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Mathematical Challenge re: CE 399 - Bob Prudhomme - 08-03-2014
Here is a challenge for those members with mathematical or geometrical talents. Using this photo of CE 399,
or any other photo of CE 399, can anyone determine how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Thanks in advance.
Mathematical Challenge re: CE 399 - David Josephs - 08-03-2014
Quote:how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Hi Bob..
Isn't a full rotation defined by the barrel itself... the grooves in the barrel complete 4 rotations,or something like that? or is it a 4 groove barrel with an unknown number of rotations?
The distance between these complete rotations within the barrel will give you your distance since it does not matter whether the bullet falls out of the barrel or is shot out,
.... the bullet wouldn't rotate at all without those grooves I imagine...
So I looked up rifling and found this on wiki: do we know the Twist Rate of the MC?
DJ
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as "1 turn in 10 inches" (1:10 inches), or "1 turn in 254 mm" (1:254 mm). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.
http://en.wikipedia.org/wiki/Rifling
Mathematical Challenge re: CE 399 - Bob Prudhomme - 08-03-2014
David Josephs Wrote:Quote:how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Hi Bob..
Isn't a full rotation defined by the barrel itself... the grooves in the barrel complete 4 rotations,or something like that? or is it a 4 groove barrel with an unknown number of rotations?
The distance between these complete rotations within the barrel will give you your distance since it does not matter whether the bullet falls out of the barrel or is shot out,
.... the bullet wouldn't rotate at all without those grooves I imagine...
So I looked up rifling and found this on wiki: do we know the Twist Rate of the MC?
DJ
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as "1 turn in 10 inches" (1:10 inches), or "1 turn in 254 mm" (1:254 mm). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.
http://en.wikipedia.org/wiki/Rifling
Yes, David, those definitions are correct. A rifle barrel that has rifling grooves with a 1:10 rate of twist means that the bullet will make one complete rotation in the space of 10 inches of the barrel's length. It will leave the distinctive rifling marks, as seen on CE 399.
However, different rifles have differing rates of twist in their riflings, as well as the "lands and grooves" being of varying widths. It is not uncommon, in sporting rifles, to see rates of twist vary from 1:7 to 1:12. Naturally, the tighter twist will leave much tighter rifling marks on a bullet. As CE 399 is the evidence presented by the WC, I am attempting to establish the rate of twist of the barrel it was fired from to see if it matches the known rifling specs for Carcano rifles.
P.S. Yes, we know the rate of twist for Carcano barrels. It will vary, in a short barrel, depending on which rifle it was. See the final post in my thread "Request for Help to ID Rifles" and you will likely understand why I am so interested in determining the rate of twist of the riflings in the barrel that fired CE 399.
Mathematical Challenge re: CE 399 - David Josephs - 08-03-2014
Bob Prudhomme Wrote:David Josephs Wrote:Quote:how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Hi Bob..
Isn't a full rotation defined by the barrel itself... the grooves in the barrel complete 4 rotations,or something like that? or is it a 4 groove barrel with an unknown number of rotations?
The distance between these complete rotations within the barrel will give you your distance since it does not matter whether the bullet falls out of the barrel or is shot out,
.... the bullet wouldn't rotate at all without those grooves I imagine...
So I looked up rifling and found this on wiki: do we know the Twist Rate of the MC?
DJ
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as "1 turn in 10 inches" (1:10 inches), or "1 turn in 254 mm" (1:254 mm). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.
http://en.wikipedia.org/wiki/Rifling
Yes, David, those definitions are correct. A rifle barrel that has rifling grooves with a 1:10 rate of twist means that the bullet will make one complete rotation in the space of 10 inches of the barrel's length. It will leave the distinctive rifling marks, as seen on CE 399.
However, different rifles have differing rates of twist in their riflings, as well as the "lands and grooves" being of varying widths. It is not uncommon, in sporting rifles, to see rates of twist vary from 1:7 to 1:12. Naturally, the tighter twist will leave much tighter rifling marks on a bullet. As CE 399 is the evidence presented by the WC, I am attempting to establish the rate of twist of the barrel it was fired from to see if it matches the known rifling specs for Carcano rifles.
It is my opinion that CE399 was fired from the MC planted on the 6th floor well before-hand and was given to Elmer Todd by Chief Rowley...
Bob... how can you tell from the bullet what the twist rate is... this is the exhibit that supposedly shows CE399 and a bullet fired from the C2766 are the same...
http://aarclibrary.org/publib/jfk/wc/wcvols/wh17/html/WH_Vol17_0142a.htm
yet unless one knows the twist rate of the barrel, i assume there is no way to reverse engineer that info from the bullet... ??
Mathematical Challenge re: CE 399 - Bob Prudhomme - 08-03-2014
David Josephs Wrote:Bob Prudhomme Wrote:David Josephs Wrote:Quote:how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Hi Bob..
