killing power

[farmboy]

Do you like to see bullets exit a game animal or break apart and dump all the energy in the animal?

[gitano]

Be careful, please, when you ask questions that you know are controversial. It's best to lay some preliminary ground rules about the specific issues you are interested in, AND what is expected in kinds of answers.

This particular issue has literally caused fist-fights between people as 'famous' as Elmer Kieth (poke through holes), and Jack O'Connor (Mr. "kinetic energy" and a "keep it inside" kinda guy), as well as a few of us lesser mortals.

So, with that said, I'll answer your question with my opinions on this matter.

First, I do NOT believe that one or the other of these two positions is "right". BOTH are adhered to by people that know what they are doing as far as hunting goes. That said, there are idiots - most of them "gunwriters" (ptooey) - on both sides of this debate that don't know their elbows from a crow bar about the matter.

As a general rule, I like to "keep it inside". No small part of that preference is based on the fact that I like animal "parts" including skins and bones. One hole is better than two. For the first 30 years or so of my hunting and reloading life, I was a "speed uber alles" guy. I STILL have a GREAT deal of respect for speed.

However, after an "exciting" coastal brown bear hunt with a rifle that shot VERY fast and I referred to as the "ultimate firearm" BEFORE the hunt and the "sissy gun" AFTER the hunt, I purchased my first bigger than 7mm rifle, a .338 Win Mag. It's been 'downhill' - at least in speed ever since. I have developed a very real appreciation of "BIG AROUND". I still like them to "stay inside", but I LIKE "BIG around". AND, big around bullets don't NEED to go fast to hit like a "hammer".

I started a thread on terminal performance and the concept of "work". That concept explains how BOTH perspectives - slow, big around, and through and through vs fast, small, and keep it inside - can produce the SAME "dead right there" results.

SO... I "like" one hole, and I "like" dead right there. Whichever bullet "works" to that end is OK with me.

Paul

[sakorick]

Do you like to see bullets exit a game animal or break apart and dump all the energy in the animal?

I prefer the dump all the energy in the animal thought process.....but they are sure hard to track. I also like the bigger bullet concept. My 35 Whelen as an example. Here on my farm I have seats that afford shots up to 500 yards for those inclined to do so. My range limit is around 300 yards, however, the longest shot I have ever taken in my life is 277. This subject could take up hundreds of threads as the perfect cartridge/bullet combo has yet to be developed and probably never will, IMHO.

[farmboy]

Be careful, please, when you ask questions that you know are controversial. It's best to lay some preliminary ground rules about the specific issues you are interested in, AND what is expected in kinds of answers.

This particular issue has literally caused fist-fights between people as 'famous' as Elmer Kieth (poke through holes), and Jack O'Connor (Mr. "kinetic energy" and a "keep it inside" kinda guy), as well as a few of us lesser mortals.

So, with that said, I'll answer your question with my opinions on this matter.

First, I do NOT believe that one or the other of these two positions is "right". BOTH are adhered to by people that know what they are doing as far as hunting goes. That said, there are idiots - most of them "gunwriters" (ptooey) - on both sides of this debate that don't know their elbows from a crow bar about the matter.

As a general rule, I like to "keep it inside". No small part of that preference is based on the fact that I like animal "parts" including skins and bones. One hole is better than two. For the first 30 years or so of my hunting and reloading life, I was a "speed uber alles" guy. I STILL have a GREAT deal of respect for speed.

However, after an "exciting" coastal brown bear hunt with a rifle that shot VERY fast and I referred to as the "ultimate firearm" BEFORE the hunt and the "sissy gun" AFTER the hunt, I purchased my first bigger than 7mm rifle, a .338 Win Mag. It's been 'downhill' - at least in speed ever since. I have developed a very real appreciation of "BIG AROUND". I still like them to "stay inside", but I LIKE "BIG around". AND, big around bullets don't NEED to go fast to hit like a "hammer".

I started a thread on terminal performance and the concept of "work". That concept explains how BOTH perspectives - slow, big around, and through and through vs fast, small, and keep it inside - can produce the SAME "dead right there" results.

SO... I "like" one hole, and I "like" dead right there. Whichever bullet "works" to that end is OK with me.

Paul

i dont think you have to worry about the answers here i have not read a post that was not polite on this forum! Everyone seems a little more mature on here and confident in there ideas that they don t get mad if some one does not agree! I really like this group.

