Dr. Mann's book and some comments thereon

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Last Post 27 April 2015

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billglaze posted this 15 April 2015

Recently, while recuperating form the Flu, I took 4 days and re-read Mann's book about the Bullet's Flight. Interesting, and Pope's marginal comments were also revealing. Dr. Mann, after exhaustive testing, and record keeping, came to two basic reasons for inaccuracy: First, the bullet in the bore rotates around center-of-form, and second, when airborne it rotates around center-of-gravity, which seems to be two entirely different points in/of the bullet. Makes sense. He goes on to mention that he found that one in five shots was a “flyer". (Sound familiar?) He was able to mutilate bullets in such a manner as to control the direction of self-made “flyers” and predict where they would land, with respect to the major center of grouping. He also pinpointed wobble of the airborne bullet, and how much so, caused by several forces. This intentional inaccuracy was caused by both mutilating the base, and the point, (or forward portion) He also measured the base of bullets for other than 90 degree angle; he found that, out of 122 bullets recovered, 120 had a malformation of the bullet, caused either by the molds, by sizing, (even very carefully done, precision sizing) or by the rifle bore. Thusly, his conclusion seemed to be that the bullet hadn't much of a chance of precision impact. He also mentions that, when casting, the bullets cool from the outside inward. Logical. He also claims that the CG seldom conforms to the CF. Actually, the entire thing while well thought out and well supported by thorough research and documentation, was pretty discouraging. He never did come up with a “cure” for that one-in-five we all hate. I'm throwing this out for those folks who may be interested, and either not have the book, or didn't want to wade through it, or came up with different conclusions. Reading it was a bit tedious. Bill

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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TRKakaCatWhisperer posted this 16 April 2015

Bill - thanks! Good summary.
It would indeed be an interesting, if not lengthy, project to vary the mould designs to find the variables that could be influenced to get the convergence of CF and CG.

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RicinYakima posted this 16 April 2015

Bill,

Thanks for the post. I have three copies, a 1941 edition done by his daughter, a Wolfe reprint of the original and an annotated reprint of the one with Pope's notes. Both of the reprints are very poorly done, as the pictures are unusable for illustrations of what he was doing.

It answers 99% of the questions about accuracy, so I have quit commenting on those, as nobody other than yourself has ever said they took the time to work their way through his research. Congratulations!!

Best wishes, Ric

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Ken Campbell Iowa posted this 16 April 2015

i found a strange disconnect that as long as used lead bullets, he primarily used bore-riders ... i would have thought it would have occured to him that they would randomly slump upon firing .

ken

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RicinYakima posted this 16 April 2015

Mann was limited in two areas: the “common knowledge” of the day created by the Schuetzen shooters and his work was pre-gas check. Until his work, everyone knew that bullet deformation was from it melting (fusion) from the heat of the gunpowder burning and bullets stripped in the rifling if shoot too fast. I would surely loved to have read the last 5 years of his experiments, before it was all thrown away upon his death. I would suspect that he was looking at randomness of pressure deformation.

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John Alexander posted this 16 April 2015

If more serious CB shooters would read Mann’s book and think about it we would make more progress. Maybe a reread about once every five years – every year for us geezers who ain’t remembering so good.

Hard to argue that center of gravity (cg.) and center of form (cf) not being on the same axis can’t cause inaccuracy since it can be shown that it does by filing big notches in the base or meplat or drilling holes in the outside. You can even predict which direction they will fly by controlling their position when chambered (indexing.) Interestingly, if they are indexed the same they will shoot excellent groups but at a different zero.

However, I doubt that cg/gf is a problem for most of us. For starters a good machinist should be able to make a mold that is round (although I’m not sure that is necessary) and have all it’s surfaces concentric. With that “perfect” mold what could go wrong? Inconsistent density of the bullet from one side to another? I dump my new bullets on an insect screen gadget because I used to worry about that and wanted them to cool at the same rate not to be insulated by a towel on one side. It didn’t solve my problems.

The dreaded air voids are another possibility. Do you believe in them? I don’t anymore because in spite of turning down scores of bullets a couple of thousandths at a time and sawing off slices of dozens more, I have never seen an air void and I can’t think of a way to show that they exist. I know they have been observed, often in very large caliber bullets, but for the small bullets I cast and the way I cast them (which isn’t special) I can’t find any.

