Rotational velocity vs wound severity

[Pdvdh]

Opinions on this topic run the gamut. I'm trying to locate some opinions that seem to merit greater consideration than the common opinion. Here's another interesting post on another forum: P O Ackley and bullet rpms - 24hourcampfire

Re: P O Ackley and bullet rpms [Re: Ol` Joe]
AussieGunWriter Offline
Campfire Guide

Registered: 05/31/05
Posts: 3969

I have touched on this subject briefly at the fire before, because it was my observation during feral animals culls comparing various cartridges in the same caliber, that when the impact velocity was equal, meaning that say a 200 yard shot with a 7x57 was equal to a 7mm Remington @ 320 yards, the cartridge starting faster usually was the more emphatic killer overall.

I tried this with many calibers, .243 Vs .240 Weatherby, 270 Win Vs the Wea version, .308 Vs 300 Win, .30/06 Vs .300 RUM .25/06 Vs 257 Wea and some other combo's.

It wasn't until I got to .338 caliber comparing .338, .340 and .338/378 that the differential was not obvious with medium sized game.

With the .458 Vs the .460 that I found I needed larger animals to do the same comparison against and when the body weight got up to 1000 pounds or more, again, this phenomenon became noted.

Having said all this, I have for some decades now, believed that the rotation of a bullet had influence on the terminal performance of a bullet. I am no scientist and cannot qualify it more than to say that I killed thousands of animals in coming to this conclusion.

AGW

 

[elkaholic]

Opinions on this topic run the gamut. I'm trying to locate some opinions that seem to merit greater consideration than the common opinion. Here's another interesting post on another forum: P O Ackley and bullet rpms - 24hourcampfire

Re: P O Ackley and bullet rpms [Re: Ol` Joe]
AussieGunWriter Offline
Campfire Guide

Registered: 05/31/05
Posts: 3969

I have touched on this subject briefly at the fire before, because it was my observation during feral animals culls comparing various cartridges in the same caliber, that when the impact velocity was equal, meaning that say a 200 yard shot with a 7x57 was equal to a 7mm Remington @ 320 yards, the cartridge starting faster usually was the more emphatic killer overall.

I tried this with many calibers, .243 Vs .240 Weatherby, 270 Win Vs the Wea version, .308 Vs 300 Win, .30/06 Vs .300 RUM .25/06 Vs 257 Wea and some other combo's.

It wasn't until I got to .338 caliber comparing .338, .340 and .338/378 that the differential was not obvious with medium sized game.

With the .458 Vs the .460 that I found I needed larger animals to do the same comparison against and when the body weight got up to 1000 pounds or more, again, this phenomenon became noted.

Having said all this, I have for some decades now, believed that the rotation of a bullet had influence on the terminal performance of a bullet. I am no scientist and cannot qualify it more than to say that I killed thousands of animals in coming to this conclusion.

AGW

Paul.....If you read on down the same thread to the same poster (pg. 3) he gives an even better description of what I suspect.....Rich

 

[barnesuser28]

I think a thin jacketed bullet like a berger and a non jacketed solid copper bullet like a Barnes would cause more damage from an increase in rpm on impact.

I think on a bonded bullet like the accubond, it wouldnt matter much.

Correct me if im wrong because i probably am but i think the higher rpm on impact for a thin jacketed bullet would create more centrifugal (spelling?)force causeing the jacket and some lead fragments to spread outward creating a wider wound channel.

And a Barnes would benefiet because the petals would grab more flesh and do more tearing the faster it spins, causing a wider wound and draging vital tissue along with it.

Now an accubond does its damage by pushing tissue away rather than tearing it so the increased rpm wouldnt be of much help.

Thats the way i think of it, again i havent proven this but i think this a logical answer.

Riley

 

[Pdvdh]

Paul.....If you read on down the same thread to the same poster (pg. 3) he gives an even better description of what I suspect.....Rich

Another interesting post from AussieGunWriter


Re: P O Ackley and bullet rpms [Re: 9point3]
AussieGunWriter Offline
Campfire Guide
Registered: 05/31/05
Posts: 3969

Originally Posted By: 9point3
The next thing that needs discussed is how many RPMS are lost during flight? I bet it is not that many. If this is the case, are not the tests skewed a bit when one loads his bullets at a lower rate to simulate impact velocities?

Sure the impact velocity is correct but isn't the impact RPM wrong?


I believe you are correct 9.3. I have noted this before and also feel that simulated tests are not representative of actual bullet performance at "slower" velocity as compared to "reduced" velocity which is not the same thing.

Many years ago I did some reduced reloading for my son when he was about 8 years old to reduce the recoil of a .30/06. I loaded back 165 grain bullets (Hornady Spire points) to 2400 fps muzzle velocity and got them to shoot quite well at the range.

When these same loads were shot into animals at 2-300 yards they were dismal killers with complete penetration and loss of expansion and tissue disruption. Yet, we all know how wonderful cup and core 165 grain bullets are at usual '06 velocities with medium game.

I totally disregard simulated bullet expansion tests in artifical medium with reduced muzzle velocites, as I believe through field experience that retained bullet spin, has a contributing factor in bullet expansion as well as stability in flight.

Additionally, I also believe that the velocity of penetration has an influence on killing effect.