[farmboy]

I read an article on a TBBC sale slip about rotational speed adding  to killing power which i have found interesting. It was stated that rpm hardly slows down over long distances and that when a bullet starts to open the edges cut more with higher rpm. Where i have witnessed this in action or have thought so was shooting hares at long distance with a 17rem and a 222rem. Shot so far that there was less energy than a short distance shot with a 22 lr and yet the hares died quickly not like a hit from a 22 lr. Perhaps just a difference in the ability of the projectiles.

[farmboy]

I have liked the idea of big and fast with a hold together bullet. I saw one failure with that one time. A friend s first deer it was the last day i was baling straw and i saw a small whitetail buck gave him a call and he came over. He had a 300 win mag loaded with 180 grain partitions. I think he may have had a bit of buck fever anyhow he hit a hind quarter the deer took off then he put one through its chest and down he went. The interesting thing is the partition came apart and there was very little penetration even with the back part of the bullet it did not hit bone stopped in around 4 to 5 inches.

[Jamie.270]

I read an article on a TBBC sale slip about rotational speed adding  to killing power which i have found interesting. It was stated that rpm hardly slows down over long distances and that when a bullet starts to open the edges cut more with higher rpm. Where i have witnessed this in action or have thought so was shooting hares at long distance with a 17rem and a 222rem. Shot so far that there was less energy than a short distance shot with a 22 lr and yet the hares died quickly not like a hit from a 22 lr. Perhaps just a difference in the ability of the projectiles.

Uh-oh,....

Theorist gun writers and their obnoxious notions, PTOOEY!

The amount of rotational inertia, or moment of force, (AKA Torque)  that can be stored in something that weighs less than a gram, or a few grams, and whose diameter measures in fractions of an inch is miniscule.  Even at high RPM.

The energy stored in the bullet's forward acceleration is orders of magnitude  greater that what is stored in its rotating mass.

There is a reason why,  when engineers want to store rotational power/force, that they make flywheels as large  as the application will allow, and bias the mass of the flywheel near the  circumference.
Pretty much the opposite of a bullet.

[farmboy]

Uh-oh,....

Theorist gun writers and their obnoxious notions, PTOOEY!

The amount of rotational inertia, or moment of force, (AKA Torque)  that can be stored in something that weighs less than a gram, or a few grams, and whose diameter measures in fractions of an inch is miniscule.  Even at high RPM.

The energy stored in the bullet's forward acceleration is orders of magnitude  greater that what is stored in its rotating mass.

There is a reason why,  when engineers want to store rotational power/force, that they make flywheels as large  as the application will allow, and bias the mass of the flywheel near the  circumference.
Pretty much the opposite of a bullet.

yes never thought about the flywheel idea before you are right.

[Jamie.270]

Just a little math for an early morning exercise,...

The reason for the lack of energy in the rotating mass is two fold.
1) The lack of mass.
2) The lack of  actual distance the outermost diameter of the bullet is actually  traveling.
For instance:
The circumference of a .223 bullet is .700".  
So:
At 250,000 RPM the bullet jacket's rotational rate of travel is  175,000 inches per minute.
Or 14,583 feet per minute.
Or 243.06 feet per  second.

So even if all 55 grains of the bullet's mass  were located at the circumference, (which we know it's not, but we'll run  with that for the sake of the conversation) or outermost diameter, it is  still only (roughly) 2 grams, traveling at less than the speed of a projectile  from a Daisy Rough Rider BB gun.
Somewhere around 4.5 ft/lbs of energy, if my  early morning math is close.
Now, imagine how miniscule it would be in a .17  caliber slug that only weighs 25 grains.

There's some video around here somewhere that demonstrates clearly that the  notion of rotational assisted damage is pure theorist gun writer's  fallacy.
Otherwise known in the vernacular as: "A bunch of hooey"

I'll  see if I can find it.

[farmboy]

funny i just was working on the numbers for a 25 grain bullet and made the same assumption about the mass on the outside of the bullet!  http://www.engineeringtoolbox.com/flywheel-energy-d_945.html  this is what i was using.

[farmboy]

So the next question is. Do rifle barrels produce lower velocities with a faster twist rate as it is stated in some writings. EG a 70 grain bullet in a 6mm rem one at 1 in 9 twist the other at 1 in 12?

[farmboy]

And if they do how come? no energy or very little is used to turn that bullet faster.

