is extremely unlikely that a temperature difference of 15 degrees F could cause an impact velocity increase over 100 ft/s. If we decide to include this result in a publication, we will arrange to perform our time of flight and chronograph measurements at closer to 33 degrees F.

Michael Courtney

 

[lbmii]

Interesting, by any chance did you get photos of the deer?

I now keep a disposable camera in my glove box just for those Kodak moments.

Did the bullet impact a rib or did it go between the ribs?

I once worked at a deer check in station and the wounds were somewhat greater when the bullet had struck a bone.

 

[Michael Courtney]

Interesting, by any chance did you get photos of the deer?

I now keep a disposable camera in my glove box just for those Kodak moments.

Yes, we've got photographs. They were posted to a Glocktalk thread of similar title. I am willing to post them here, but was concerned that the moderators may not approve.

Did the bullet impact a rib or did it go between the ribs?

We don't believe it is possible to determine with objective certainty whether or not a bullet has impacted a rib when entering a ruminant animal from the side. Post-mortem examination can only infer whether or not ribs are fractured and what kind(s) of fractures were sustained, but we do not believe that every bullet that hits a rib results in clear evidence of a fracture, nor do we believe that every fracture gives evidence of a rib hit.

Low velocity projectiles can sometimes glance off of a rib without creating a fracture. Bullets which create very large pressure waves can sometimes break ribs without impacting them directly. (We've observed cases with as many as three adjacent broken ribs with high pressure wave bullets, the bullet did not hit all three.)

In this case, the ribs were not fractured by the bullet on entrance. Given the bullet velocity, this probably means the bullet did not hit the ribs, but we would not conclude that with certainty.

I once worked at a deer check in station and the wounds were somewhat greater when the bullet had struck a bone.

This effect is more pronounced when the bullet hits hip, leg, or spine bones than with ribs. There are actually different schools of thought on whether hitting a rib is beneficial or detrimental to bullet performance. On the one hand, I think whether or not hitting a rib is beneficial depends on the bullet design and the velocity. On the other hand, I don't think the question can be reliably answered, because of the afore-mentioned difficulties in being certain whether or not a bullet hit a rib.

The Strasbourg Goat Tests attempted to address this question, but I think they lacked a truly objective criteria for determining whether or not a rib had been hit. I regard the Strasbourg Tests as an accurate measurement of incapacitation times, because their criteria for incapacitation was objective. However, I do not regard the Strasbourg Tests as a valid indicator of the benefit/detriment of hitting a rib, because they lacked an objective criteria for determining whether or not a rib had been hit.

Michael Courtney