Thread: Something interesting re temporary cavity

Because some of the discussions over the last months have ben very interesting, and it's on my mind.

Ive mentioned using my favourite high shoulder shot on a whitetail buck at close range with a heavy slow projectile, and not getting the result I would usually expect of a deer dropping on the spot. Yet projectile went almost right through animal and permanent cavity damage was acceptable.

This vid from Bryan Litz is interesting. Look at what the temporary cavity and energy do too the material underneath the Gelatin block.

https://www.facebook.com/watch?v=2127561314312349


edit- just realised I stuck it In wrong forum. Should have been in reloading and ballistics. Mods feel free to move if you wish.

Yep - the hydrostatic shock can indeed break bones. The tissue may bounce back, but nerves are often severed and broken bones will not suddenly be fixed! If you take a shot at a 5 litre bottle filled to the brim with water, sat atop a concrete block, it will usually result in a broken block and spectacular splash.

The temporary elastic deformation exceeds the yield strength of the thin/brittle sheet underneath. You can see this on plastic bucket lids too when you place gelatin blocks on those and shoot them. Plywood doesn't suffer any harm.

what is the secondary explosion at 0;21 ?

Originally Posted by HILLBILLYHUNTERS

what is the secondary explosion at 0;21 ?

Air sucked into the temporary cavity combusting - compresses to high pressure rapidly as the cavity collapses with the elastic deformation of the gel rebounding

Originally Posted by gimp

Air sucked into the temporary cavity combusting - compresses to high pressure rapidly as the cavity collapses with the elastic deformation of the gel rebounding

DAmn...so when something gets shot, first it has to deal with the sudden appeareance of a hole where there wasn't one and having it feel like a ballon was inflated in there, before they can even figure that out, there is a sponteneaus explosion inside the hole just to add insult to injury.......

Making a rough estimate of the gel block size going off other vids, Id say 500mm long by 150x 150. That gives the block a rough weight by volume of water, of 11kg. the timber slates underneath it have to be strong enough with a margin to support that weight and not bend at all. They appear to be about 5mm when compared to projectile diameter. they look to be timber due to the way they break along the grain.
Rupture is at the point of largest energy output.
Im not concluding that would or would not break bone. But its a sizeable shock too the internal system of an animal that might well help immobilise it long enough for the permanent cavity to do its work.

Originally Posted by gimp

The temporary elastic deformation exceeds the yield strength of the thin/brittle sheet underneath. You can see this on plastic bucket lids too when you place gelatin blocks on those and shoot them. Plywood doesn't suffer any harm.

Yes. I think this is what happened to the stag I shot this morning. The temporary elastic deformation (caused by the bullet) exceeded the yield strength of the stags nervous system causing it to fall over. Unfortunately, I could not observe this in the dead animal like you can with a plastic bucket lid.

Originally Posted by Shearer

Yes. I think this is what happened to the stag I shot this morning. The temporary elastic deformation (caused by the bullet) exceeded the yield strength of the stags nervous system causing it to fall over. Unfortunately, I could not observe this in the dead animal like you can with a plastic bucket lid.

Excellent. Where'd you hit him ?

Originally Posted by gimp

Excellent. Where'd you hit him ?

Low in the neck, front on. I haven't had a look at the internal physical damage yet but will report back when I have.

I find it all really interesting. I shot maybe a hundred big game animals not including goats with compound and longbow. I can only recall 2 dropping immediately even though a number were shot through one shoulder blade. So reasonably large permanent cavity but very little, or very slow shock and energy transmission.

Ive only shot the one animal with a large projectile going slow, but also seen a few shot with 300BLK. Not huge numbers and could be shot placement too. But results have been similar. Again I don't seem to see the bang flops Im used too.

My general observation is that bigger fast expanding projectiles at speed, seem to transmit a lot of shock too an animals system that seems to at least initially drop the animal.

And Ive definitely noticed that big animals such as sambar, tend to'Behave" better, when hit by bigger fast projectiles.

But then there are Im aware other factors as well.

I have a common but weird heart condition. proximal Atrial fibrillation. Occasionally as in once every 15 years or so, My heart will go out of rhythm. Speed up to 180bpm and then randomly miss a beat or two and put in some big ones to compensate. Those missed beats for around a second or so immediately take all the energy out of me in an astounding fashion!

All that to say, who knows what temporary effect such a destructive event as an expanding projectile at close too or over the speed of sound, that can break timber near it, could be having on the nervous system.

Actually rewatching the video. the expansion is not only breaking the base at its peak.its also shearing it off where it contacts the base block in a different and cleaner manor.

I butchered the stag I shot this morning and had a good look at what damage was done.
Tha bullet entered low in the neck and ended up on the outside of the right shoulder.
Firstly, blood and bruising on the outside of the right shoulder. The exterior of the muscle was intact and the skin was undamaged.
Attachment 263177
The right shoulder bone was smashed to bits.

The inside of the rib cage showed two small contusions on the right hand side under the shoulder but as far as I can see there is no physical damage to the spine.
I did not find any part of the projectile.

BTW, the deer dropped on the spot while it's bigger mate ran off. As it lay there, 100 yards away, I could see it trying in vein to regain it's feet so I shot it in the head.

Can you give a run down of what you think has happened? From reading that it sounds like the deer had some ability to move but couldn't get up. Did the projectile break any bone in the neck where it entered? Was there any damage to heart/lungs?

It appeared no bone in the neck was damaged. The bullet went under the spine from the front (by some margin) and the tissue/bone damage ended in the right shoulder.
It's legs disappeared from under it at the shot and once down only seemed to be able to lift it's head. Nothing more. Lungs were damaged.