Muzzle energy vs. momentum

[Don]

Opening a can of worms here I know but when I was comparing momentum of my BP derringer loads to modern cartridge loads I was surprised by how well the BP loads compared. So what do you guys buy into as far as whats more important, muzzle energy or bullet momentum?

Don

 

[Darkgael]

I'm not exactly sure what you mean by momentum of bullets or how it's measured. Do you mean the difference between a heavy bullet moving slowly and a lighter bullet moving quickly? Or is it something else entirely?
This thread from a physics forum may help: http://www.physicsforums.com/showthread.php?t=72973
Pete

 

[BrownBear]

I don't like either. I prefer whompability.

Do a search here on the forum for some very interesting reading.

 

[Don]

Clarification: mass times velocity equals momentum verses foot pounds energy or slower and heavier vs. light and fast as some like to put it.

Don

 

[Semisane]

I prefer whompability.

:v It's kinda like pornography - hard to define, but you know it when you see it.

 

[Trench]

Since we're dealing with the high-end of pistol velocities with our MZ's, I'd tend to go with the importance of the momentum of the ball to be able to crush a wound from one side of an animal to the other facilitating loss of blood pressure. You need a pretty big temporary cavity to compress the spine sufficiently to cause the animal to drop on the spot and I don't think PRB's can do that on a normal basis. At least not with the loads I hunt with.
You don't hear a lot of stories of animals buckling from a PRB like you might see with your modern cartridges. I put a .490 PRB right through the spine of a buck in 2006 at 40 yds and the darn thing didn't even buckle from that. Sure, it was half parylized, but it didn't just fall down.
So, put me down for momentum!

 

[BrownBear]

I'd be embarrassed to admit how many deer I've taken over the years with handguns. But call it 25 years of exclusive handgun hunting with most years a 5 deer limit, some years 7 and more recently 3. Limits most years, so you can do the math.

I sperimented lots with expanding and hard cast, small calibers and large.

The comparison with handguns doesn't stretch very far in my experience, in spite of the similarities in velocities and bullet weights based on my recent years taking deer with PRB in muzzeloaders and helping dress others taken with all-lead conicals. If there's any basis for comparison between MLs and handguns, it starts vaguely with conicals in MLs.

The three big differences and flaws with the comparison are the larger surface area of RBs, the soft lead, and the miniscule sectional density.

It's a whomping BIG handgun that shoots a 50 cal bullet, and none shoot pure lead. Even the jacketed soft points and hollow points have that big long jacketed shank holding things together for more penetration. And as that big round pure lead ball starts to expand, it develops a sectional density somewhere between a frisby and a pizza.

In short, a 240 grain hard cast 44 cal (.429) pistol bullet will penetrate a whole bunch further than a pure lead PRB of the same weight at the same velocity. Switch to a harder alloy ball and the comparison improves. Switch to a conical and it gets closer. Switch to a hard lead conical from a ML, and then you're in the realm.

A pure lead conical will behave more like a jacketed soft point or HP from a handgun in terms of wound channel, expansion and penetration, but with a larger inititial striking surface. A hard lead conical from a ML is going to behave just like a hard cast from a handgun, except for the larger meplat, and is likely to whistle on through a deer, killing well but with a limited wound channel.

Based on fingering my way along lots of handgun wound channels and a growing number from MLs, we're dealing with apples and oranges until we start matching alloys, diameters and sectional density.

 

[longcruise]

And, don't forget the concept of terminal sectional density. In other words, the shape of the projectile after it strikes the animal and deforms to the extent that it will.

IOW, a fast moving prb will have that pizza sectional density which will somewhat retard penetration but then at the same time, velocity is upholding it's penetration. The prb at a much slower velocity will not deform as much and stay more round giving it a better (than the pizza) sectional density and therefore penetration even though the velocity is lower.

I've seen too many deer well penetrated and killed by .50 and .54 caliber balls with energy levels under, and sometimes way under, 500 ft lbs. to believe that it's about energy. IMO, its all about momentum and diameter of the ball.

