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Muzzle energy.....
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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Ominivision1
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PostPosted: Sun Apr 24, 2011 8:42 pm    Post subject: Re: Muzzle energy..... Reply with quote

slimjim wrote:
Pumpkinslinger wrote:
Slim, in your example, which one would do the most tissue damage?

I think that would depend on the bullet design. I expect my 405gr laser-cast lead bullets for my .45-70 would not expand but still be sufficient. A modern .45-cal bullet that opens up on impact would be impressive. A .30-cal bullet that expands while retaining its mass is the one I think would do the most tissue damage and provide the deepest penetration. Just an opinion that could spark further debate.

Slim you just opened up another can o worms.. Very Happy

But heres my thought on it. With equal sectional density the smaller diameter bullet with an equal mushroom ratio & weight retention & with more velocity, it should then penetrate deeper than the larger diameter bullet with a lower velocity. Smile

But the point is that the fat stubby round of a 45-70 may not look impressive next to some ultra modern high speed rounds but it really performs. I made bang flop kills on 1 black bear and 1 elk with it as well as quite a few deer.

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Elvis
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PostPosted: Sun Apr 24, 2011 11:48 pm    Post subject: Re: Muzzle energy..... Reply with quote

gee wizz how deep do you want to penetrate....
bunny wabbits 100mm through
bambi 300mm- 800mm
dumbo 1000+mm
all broadside I admit
all things need a relitivaty
do this maths a .22lr round into a bunny rabbit
now give a equivalent amount of mass/energy/ftpounds bla bla bla on a 140lb deer.

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PaulS
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PostPosted: Mon Apr 25, 2011 10:59 am    Post subject: Re: Muzzle energy..... Reply with quote

Momentum is the amount of force it would take to stop the bullet.
Or the maximum amount of force the moving bullet can impart to a target.
The ballistic pendulum is used to measure this force.
It is calculated as:
Mass x Velocity = slugs (momentum)
Mass = weight / G
Velocity in Feet per seconds
or
pounds x velocity = Foot Pounds (momentum)
7000 grains per pound - 165 gr = .02357 pounds

a 165 grain bullet at 2800 fps has 66 foot pounds of momentum (or 2.x slugs)

Penetration is a function of the bullet's form and it's velocity. It can be approximated using momentum, it's mass and ballictic coefficient in water.


Energy is a calculation of the theoretic maximum amount of work that can be done.

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Pumpkinslinger
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PostPosted: Mon Apr 25, 2011 3:32 pm    Post subject: Re: Muzzle energy..... Reply with quote

Sorry, I've got to be picky about the units and definitions here as that is part of the original confusion.

A "slug" is a unit of mass. en.wikipedia.org/wiki/Slug_(mass)

A 165 grain bullet has a mass of (165 grains / 7000 grains/pound / 32.17 ft/sec/sec =) 0.000733 slugs

Momentum equals mass x velocity.

The bullet's momentum at 2800 ft/sec would be (0.000733 slugs x 2800 ft/sec =) 2.05 slug-ft/sec

"Foot-pound" is a unit of energy, not momentum. en.wikipedia.org/wiki/...d_(energy)

Kinetic energy equals 1/2 mass X velocity squared.

A 165 grain bullet moving at 2800 ft/sec has a kinetic energy of (.000733 slugs/2 X 2800 ft/sec X 2800 ft/sec =) 2872 foot-pounds

Force equals mass x acceleration and we measure it in pounds. Weight is a force due to the acceleration from gravity.


Stovey, am I helping or hindering here? I know what I'm trying to get across but may not be doing a good job of communicating it.

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Pumpkinslinger
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PostPosted: Sat May 07, 2011 10:13 pm    Post subject: Re: Muzzle energy..... Reply with quote

I wanted to follow up on this thread because, as others have pointed out, muzzle energy and momentum are not magic numbers in regards to terminal ballistics. You have to take into account the bullet's construction.