[Jamie.270]

Here's the thread with the video link:
http://www.thehunterslife.com/forums/showthread.php?t=14137&highlight=frames

[farmboy]

thank you i will go watch it

[Hunterbug]

I prefer them to exit on elk for sure. They are tough animals and baring a hit that disrupts the central nervous system you aren't going to "shock" them down. I like having two holes to make as much blood trail as possible. With deer, I really don't care. They usually drop pretty quickly either way.

[Jamie.270]

So the next question is. Do rifle barrels produce lower velocities with a faster twist rate as it is stated in some writings. EG a 70 grain bullet in a 6mm rem one at 1 in 9 twist the other at 1 in 12?

The difference, while I'm sure is measurable, is indeed insignificant.  I suspect for the reason(s) you stated.
I'm sure an adroit Quickload user ( ) user would/could calculate it though.

[farmboy]

right around 5.50 it looks as though they are shooting a triple shock bullet and looks like the wound channel is shaped in a spiral from the petals of the bullet rotation. Not saying it is transferring energy because as you have stated and it is correct there in very little energy in the rotation. wondering if that shape of wound channel is better or worse?

[Jamie.270]

I saw that, and noticed the lack of rotation vs forward velocity, and the fact that it is a rather long bullet, with rather short petals.
Notice also @ 5:59 the pistol bullet that is clearly rotating as it enters the medium, and stops rotating as the petals open from expansion.
It would be worthwhile to know what that particular medium is.  It's not Ballistic Gelatin, and almost looks like water with cooking gelatin added.

[farmboy]

most of them did seem to turn slow in relation to forward speed a few were turning after the splatted on the steel as well

[farmboy]

I read some where a long time ago that the US army tested killing farm animals in relation to when they had eaten last and there was more damage on a full stomach than an empty one. That might have been in the ackley manual not sure right now

[gitano]

I'm loving the path this thread has taken!

i dont think you have to worry about the answers here i have not read a post that was not polite on this forum! Everyone seems a little more mature on here and confident in there ideas that they don t get mad if some one does not agree! I really like this group.

I'm really glad you think that, farmboy, but that's not by 'accident'.

Some time back, I got tired of the pontificating idiots (gunwriters - ptooey) spewing drivel about which they knew nothing and "did the math" on twist rate "using energy". I'll look for that thread. 'Til I find it, I'll summarize the numbers.

There IS a quantifiable difference in the energy leaving the muzzle of a rifle as a function of it's twist rate. However, it is measured in single digits of ft-lbs in the WORST cases. I can't recall if it was the largest calibers that were the worst-hit or the smaller, but what I do remember is that it was only at the extremes of twist rates - very high like 1:3 and very low like 1:30 - that it made any difference that even MIGHT be outside the normal shot-to-shot variation in muzzle velocity.

It is easy to conceive of the cause of more of the bullet's energy used by 'fast' twist, than 'slow' twist barrels. Consider the distance a bullet has to travel to exit the muzzle of a rifle with a barrel in which the distance from the start of the rifling to the muzzle is 24". The length of the barrel is effectively "extended" by the twist rate. It is easiest to "see" this if you imagine a single point on the outside of the bullet. In a barrel without rifling, that point would travel exactly 24" to exit the bore. However, rifle that barrel and you can see that that same point would travel farther. Now, the distance the bullet travels isn't the real issue. RESISTANCE is the issue. If a bullet has to travel farther, then the barrel will exert more resistance on it.

Resistance is difficult to measure, BUT, it is a linear function of the DISTANCE over which it is applied. Therefore, simply calculating the ratio of the differences in the twist rates will provide the ratio of the difference between resistance caused by the faster twist rate. This is what stupid gunwriters (ptooey) do, and more significantly where they STOP their evaluation because they don't know how to calculate resistance.

It is easy to see how someone could look at those ratios and insufficiently conclude that "faster twist rifling uses more of the bullet's energy". HOWEVER, while using ratios is a good way to determine the relationship between two factors, it does not provide the absolute MAGNITUDE of the effect. Here's an abstracted example: It is quite common these days to hear something like "This new sport (X) is the fastest growing sport in the nation." My response to that is a yawn because if sport X had only two players yesterday, and today it has 4 players, it has increased ONE HUNDRED PERCENT (a proportion or a ratio) IN ONE DAY. However, the number of players of Little League Baseball could increase by FOUR HUNDRED in one day and it wouldn't be an increase of even ONE PERCENT. "Fastest growing" sport, or religion, or internet site, or business, or ANYTHING, is meaningless if the ABSOLUTE numbers of the people participating isn't given.

