Thread: Knockdown power

As others have pointed out, knock down power in terms of the bullet’s kinetic energy literally knocking an animal over, is a myth. The reason an animal gets poleaxed is generally when the bullet has caused catastrophic damage to the brain, spinal column, or the autonomic plexus; it wasn’t dropped by straight out kinetic energy.

But in my mind kinetic energy is still critical for a quick kill. There’s been a bit of discussion in this thread about hydrostatic shock, temporary wound channels, and blood pressure spikes to the brain all causing immediate incapacitation, even though the bullet may not have directly hit and damaged the CNS. I’m no pathologist but this makes a lot of sense to me. If we compare a bow hunter making a clean double lung shot on a red hind at 50yd, to a rifle hunter also making a lung shot on a hind at 150yd, what is the likely outcome? In the archery scenario the arrow has arrived with minimal energy, maybe 100ftlb, but it has still inflicted massive damage to the lungs and associated blood vessels. Despite this the hind still runs 75yd until she expires from blood loss. And what of our mate with a 270 or 308 running some SSTs at a decent speed? Well the hind 150yd away has been completely flattened. The SST has arrived with over 2000ftlb of energy and caused massive damage to the lungs, and has also instantly incapacitated the hind. Was this caused by hydrostatic shock or some other mechanism? I have no idea but kinetic energy is a good thing!

Originally Posted by 7.62

If we compare a bow hunter making a clean double lung shot on a red hind at 50yd, to a rifle hunter also making a lung shot on a hind at 150yd, what is the likely outcome? In the archery scenario the arrow has arrived with minimal energy, maybe 100ftlb, but it has still inflicted massive damage to the lungs and associated blood vessels. Despite this the hind still runs 75yd until she expires from blood loss. And what of our mate with a 270 or 308 running some SSTs at a decent speed? Well the hind 150yd away has been completely flattened. The SST has arrived with over 2000ftlb of energy and caused massive damage to the lungs, and has also instantly incapacitated the hind. Was this caused by hydrostatic shock or some other mechanism? I have no idea but kinetic energy is a good thing!

Very much a function of where in the lungs the animal is shot though. It's a good example, but not a guaranteed outcome.

Bowhunters need to avoid the leg bones, so shoot for the "crease" or just behind, around rib #6-7 give or take. Oftentimes, this point of aim actually ends up a bit further back. The expert bowhunter wants a quartering angle so the broadhead runs diagonally forwards across the vitals, not perpendicular to the spine.

Rifle hunters often deliberately aim for the leg bones - the hilar shot for example is taught as "front line of the foreleg". Regardless, the point of impact is around rib #3-4. The lungs behind ribs 3-4 are sat right on top of and surround the aorta and autonomic plexus, where the pulmonary arteries enter the lungs (the hilar). A fragmenting bullet like the SST with 2000 ft/lb doesn't just make a hole in the lungs, it instantly depressurizes the entire body's blood supply and terminally scrambles the CNS. A good hilar shot destroys the pulmonary arteries, aorta and CNS. Bang, flop.

The rifle hunter who hits a deer around rib #7 has got a runner to deal with. When he catches up with it and guts it, he sees a dirty big hole through the rear pointy section of the lungs, and can't understand how the animal made it so far. This part of the lungs actually bleeds quite slowly.

A couple of weeks ago an acquaintance in Victoria shot a large sambar with his 9.3x64 Brenneke (285gr) from 60m. Long story about how hard the recovery was, the damn deer took off like a top fuel dragster, downhill, in thick timber. This fella makes a lot of noise about how tough sambar are, and hence the rifle - everything has to be bigger and better to take down these leviathans of the forest. But the bottom line is that he doesn't aim far enough forward, and hits them too far back. In the High Country, in winter, that's a real pain in the arse. With that amount of energy (almost 4000 ft/lb!) the animal should be poleaxed. There's only one reason why it is able to run away, even if only for 10-20 seconds - it can cover a lot of ground in that short time...

Originally Posted by 7.62

As others have pointed out, knock down power in terms of the bullet’s kinetic energy literally knocking an animal over, is a myth. The reason an animal gets poleaxed is generally when the bullet has caused catastrophic damage to the brain, spinal column, or the autonomic plexus; it wasn’t dropped by straight out kinetic energy.

But in my mind kinetic energy is still critical for a quick kill. There’s been a bit of discussion in this thread about hydrostatic shock, temporary wound channels, and blood pressure spikes to the brain all causing immediate incapacitation, even though the bullet may not have directly hit and damaged the CNS. I’m no pathologist but this makes a lot of sense to me. If we compare a bow hunter making a clean double lung shot on a red hind at 50yd, to a rifle hunter also making a lung shot on a hind at 150yd, what is the likely outcome? In the archery scenario the arrow has arrived with minimal energy, maybe 100ftlb, but it has still inflicted massive damage to the lungs and associated blood vessels. Despite this the hind still runs 75yd until she expires from blood loss. And what of our mate with a 270 or 308 running some SSTs at a decent speed? Well the hind 150yd away has been completely flattened. The SST has arrived with over 2000ftlb of energy and caused massive damage to the lungs, and has also instantly incapacitated the hind. Was this caused by hydrostatic shock or some other mechanism? I have no idea but kinetic energy is a good thing!

The shock wave from a high velocity bullet cannot be underestimated for 'stunning' the animal which then bleeds to death and dies while laying on the ground. We have all seen a 'stunned' animal that we thought had been killed instantly, leap to its feet before the eight count and leave the ring. This 20 second link shows the shockwave: https://www.youtube.com/watch?v=osNWIP7tg3Y