I think the best way to illustrate this is to imagine taking two different bullets of the same diameter and weight and load them so they have the exact same impact velocity. Say we use a Barnes "Varmint Grenade" (VG) and a Barnes TSX, both .224 caliber and both weighing 50 grains. If I load them both so that they are going 3000 ft/sec at 100 yards they both have an energy of about 1000 foot-pounds and both have a momentum of about 0.67 slug-ft/sec.

The VG is designed to blow up on impact and Barnes' web site has videos showing this type of bullet coming apart after hitting something as insubstantial as a grape. The TSX, on the other hand, is designed to stay together and penetrate. The Barnes web site also has video of this type of bullet penetrating a block of ballistic gel.

If we shoot either of these bullets at a small critter, like a ground hog, either one would be effective. But if the target was something the size of a deer we'd have a different story. With the same shot placement the VG would produce a shallow wound, as it was designed to do, and might or might not kill a deer. However the TSX would stay together and penetrate on into the vitals, as it was designed to do, and produce a clean kill.

My whole point here is that you can't just dismiss the very real physics involved in the terminal ballistics but you also have to take into account the other variables, such as bullet construction and shot placement, in order to make valid comparisons.

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inthedark
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PostPosted: Sat May 07, 2011 11:36 pm    Post subject: Re: Muzzle energy..... Reply with quote

I just received my "Cartridge Comparison Guide" by Andrew Chamberlain ISBN 0-9790335-2-7 in the mail yesterday. It is an interesting read so far and goes into extreme detail in the area of what to consider when selecting a cartridge. It has both rifle and handgun data tables. It s purpose is to educate the reader on how to gain the maximum benefit from a personalized cartridge selection. (Their words not mine. I don't speak that elequently) in a nutshell is describes the calibre, cartridge and bullet types in combinations so that the reader may make an informed choice in what to reload for a specific purpose i.e. a 100lb woman who wants a rifle/cartridge/bullet combination for hunting black tail deer in the mountains, or a 200lb man who is hunting cape buffalo in a South African swamp. It has several appendices describing everything from identifying game animal's physical structures to felt recoil. I be liking it!

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jcruthis
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PostPosted: Tue Jul 12, 2011 9:35 pm    Post subject: Re: Muzzle energy..... Reply with quote

i didnt read this whole thing but to put simply...2500lbs/sq ft of energy when you look at the diameter of the projectile aint alot ex 30 cal bullet is .308 the area of that is about .074sq inches...im too lazy to do all the math but if you had 168gr projectile that was 1sqft of surface area with 2500lbs/sqft...well im not a very elloquent speaker (or typer) but you see what im sayin...i hope... thats why expansion is so inportant
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PaulS
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PostPosted: Thu Jul 14, 2011 8:47 pm    Post subject: Re: Muzzle energy..... Reply with quote

That is 2500 foot pounds of energy not 2500 pounds per square foot.....
which woulb 2500/144 per square inch or somewhere near 6 pounds of energy in a 50 caliber bullet.

The bullet actually has 2500 foot pounds of energy - which roughly means that it could swing 2500 pounds one foot if it was hanging on a pendulum and there was no deformation or heat produced in a perfect collision between the bullet and the weight.

Energy is a theoretical evaluation derived from the amount of velocity and the mass of the bullet. there is very little correlation between the number and anything physical in the real world.

Point in fact:
A one gram sewing needle and a 1 pound iron ball can be given the same amount of energy with the application of the correct velocity - I would take a hit with the sewing needle over the iron ball any day. the damage done has more to do with the mass and diameter of the projectile than the amount of energy.

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Pumpkinslinger
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PostPosted: Fri Jul 15, 2011 9:18 am    Post subject: Re: Muzzle energy..... Reply with quote

Given the same energy of 2500 foot pounds:

A 1 pound ball would have a velocity of 401 ft/sec.

A 1 gram needle would have a velocity of 8,546 ft/sec.