I don’t believe in fairies, so unless you have a faulty mold, non homogenous alloy, or air voids what would make an UNSIZED bullet have a cg/cf problem? Of course I am talking only theory here. If that doesn’t work, I have an argument based on performance but this post is already too long.

John

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joeb33050 posted this 16 April 2015

After years of trying to read and understand Mann's book, I've decided that it's gibberish. I don't know if it's an intentional joke, or just the product of a disordered mind. I particularly note the parts that tell us that mirage doesn't move the target, and the part showing how bullet bases expand as the barrel is shortened. Pictures of gibberish.It's gibberish.

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John Alexander posted this 16 April 2015

Always good to have the voice of reason and moderation Joe. That's what makes the forum worth visiting. You may have your BS detector turned up too high. I can agree that some of Mann's experiments, results, and conclusions or the lack thereof and the way he presented them wouldn't do well as a high school science project. Other things I couldn't see why he cared. But then that's the kind of things that basic science tries to find out about and that's a good thing. I have a whole list of things that I wish he had done differently and written more clearly about but not everything worthwhile is perfect. It is sometimes maddening to read -- “a bit tedious” as Bill politely put it.

But he did make hamburger out of some of the sacred cows of his day (some which have been resurrected by modern shooters) and there is never any shortage of such cows as raw material. And he did it while the rest of the serious shooters were nodding their heads sagely and agreeing with the conventional wisdom BS of the time. The need for a near perfect crown and the firm belief that muzzle blast on the departing bullet is a major factor in accuracy to name a couple without refreshing my memory by going back to the book.

As far as the bases of lead bullets expanding as the barrel is shortened I believe that experiment was replicated and published in the Am Rifleman a few decades ago when it was still a shooting magazine. As I remember a pistol barrel was shortened until there was none and the rear end of the bullets looked like the ones in Mann's book. I thought it was sort of interesting.

I wish we had a modern day Mann with the time and money as well as some training in the scientific method.

John

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billglaze posted this 16 April 2015

After reading through the book,, the major area I disagree with, was his conclusion on mirage. As an old desert rat, too many times have I ridden down a black asphalt road and seen the mirage boiling up. And, many times I have seen landscape projected into the atmosphere above the horizon; landscape that isn't even visible until topping a rise in the highway. The other major concern I have is that the barrels were not in any kind of a “natural” state, such as they would have been if mounted in a rifle. He did utilize his own method, feeling that his idea of putting large diameter “collars” on the barrels, and hanging an action off the breech end, would provide the most constant condition. Maybe so, maybe not. However, it was, at least, constant. I know of nobody, before or since, who has seen fit to systematically and in a detailed manner, research the problems, and has also seen fit to publish. I feel sure that the good Doctor knew he was making himself a very large and visible target.

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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billglaze posted this 16 April 2015

Oh, one other thing: His statement that the bullet casting “cools from the outside in” is scarcely a non-intuitive revelation. However, his conclusion that this situation causes “different densities” in the casting, thereby generating the difference between COF and COG if true, would make nearly impossible the casting of a homogenous bullet. Discouraging. I know of no other way to test this statement other than a (probably) expensive lab test, if such a thing is even possible. Until now, it remains his theory. To my knowledge, not proved or disproved, but it's not my area of expertise. Anybody else?

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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joeb33050 posted this 17 April 2015

THE BULLET’S FLIGHT

Mann’s book, “The Bullet’s Flight…” , is a Google book, free online. Search on “The Bullet’s Flight” .
            I have read, or tried to read, this book for something over forty years.
            A few years back I thought that perhaps I could write a clear interpretation of TBF, could write an understandable explanation.
            “The General Theory of Employment, Interest and Money” was written by John M. Keynes, and is incomprehensible to the layman and most economists. One indicator of BS emerging from the mouth or pen of a writer or speaker is his claim to have read and understood TGT.
Alvin Hanson’s “A Guide to Keynes” translates TGT into language that we can understand. I thought I might be Mann’s Hansen.
Alas, Keynes’ writing suffered from his genius, but Mann’s writing has no, (or little) fundamental contribution to be explained-there’s nothing there.
Since reference to and admiration of Mann’s work is commonplace, we-the noncomprehenders- assume that we are at fault, that we’re too stupid to understand Mann.
T’aint so, it’s mostly gibberish.
Now, we can easily access and read TBF on the net, so let’s take an example.
Go to page 338, “Determining Rifle Twist” , “Test 177” It’s not long, not hard to read. Can anyone explain this, tell me what he’s talking about? John?