 

[Stumpkiller]

Opening a can of worms here I know but when I was comparing momentum of my BP derringer loads to modern cartridge loads I was surprised by how well the BP loads compared. So what do you guys buy into as far as whats more important, muzzle energy or bullet momentum?

Don

First and foremost it has to go about where I aim it. Thereafter, I want an enterance hole and an exit hole. Any energy after that is wasted on trees and such.

The bonus of muzzle velocity can be nice in that it may lengthen your point-blank range; thereby giving you better chances of a good hit. But that can be compensated for by plenty of practice at varying ranges so you know your trajectory and the rifle or gun's peculiarities. Low velocity can also be accomidated by placing yourself closer to the target (most often useful in hunting situations as range officers sometimes frown on this).

Sometimes it is the challange that makes the sport. :wink:

 

[BrownBear]

I've seen too many deer well penetrated and killed by .50 and .54 caliber balls with energy levels under, and sometimes way under, 500 ft lbs. to believe that it's about energy. IMO, its all about momentum and diameter of the ball.

Agreed! Same experience here. That's why I like whompability rather than momentum or fpe.

 

[rkite]

A round ball takes a plug of skin out which leaves a very good blood trail. The problem is I have never needed to track a deer after shooting with my .54. I have had deer go much further with my 30-30. The round ball is one homogeneous piece of lead and does not fragment or loose weight, it just keeps driving straight in and penetrating regardless of the low kinetic energy.

 

[Zoar]

I'll take my disrespected 'ole 54 cal lead Round Ball over 110 grains of 3F nasty assed black powder with them "useless" iron sites out hunting "just about" any game in North America. Ka-Whomp. That is spelled Whompability! I believe. :grin:

Ballistics such as---".530 ball + 110 grains FFg = 1931 FPS = 1905 ft.lbs" ... Thus, with 3F increase figures by a safe 10%... but that only tells some of the story not all; what it does to animals is the story. :thumbsup:

I hear the hardened and sectional density argument, really I do. That is why I sometimes shoot flat meplat 435 grainer hardened lead cast bullets in my double 50-90 (brass cartridge gun) or 535 grainer round nosed Woodleighs delivering over 4,500 POUNDS of energy (ow, that'll leave a mark)... Yet I have been amazed by the size of critters taken down by a big Round Ball and the right amount of black powder... like anything in life you do have to hit them right... if you hit them wrong even if you are shooting a 500 smith and wesson with the heaviest, hardest bullet the animal will get away or worse come get you. I also agree with the post that said alot of the modern fad for these super bullets can be overkill. Period. The so called "added penetration" they assure actually means what goes into stumps, trees, dirt, etc., and is a total waste and might even be a cause for danger to the things it hits after it goes through the animal. I have a buddy who shoots MOOSE and BEAR in Canada with highly admirable regularity with Round Ball and a Muzzleloader... Yes, he hardens his RB's that he uses on Moose and Bear. :grin:

So, muzzle energey verses momentum---I guess I have to say both but the whole argument is not in either. The proof is in the results.

 

[longcruise]

Agreed! Same experience here. That's why I like whompability rather than momentum or fpe.

You should come up with a "whompability" formula. Hmmm. how about

Whompability = ball dia * (velocity/ball wt.) / barometric pressure * (price of gas/cost of lic)

 

[BrownBear]

Agreed! Same experience here. That's why I like whompability rather than momentum or fpe.

You should come up with a "whompability" formula. Hmmm. how about

Whompability = ball dia * (velocity/ball wt.) / barometric pressure * (price of gas/cost of lic)

I'll go for that formula. It makes just as much bull-istic sense as the ones I've seen for energy and momentum! :thumbsup:

 

[kevthebassman]

Paper ballistics amount to a hill of beans when talking roundball killing power. Put a .54 caliber roundball in the boiler room of any deer-sized game animal under 150 yards and it isn't gonna live to write home about it. All the talk of "knockdown power" is absurd, and the notion that the newest whiz-bang, $50 per 20 rounds cartridge can make a game animal "more dead" than the tried and true roundball is equally stupid.