AGW
______

 

[elkaholic]

I think a thin jacketed bullet like a berger and a non jacketed solid copper bullet like a Barnes would cause more damage from an increase in rpm on impact.

I think on a bonded bullet like the accubond, it wouldnt matter much.

Correct me if im wrong because i probably am but i think the higher rpm on impact for a thin jacketed bullet would create more centrifugal (spelling?)force causeing the jacket and some lead fragments to spread outward creating a wider wound channel.

And a Barnes would benefiet because the petals would grab more flesh and do more tearing the faster it spins, causing a wider wound and draging vital tissue along with it.

Now an accubond does its damage by pushing tissue away rather than tearing it so the increased rpm wouldnt be of much help.

Thats the way i think of it, again i havent proven this but i think this a logical answer.

Riley

Don't know? But I hope to find out......Rich

 

[barnesuser28]

Rich, PM inbound

EDIT: you need to delete a couple pm's, i cant send one.

 

[Catfur]

Based on the previous quoted information, the 7mm bullet in question, at 1000 yards, is experiencing a radial acceleration of over 1M m/s^2. Remember that a lead bullet literally flies apart under these forces, we are talking about a serious additional forces pushing the bullet to expand (even a solid).

 

[Pdvdh]

Catfur,

Not certain that I understand your comment, but I don't believe there is any additional rotational acceleration of the bullet after it leaves the muzzle. The rotation of the bullet (rpms) decreases (decelerates) after the bullet leaves the muzzle, but the rate of rotational deceleration is much less rate than the linear deceleration of the velocity (ft/sec) of the bullet. I think someone provided a calculation that showed the rpms of rotation decreased by about 21% at 1000 yards, compared to the rpms of the bullet at the time it left the muzzle.

 

[Catfur]

Catfur,

Not certain that I understand your comment, but I don't believe there is any additional rotational acceleration of the bullet after it leaves the muzzle. The rotation of the bullet (rpms) decreases (decelerates) after the bullet leaves the muzzle, but the rate of rotational deceleration is much less rate than the linear deceleration of the velocity (ft/sec) of the bullet. I think someone provided a calculation that showed the rpms of rotation decreased by about 21% at 1000 yards, compared to the rpms of the bullet at the time it left the muzzle.

I'm talking about the internal forces on the bullet, the force the metal composing the bullet (which is spinning very rapidly) experiences. As it spins, the metal is undergoes centripetal acceleration, which is what keeps it moving in a circle. While the rate at which the bullet spins may decrease, the individual bits of the bullet are still experiencing centripetal acceleration (and always will as long as it's spinning at all).

 

[Joe King]

I'm talking about the internal forces on the bullet, the force the metal composing the bullet (which is spinning very rapidly) experiences. As it spins, the metal is undergoes centripetal acceleration, which is what keeps it moving in a circle. While the rate at which the bullet spins may decrease, the individual bits of the bullet are still experiencing centripetal acceleration (and always will as long as it's spinning at all).

I like to call that the "merry go round effect" sitting just off center of a merry go round it pretty easy to stay put, sitting out on the edge it wants to throw you off, even though the rpms stay the same. having kids is fun

 

[Catfur]

... having kids is fun

Until they decide to try physics experiments on the merry-go-round, and fling themselves off it at high speed and into the emergency room, by way of high speed impact...

 

[Joe King]

Until they decide to try physics experiments on the merry-go-round, and fling themselves off it at high speed and into the emergency room, by way of high speed impact...

hey I was that kid................. thank god I survived it

 

[Lefty7mmstw]

Until they decide to try physics experiments on the merry-go-round, and fling themselves off it at high speed and into the emergency room, by way of high speed impact...

The find a culvert head first and break your arm or jump out of a shopping cart to see how big a knot on your head you can get experiments were tried my my oldest kid. My younger kid hasn't tried any personal destructive physics yet(cross fingers, toss salt over shoulder, knock on wood).

 

[6.5shaggy]

This is a very intriguing topic, and one which I also very firmly believe in. I used an AR15 .223 1-9 twist for wild hogs for a couple years, then I switched to a 22PDK 1-8 twist AR15 with a gain of 300 fps mv with the same bullets. I know the impact velocity is higher, but marginal at any extended distance. The instantainious death rate is much higher with the PDK, much like when I used a .220Swift with a 1-14 twist. This is an example of a light varmint bullet on large tough animals. The instant death is not from deeper penetration or greater tissue destruction judging by disecting the animals, thus leading one to feel it is increased shock. But the increase of 100 fps impact velocity doesn't seem enough to boost shock to phenominal killing levels leaving me to think it is rotational velocity that is coming into play.

I remember when I was in high school and we would get watermelons from the local fiels and go "melon rollin". We would lay down on the tailgate of the pick-up while someone would drive and gently lay the melon on the hi-way. They would slide at first, then begin to roll. After a while when the rps got high enough the melon would EXPLODE and sometimes throw watermelon as high as the powerlines. The optimal speed was 60 mph, any less and the "spectular-ness" was less, any more and abrasion in the "slide" phase wouldn't allow rpms to get very high before rupture.

Now that is about as scientific as it gets. Elkoholic, I think I may have inadvertly ended your study. LOL

PS: feel free to roll melons on your own, but do so at your own risk!