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joeb33050 posted this 17 April 2015

billglaze wrote: After reading through the book,, the major area I disagree with, was his conclusion on mirage. As an old desert rat, too many times have I ridden down a black asphalt road and seen the mirage boiling up. And, many times I have seen landscape projected into the atmosphere above the horizon; landscape that isn't even visible until topping a rise in the highway. The other major concern I have is that the barrels were not in any kind of a “natural” state, such as they would have been if mounted in a rifle. He did utilize his own method, feeling that his idea of putting large diameter “collars” on the barrels, and hanging an action off the breech end, would provide the most constant condition. Maybe so, maybe not. However, it was, at least, constant. I know of nobody, before or since, who has seen fit to systematically and in a detailed manner, research the problems, and has also seen fit to publish. I feel sure that the good Doctor knew he was making himself a very large and visible target.

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John Alexander posted this 17 April 2015

joeb33050 wrote:

THE BULLET’S FLIGHT

Mann’s book, “The Bullet’s Flight…” , is a Google book, free online. Search on “The Bullet’s Flight” .

T’aint so, it’s mostly gibberish.

Now, we can easily access and read TBF on the net, so let’s take an example.

Go to page 338, “Determining Rifle Twist” , “Test 177” It’s not long, not hard to read. Can anyone explain this, tell me what he’s talking about? John?

Joe,

There is a lot in the book that didn’t interest me and some of the reporting was murky, but I thought his little experiment on determining rifling twist the hard way was interesting although of no “practical” application. I will agree that the Mann book could use a Hansen although much of it was perfectly clear to me (including this section.) I won’t try to be a Hansen even for this section but maybe I can explain the test, as I understood it.

By shooting a bullet with a wedge shaped nose is it possible to see which way the wedge (bullet) is aligned (where it is in its rotation) as it goes through a paper target. For example, if the wedge edge was aligned vertically as it passed the muzzle it should be aligned vertically again at a distance from the muzzle equal to it’s twist as we define it – ten inches in this case (as well as at 5 inches). Given how twist was controlled while rifling a bore in those days the factory twist should be pretty close.

When Mann found that his bullet had rotated a bit less than the actual factory twist between a series of screens ten inches apart starting at 6 feet (second row of prints.) He explained it by claiming that muzzle blast had caused the linear velocity of the bullet to increase for the first 25 diameters from the muzzle but muzzle blast shouldn’t speed up the rotational velocity. Therefore at 6 feet the bullet was traveling a little quicker between screens and it hadn’t rotated quite one full turn.

For folks who doubted that bullets speed up once out of the muzzle he then repeated the test with the screens starting at 20 and 30 feet where everybody can agree that air friction should have slowed the linear velocity but not the rotational velocity. Although it is hard to see in the book (fourth and fifty row of prints) his measurements showed, as expected, that the bullets rotated a little more between screens than the twist would indicate while going 10 inches because it took longer to get there at the lower linear velocity.

I don’t know if my explanation is any better than Mann’s reporting or not. But to me it was a very neat and tidy test. (His telling us more than we needed to know about fritzing around to get the spacing exact did muddy the water a bit.) But I don’t see any gibberish here at all. I do think his claiming this is a better way to measure twist than a tight patch pushed through is using a bad patch test as a straw man. I have found that finding twist with a tight patch is a easily repeatable test and corresponds very well in cut or hammer forged barrels which should be as advertised. With button rifled bores – sometime a bit off.