There is no substitute for knowing your gun, getting close, picking your shot, and following through. If you can do those things well with a centerfire, you're likely to be just as successful with a roundball gun, plus you'll have the added satisfaction of a more challenging hunt, which I think is key.

If you're a slob of a hunter with a centerfire, (the "texas heart shot, it's brown it's down" crowd) you'll be a nightmare with a flinter in your hands, and you probably ought to pack it in and take up horseshoes or something. You surely shouldn't be taking shots at live game.

I myself derive little pleasure from the actual death of the animal. The challenge of the hunt and the romance of the traditional arms is where I find satisfaction. Though I must admit that a steaming hot bowl of venison stew is nothing to scoff at.

 

[tg]

"Paper ballistics amount to a hill of beans when talking roundball killing power"

I would second that notion I have taken deer with .40/.45/.50/.54/.58 and .62 PRB at ranges from about point blank out to 85-90 yds basical poking a hole in the vitals most deer went a ways and dropped some dropped within a few steps, no real pattern though I could say the same about a .308 from up close out to 300 yds in another life, each shot/animal is unique poke a hole in the right spot with any of the above and the animal will go down how soon will likely be determined by chance rather than having the ball be a bit larger than than one of the others(.40 droped a deer in its tracks at 30 yds/ pretty much the same shot with .58 and the deer ran 30 yds and piled up), there is a lot of variability(is that a word?) in that "kill zone" from one shot to the next that may at a glance seem to be identical, well enough rambling just put the ball in the zone be it a big ball or little ball and try to be realistic about the range for the size of ball due to the obvious energy issue, use a powder charge that does more than roll the ball out of the barrel, yet no need to get a bruised shoulder, and leave the mathematics for the guys at NASA for calculating trajectory of space craft or incomming catostrophic event heavenly bodies... wow how about that one Cooner does it qualify as a tirade?

 

[SimonKenton]

John "Pondoro" Taylor created the famous Knock Out Table for African cartridges. Note that the velocity of the projectile has less value than frontal area, sectional density and velocity in about that order.

Karamojo Bell slew hundres of elephants with a 7mm. Mauser and the old 175 grain round nosed solids.

PLACEMENT, PLACEMENT, PLACEMENT combined with reasonable mass and velocity. :thumbsup:

-Ray

 

[tg]

"PLACEMENT, PLACEMENT, PLACEMENT combined with reasonable mass and velocity'

absolutely Ray, and ya can't do it with a calculator......

 

[Zonie]

An old formula I've seen for years is basically the diameter of the projectile times the weight times the velocity.

While this doesn't give a number in foot pounds or newtons or ergs it does paint a pretty good picture of what the 'kill' factor of a bullet/ball is.

IMO, it takes all of the important things (except placement) into account.

 

[paulvallandigham]

Jim Refers to the " Killing Power " formula. Its Velocity times Ball, or bullet, weight, times Caliber, divided by 100. The "KP"number given is only relevant as a COMPARISON numeral, to use in comparing one given load or caliber to another.

As Jim indicates, it takes into consideration all the relevant issues excepting shot placement on the animal. But, then, none of the other " formulas" take shot placement into account, either. :hmm: :thumbsup:

The KP formula can be very useful for hunters trying to decide what the relative merits will be in using a PRB vs. a conical bullet in their gun.

One other thing the formula cannot take into account is what BrownBear mentions, and that is Lead Hhardness. A hard alloy lead ball is going to penetrate further, at higher velocities, than a soft lead ball at that same velocity.

At slow velocities, the soft lead ball may just penetrate as deeply as does the Hard alloy lead ball. The hard lead ball will weigh less than the soft lead, but the soft lead will expand some even at slower velocities. Weigh, or " Mass ", is what allows any projectile to penetrate flesh and bones, but these can be counteracted by designing a projectile that deforms on impact, creating a greater frontal area to push through the flesh and bones. Hard alloys tend to deform very little, as a general rule. :hatsoff: