Dr. Mann's book and some comments thereon

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  • Last Post 27 April 2015
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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billglaze posted this 27 April 2015

As closely as I can tell, throating seems to be one of the important parameters of cast bullet shooting. Probably with jb's also. I well recall when P.J. Wright, a riflesmith of some note, was building my over-the-course rifle in .308, he remarked, as we were coming up with what I wanted, “Lets see, as I remember, you use Sierra 168 Matchkings, don't you?” I answered in the affirmative, and he said: I believe we'll use one of Boots Obermeyer's barrels, or, if he can't deliver in a hurry, we'll use Krieger". Just like with a race engine, first comes the plan. He knew exactly how he wanted to throat the barrel. Same thing when he built my 1,000 yd. rifle. Both rifles were supremely accurate. Point of this diatribe? Seems to me there is a lot to this throating business; also, seems as if a lot of the good cast bullet groupers are using special throating. Exactly what makes it special has eluded me. 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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mtngun posted this 20 April 2015

gnoahhh wrote: I would imagine such things as proper throats and such were accurately addressed. But did Niedner and Pope know what a “proper throat” for cast bullets is?   Do we know even today?

Most gunsmiths simply follow SAAMI specs unless the customers requests a particular throat.   The SAAMI spec for most BP era cartridges is throat-less.

The fact that Mann never discusses throats, let alone that he never conducted experiments with throats, suggests that he was not aware of their importance.  

I don't recall Harry Pope discussing throats, either.   

I found this drawing of a Niedner 32-40 throat on http://www.doublegunshop.coms/ubbthreads.php?ubb=showflat&Number=319127>another forum.   It contradicts itself saying the “gentle leade” is 0.050” long.  Well if it is only 0.050” long then it is not gentle !

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gnoahhh posted this 20 April 2015

As an anecdotal aside, while re-reading “Yours Truly, Harvey Donaldson” this weekend, I noticed a passage where he stated that Dr. Mann was a terrible rifle shot and had to get other guys to do his test shooting (that didn't involve the use of the Mann V rest, which he supposedly invented to overcome his lack of rifle skills). Niedner and Pope did most if not all of the machine work he prescribed, so I would imagine such things as proper throats and such were accurately addressed.

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mtngun posted this 20 April 2015

I quite enjoyed Mann's book.

Re: inaccuracy due to bullet wobble.   Cast bullets (and even jacketed bullets) will always be imperfect but a slower twist reduces the wobble.   

Re: bore diameter bullets.   Here is my theory -- and it gets to something that Mann overlooked, the throat.  Mann's book never mentioned what kind of throat he had, but one assumes that, in the beginning of the book when he is shooting BP cartridges,  his chambers would have been throat-less as was (and still is) typical for BP cartridges.   In a throat-less chamber, it's not surprising that Mann got better accuracy by seating bore diameter bullets beyond the abrupt throat.  

Towards the end of the book Mann switched to smokeless cartridges like the 30-40 Krag.  The Krag has a decent throat and Mann then was able to get good results with conventional bullets.    :fire

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RicinYakima posted this 20 April 2015

L.E. (Sam) Wilson did the same type of experiment in the 1930's with jacketed bullets. The “Best” vs. the “worse” did not shoot either smaller or larger groups at 200 yards. Others have also tried this test, many posted on the internet; all failures. The magic happens when the malleable bullet expands when the powder pressure is present. I don't know what it is, and nobody else does either in any test I have seen.

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billglaze posted this 19 April 2015

Another of the experiments Mann conducted to prove or disprove his “unbalanced bullet” theory is interesting. He had a machine constructed to spin bullets at a very high rpm. It incorporated a rotating tube in a vertical position, such that, while spinning at a high rate, contained a bullet. This tube was of such a diameter as to permit the bullet to easily slide thru it, and deposit the spinning bullet on a catch tray under the lower end of the hollow tube. The idea was to get the bullet spinning, then push it out of the tube, where it could spin rapidly like a child's top. Very seldom could he get one to spin; in fact, sometimes the bullet was far enough out of balance that it was impossible to get it to leave the tube. Occasionally, he would get one that actually spin like a top. And yet, at Camp Perry a friend pulling targets in the butts, during the 1000 yd. match, spotted a bullet deflected by (apparently) hitting the target frame, spinning on it's nose like a top. This was on the concrete floor of the pits. He picked it up and blistered his thumb and trigger finger. Hot!

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 18 April 2015

Tom, Another is Mattern's Handloading Ammunition, from about 1926. He was loading 1000's of rounds of ammo every year, before loading presses were invented, with hand tools. I don't know if it has been stolen and loaded onto the Internet or not, but print copies are available. The last of the classics is Naramore's Principles and Practices of Handloading Ammunition, from about 1957. Again, I don't know if it is on the Internet or not. So the above four books is an excellent survey of reloading from 1900 through 1970. However, Joe Brennen's Cast Bullets, for Beginner and Expert, 2nd Ed., 2007, is the best book on cast bullets from the last 30 years. It is free and updated on the LASC website. Ric

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Tom Acheson posted this 18 April 2015

Speaking of old books.....just found this in my pile of books “Complete Guide To Handloading” by Phillip B. Sharpe. Third edition, copyright 1949. Sharpe dedicates it to Harry M. Pope. If nothing else it is interesting to see what was happening in the handloading world at the time and what is described as “new” handloading tools that were just introduced.

Tom

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John Alexander posted this 18 April 2015 

      Nobody here has said that Mann's book was infallible.  There may be some TBF fundamentalists that believe the book came down off a mountain on clay tablets but we haven't heard from them.  It is like any other set of findings that in spite of best intentions may be influenced by the experimenter's previously held biases or misconceptions.  The most careful work may be proven wrong later and has been repeatedly in the history of science.

   It pays to be skeptical of anything said or written and use some critical thinking and experimentation to test it out.  Cast bullet shooters in general often don't often display this healthy skepticism and will swallow the conventional wisdom like a puppy swallows a poisoned hamburger.  Our reverence for a perfect 11 degree crown is a case in point that should have been put to rest 110 years ago when Mann showed it to be BS.  It is worthwhile to have a few Joe Brennan type skeptics around.

 Maybe the excessive reverence some of us show towards Mann's work is because we have so little published high quality experimentation going on and progress in shooting cast bullets seems to be at a crawl, if not stopped.

  John    

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joeb33050 posted this 18 April 2015

How about the ideas in Pg 177, “Mirage vs. Telescope” , Sept. 1904,or  Pg. 183, “Superiority of Bore Diameter Bullet Discussed” .
What we've got here is a difference of opinion.I like Frank, he did a lot of experimentation, spent a lot of money, shot a lot of shots, and exercised H. M. Do we believe that measuring twist with a tight patch on a cleaning rod gives incorrect estimates?Has Frank's twist measuring method caught on? Can an eye, a glass and a scale measure angles precisely?
Plank shooting?

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RicinYakima posted this 17 April 2015

But do you care, Ken?

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Ken Campbell Iowa posted this 17 April 2015

philosophy vs math ... oh crap ... i am not good in math and also don't know why ...

ken

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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.

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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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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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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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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

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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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

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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