John

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RicinYakima posted this 17 April 2015

Joe, Mann's test #177 is physical verification of the actual spin rate of a bullet fired from a barrel. The wedge shaped nose is shot through five paper targets placed 9 inches apart in the first firing, then 10 inches apart in the second. By measuring the angles of the blunt nose marks, he can calculate the rate of the bullet turning in air. Just because one person does not understand what is written, do not assume that others can not understand. The only place one could be lead astray is when he writes “examined with a steel scale” if you did not realize that he was measuring the angles of nose movement from vertical as the bullet spun through the air.

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John Alexander posted this 17 April 2015

billglaze wrote: Oh, one other thing: His statement that the bullet casting “cools from the outside in” is scarcely a non-intuitive revelation. However, his conclusion that this situation causes “different densities” in the casting, thereby generating the difference between COF and COG if true, would make nearly impossible the casting of a homogenous bullet. Discouraging. I know of no other way to test this statement other than a (probably) expensive lab test, if such a thing is even possible. Until now, it remains his theory. To my knowledge, not proved or disproved, but it's not my area of expertise. Anybody else? This claim that differential cooling could cause a change in density leading to the CG/CF problem seems like a thin theory to me. Cast iron, steel, and aluminum conduct heat very well and I doubt that the temperature is much different between spots maybe .3” apart in the interior of the mold. Cooling after the bullet is dropped should be fairly uniform if the bullet is dropped on a fiberglass or other non conducting mesh which is easy to do. Dropping the bullets on a relativity insulating material like a towel might be something to look into. Merrill Martin thought so.

If there is anything to this theory it could be easily confirmed, at least qualitatively, if hardness corresponds to density and a person has access to a micro hardness testing device. How about it some of you material scientists out there?

John

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joeb33050 posted this 17 April 2015

Yeah, it must be me. I thought that a bullet's rotational velocity was independent of it's linear velocity, at least through 30 feet. I thought that a 10” twist turned the bullet one turn = 360 degrees every 10” of travel, at 1000 fps and 2000 fps and 3000 fps and... Whether the muzzle blast accelerated the bullet or not. It must be me.

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John Alexander posted this 17 April 2015

joeb33050 wrote: I thought that a bullet's rotational velocity was independent of it's linear velocity, at least through 30 feet. You are right at least it is claimed that rotational and linear velocity ARE independent starting as soon as the bullet clears the muzzle (linear velocity slows because of air friction, rotational velocity not so much.) That's why Mann saw what he did on the screens.

Let's look at a longer range. A bullet is shot out of a 10” twist barrel at 2,000 fps. Near the muzzle the linear velocity wouldn't have changed much so it would rotate approximately once every ten inches just like when inside the bore.

Linear velocity slows to 1,000 fps at some range. At that longer range if it is still rotating at the same rate (RPM) and going only half as fast as it was at the muzzle so it can go only half as far during one rotation or 5 inches.

Mann's examples are only different in that both linear velocity changes and degree changes on paper are smaller.

John

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Ken Campbell Iowa posted this 17 April 2015

brute force .

mann used brute force to process questions regarding accuracy .

i once for fun wrote a computer program to calculate a desired set out of all possible combinations of 100 change gears for my gear shaper . when my pc was still running the next morning i got bored and shut it off . besides it takes me about a minute to select the correct set in my mind ....

perhaps dr. mann was fascinated by PROCESS ... not all bad; my coyote trail hounds seemed to enjoy the PROCESS ...

ken

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billglaze posted this 17 April 2015

Ken: A friend of mine on the airline was also a sail designer. Designed them for competition boats all over the world. Highly technical and mathematical job; much like designing a wing with infinitely changing airfoils. He had established a design and transferred it to a computer analog, and from there to math formulas. He had a state-of-the-art p.c. at home, and it was going to take something like over 17 hours to grind out the configurations. A friend of his at Douglas Aircraft in Long Beach got him into the engineering bldg. late one night, and he fed the programming into the Douglas mainframe. The answer came out in .7 second! Thought there was a mistake; tried it again. Same thing. I never found out what the computer was; sounds like it was maybe advanced over a Cray. Bill

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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RicinYakima posted this 17 April 2015

I took a very interesting class from the department head of St. Martins college on teaching vocational education to adults. There are two extremes of learners; one is the mathematician who only believes in numbers and the philosopher who only believes in ideas. Franklin Mann was much more to the philosopher end of the scale. All of his math is simple and is only used to support his conclusions.