So, what does this mean with respect to rifling and a bullet's energy? Just this. Even though the EXTRA distance traveled by a bullet in a 1:8 twist barrel is twice the distance traveled by a bullet in a 1:16 twist barrel, that extra distance is MINUSCULE in absolute magnitude and therefore, the effect on the bullet's departing velocity (and therefore kinetic energy) is also MINUSCULE.

I'll find the spreadsheet so "you" can see the actual numbers.

Paul

[farmboy]

That's all logical. And understandable. It would be interesting to measure muzzle velocity loss going to shorter barrels at different twist rates. Maybe It would make a difference or not fun to try problem being they would be different barrels.

[farmboy]

The other thing to remember about gun writers is there job is sales. They exist to sell magazines which in turn sell ads. They just have to sell not writing technical papers. Some of them are fun to read though. The good ones you feel like you are in the woods beside them.

[gitano]

Well, I would agree that it would be interesting to consider, but we can 'do some math' and conclude that other variables have so much more influence, that the twist rate 'experiment' wouldn't be necessary.

Here's the math:

The energy imparted to a bullet is a linear function of the area under the pressure-time (or pressure-distance) curve. Here's a typical P-D curve.


The red line is pressure and the blue line is velocity. The area under either curve - but particularly the velocity curve - is proportional to the energy of the bullet at any instant in time. THEREFORE, if we were to calculate what the area under the last one inch of bullet travel was, we would find that the energy loss associated with cutting one inch off of the barrel would be HUGE relative to the reduction in resistance due to rifling realized by the same one inch of barrel length loss.

Paul

[farmboy]

Maybe I was not clear enough or do not understand. What I was thinking would a fast twist rate barrel lose less speed if it was an inch shorter than a slow twist barrel after an inch was cut of of it as well. But thinking about your chart the rotational distance would not matter it would be it forward distance that would determine the loss.

[gitano]

Fast or slow twist rates wouldn't matter, mostly from a practical point of view, but from a theoretical as well. One cannot change the twist rate of a barrel and maintain the caliber. On a theoretical level, if one chose a "fast" twist in anticipation of some day shortening the barrel and wanted to ensure that they would lose the least amount of MV, they would be wasting their time. The difference that changing the twist rate would have on MV is WAY inside the shot-to-shot variability on even benchrest rifles let alone over-the-counter ones. Let me put this another way:

Let's say you have two rifles chambered by the same gunsmith using the same reamer in the came cartridge with the same length barrels made by the same barrel manufacturer EXCEPT that one of them has 1:6 twist rifling, and the other has 1:12.  Let's say both rifles have a load that propels a 180-grain bullet at AN AVERAGE 2800 f/s out their muzzles. That average muzzle velocity is calculated by taking the average of MANY shots. In addition to the average value, there is also a standard deviation associated with that average value. The standard deviation gives an idea about how PRECISE the ESTIMATE of the "expected value" (AKA "average") is. My personal experience is that the a common value for the standard deviation of a bullet with a MV of about 2800 f/s is about 12 f/s. That means that the TRUE value of the "expected value" (or average) CAN NOT BE DETERMINED WITH CERTAINTY TO LIE ANYWHERE BUT THE RANGE BETWEEN  2775 f/s and 2825 f/s. A RANGE of 50 f/s.

That means that from shot to shot, one can be fairly certain that 95% of the shots fired will have a MV between 2775 and 2850 f/s.

The magnitude of the difference caused by the difference in twist rates is between about HALF a foot per second, to about 1.5 f/s. Therefore, the variance of the muzzle velocity DUE TO FACTORS OTHER THAN TWIST RATE is about 35 times HIGHER than the effect of the difference in twist rate. In other words, you would never be able to "see" the effect of changing the twist rate because the "natural" variation of muzzle velocity caused by other factors would COMPLETELY swamp the twist rate effect.

Paul

[gitano]

Here are the spreadsheets I referred to above:

This one shows the "extra distance" that a bullet has to travel due to twist rate. The barrel length for all calculations is 24".


This one is calculating the proportion of energy associated with rotational movement relative to the translational (along the barrel) movement energy.


The above is for sort of "average" twist rates for the specific caliber. The next spreadsheet shows the calculations used to derive the numbers, and the results for twist rates that are VERY "fast" for the given caliber. Therefore they are "worst case" figures.


Paul