A 55 grain bullet would have a velocity of 4,527 ft/sec.

A 165 grain bullet would have a velocity of 2,613 ft/sec.

A 225 grain bullet would have a velocity of 2,238 ft/sec.

A 400 grain bullet would have a velocity of 1,679 ft/sec.

A 250 pound man would have a velocity of 25 ft/sec (17 mph).

A 3000 pound car would have a velocity of 7 ft/sec (5 mph)

Etc...

Each and every one of those would produce EXACTLY the same amount of work. Obviously the type of work would differ. Some produce more heat, noise, etc. Of all of them I think I'd prefer to be hit by the car!

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slimjim
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PostPosted: Sat Jul 16, 2011 6:02 pm    Post subject: Re: Muzzle energy..... Reply with quote

It would certainly be easier to get out of the way of the car!

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SingleShotLover
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PostPosted: Sun Jul 17, 2011 10:39 am    Post subject: Re: Muzzle energy..... Reply with quote

This is a fascinating discussion full of well-reasoned arguments and data. These issues are what make our sport so interesting. They also point out the fact that many terms and statistics are applied routinely to shooting even when they are flawed simply because there is no other way to express them.

Having been forced to take a statistics course in college (and despising it the whole time except for time spent pondering the relevant, and rather splendid, statistics of the blonde seated two rows in front of me) about the only thing I truly remember from the class was the first day. The professor opened his lecture with a quote from Andrew Lang: “He uses statistics as a drunken man uses a lamp post; for support rather than for illumination.” The point of the quote of course being that statistics can be (and often are) used merely to support a pet theory rather than revealing the truth of the subject.

That is what we as shooters are stuck with. We borrow statistics and measuring units from other disciplines to try to quantify various aspects of bullet flight, impact and etc. This is OK as long as we understand that they do not present the definitive answer but merely a good yardstick to compare various cartridges and their expected performance.

Jim Taylor did an excellent physical test that shows that our expectations when using "foot-pounds of energy" see no real value in the real world.
www.leverguns.com/arti...or/hit.htm
In his free-pendulum testing he found that even the 45/70 only moved it 5 1/2 inches. Pretty obviously diameter and momentum are more important than fpe for our uses.

As to the amount of recoil; there are many other considerations to be included before it affects the shooter's shoulder. First, that recoil is spread over a much larger area when transmitted to the shooter (roughly 7.5 square inches on a medium-sized rifle). This makes that theoretical 2,500 fpe become 333 and a whole bunch of decimal places per square inch of "energy" at the butt.

Add to that the fact that in order to reach the shoulder, that energy impulse has to first move an average 8 1/2 pound rifle from a dead-stop to full momentum and that figure drops quite a bit. Remember that the recoil is not in a linear manner but off-set by the drop of the comb which allows the firearm to rise, the shooter normally would maintain a firm grip, the upper body would normally "give" with the recoil impetus and the incredible friction of the bullet traveling up the bore acts to actually pull the rifle forward for a brief instant and that 333 fpe is quickly reduced to much more manageable real-world levels.

Never short-change the upper body movement when considering recoil management. A .460 Weatherby can be managed (at least for a couple shots!) if the body is allowed to sway with the recoil. Shoulders and collar-bones can (and have) been broken when fired with the shoulder supported against movement by a tree trunk or other firm object.

Bottom line is that bullets kill game in one, and only one, manner; causing sufficient tissue damage to vital tissues and organs to shut down neurological and other life-support functions. That bullet still has to get on target accurately and have the ability to penetrate to and through those same tissues or organs.
Whether we call it energy, momentum, penetration or even black magic, we have to figure a way to do the job the best way we can.

But let's still argue and reason...who knows? Maybe someone will come up with a formula that actually means something in our pursuits!

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slimjim
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PostPosted: Sun Jul 17, 2011 7:24 pm    Post subject: Re: Muzzle energy..... Reply with quote

Thanks, SSL, for furthering the discussion! I've got a .45-70 so I may have to try this tests in the link you provided. Also, your points have made me consider loading my .40-cal pistol with heavier bullets.

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Pumpkinslinger
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PostPosted: Sun Jul 17, 2011 8:15 pm    Post subject: Re: Muzzle energy..... Reply with quote

Ballistics is a physics problem, not a statistics problem. At this point I'll just recommend, once again, "Understanding Firearm Ballistics" by Rinker.

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SingleShotLover
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PostPosted: Mon Jul 18, 2011 5:46 am    Post subject: Re: Muzzle energy..... Reply with quote

Pumpkinslinger wrote:
Ballistics is a physics problem, not a statistics problem.

No argument there. I agree completely that ballistics should be strictly a problem of physics derived by empirical testing. Unfortunately pure ballistic physics has become corrupted in general use by some of the statistical information introduced to "simplify" predicting performance. It is in the process of this simplification that things become muddied when individuals accept the statistical analysis as absolute values.

Though there are many others, the three most commonly used and abused statistical devices that come to mind are:

SECTIONAL DENSITY offers a mathematical method of looking at the theoretical performance of a bullet. It is a product of the bullet weight and diameter (caliber). From this number various conjectures concerning ballistic performance comparisons can be made with some degree of accuracy. The flaw is that no provision is made for the actual bullet construction to differentiate between two otherwise identical bullets; jacket thickness, core material and etc. As with any mathematical or theoretical method, only cold hard facts obtained by actual field use can verify performance, but sectional density can give us a look at where to start and what to expect as to performance when considering various bullets and styles.

BALLISTIC COEFFICIENT is a statistical method of predicting the flight of a particular bullet. It is a product of bullet weight/bullet length/bullet velocity and is expressed as an absolute number such as .238. In theory the higher the ballistic coefficient the more efficient (flatter shooting) the bullet when compared with those of lesser BC. This is misleading since in actual practice ballistic coefficient varies with velocity, humidity, barometric pressure and altitude. A bullet that leaves the muzzle with a BC of .410 at 3,200 fps may only have a BC of .380 (for example) when the muzzle velocity is decreased to 2,700 fps. High altitudes can dramatically increase BC. Bullet shape also plays into the equation when figuring BC. Pointed bullets and those with boat tails usually rate higher than those with round noses of the same weight. This is because round nosed bullets tend to be considerably shorter than pointed, and length within a weight range increases BC. In general ballistic coefficient is most useful as a guideline of what can be expected or as a correlation between comparable bullets at comparable speeds.

STANDARD DEVIATION is nothing more than the statistical study of a load's velocity averaged over several shots. In theory, the lower the deviation the more accurate the load. In the real world this is not necessarily true. Standard Deviation is a pretty statistical toy…but not really good hard evidence. Far too many times we find loads that shoot extremely small groups that have relatively high numbers while those with lower numbers often perform poorly. This seems to be particularly apparent with some handgun loads but pops up in many rifles as well. I have spoken with many others who have experienced the same phenomenon. It actually shouldn’t be all that surprising…what we see is nothing more than examples of random distribution, more commonly known as a Bell Curve. It is an interesting picture but really only demonstrates a phenomenon rather than truly useable information.

Statistics can be well meaning or self-serving. Their conclusions are often determined by what the formulator's bias wants them to be. We should indeed try to stick to pure ballistic physics that has been proven by rigorous controlled testing.

Thanks for the recommendation of Rinker's book. I have added it to my "To Read" list!

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Elvis
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PostPosted: Tue Jul 19, 2011 1:38 am    Post subject: Re: Muzzle energy..... Reply with quote

the sharp shooter written by Matt and Bruce Grant
Covers this recoil vs projectile energy really well. they set up a target that could move with a pencil set to scribe how far it moved. then shot target ,held buttplate against target and fired and also threw a cricket ball into target. the ball had the most ooomph!!!

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