Isn't a full rotation defined by the barrel itself... the grooves in the barrel complete 4 rotations,or something like that? or is it a 4 groove barrel with an unknown number of rotations?
The distance between these complete rotations within the barrel will give you your distance since it does not matter whether the bullet falls out of the barrel or is shot out,
.... the bullet wouldn't rotate at all without those grooves I imagine...
So I looked up rifling and found this on wiki: do we know the Twist Rate of the MC?
DJ
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
Rifling is often described by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as "1 turn in 10 inches" (1:10 inches), or "1 turn in 254 mm" (1:254 mm). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.
http://en.wikipedia.org/wiki/Rifling
Yes, David, those definitions are correct. A rifle barrel that has rifling grooves with a 1:10 rate of twist means that the bullet will make one complete rotation in the space of 10 inches of the barrel's length. It will leave the distinctive rifling marks, as seen on CE 399.
However, different rifles have differing rates of twist in their riflings, as well as the "lands and grooves" being of varying widths. It is not uncommon, in sporting rifles, to see rates of twist vary from 1:7 to 1:12. Naturally, the tighter twist will leave much tighter rifling marks on a bullet. As CE 399 is the evidence presented by the WC, I am attempting to establish the rate of twist of the barrel it was fired from to see if it matches the known rifling specs for Carcano rifles.
It is my opinion that CE399 was fired from the MC planted on the 6th floor well before-hand and was given to Elmer Todd by Chief Rowley...
Bob... how can you tell from the bullet what the twist rate is... this is the exhibit that supposedly shows CE399 and a bullet fired from the C2766 are the same...
http://aarclibrary.org/publib/jfk/wc/wcvols/wh17/html/WH_Vol17_0142a.htm
yet unless one knows the twist rate of the barrel, i assume there is no way to reverse engineer that info from the bullet... ??
David
The riflings will leave an exact impression on the bullet of the last part of the inside of the barrel (the muzzle) to contact the bullet. The copper jacket of the bullet is quite malleable, and the riflings will imprint onto the bullet jacket just as if they were clay. If the rate of twist at the muzzle of the rifle is 1:8, an imprint, corresponding to a 1:8 rate of twist, will be left on the bullet.
I don't doubt that CE 399 was fired from the rifle found on the 6th floor of the TSBD. That is not at issue here. What I am trying to determine is the rate of twist of the rifle found on the 6th floor.
Think about this really hard for a second, Dave, and don't make assumptions without the knowledge to back them up. Why would we need to know the rate of twist of the barrel's rifling? We do not even need to know the length of the bullet in the photo we are told is CE 399. All we need is to measure the diameter of the bullet in the photo and compare that to the known diameter of a 6.5 Carcano bullet, which is .268". This will give us a ratio that we can use to establish a 1 inch length on the bullet. In that 1 inch, we need to determine how much of the circumference of the bullet the rifling mark has covered. This is where I have problems and why I am asking help from more experienced members. Once we have that figure, either as a percentage of the circumference or as a fraction of .842" (circumference of a .268" diameter bullet), it should be a simple matter to determine the rate of twist of the rifle.
Mathematical Challenge re: CE 399 - David Josephs - 08-03-2014
Quote:I don't doubt that CE 399 was fired from the rifle found on the 6th floor of the TSBD. That is not at issue here. What I am trying to determine is the rate of twist of the rifle found on the 6th floor.
Sorry for sounding stupid Bob... in one sentence you know that ce399 came from C2766
in the next you are trying to determine the rate of twist of C2766, the rifle found on the floor... ?? Wouldn't that be a function of what we see on CE399?
Or are you saying C2766 was not the rifle found on the 6th floor.
Let me try some examples to try and understand you regarding the marks on CE399, which can be measured
The barrel of a 91/38 FC is 53.8 cm or 28.1811 inches.
http://kwk.us/twist.html is a twist rate calculator I found online - I used 2.8 inch length, .268 diameter, 2000fps? and 8.9 bullet SG and got a 3.6 inch twist rate....
Does this mean that the bullet spin 28.181" / 3.6" times before it left the muzzle ?
Unless there is a manufacturer's spec on the twist rate i seems to me we have to have a bullet fired from the rifle to determine that rate
DJ
[TABLE="align: center"]
[TR]
[TD="align: left"]nputs[/TD]
[TD="align: center"]outputs[/TD]
[/TR]
[TR]
[TD="align: right"]bullet length[/TD]
[TD] in[/TD]
[TD="align: center"]twist in[/TD]
[/TR]
[TR]
[TD="align: right"]bullet diameter[/TD]
[TD] in[/TD]
[/TR]
[TR]
[TD="align: right"]muzzle velocity[/TD]
[TD] fps[/TD]
[TD="align: center"]errors[/TD]
[/TR]
[TR]
[TD="align: right"]bullet SG[/TD]
[TD][/TD]
[TD="align: center"][/TD]
[/TR]
[TR]
[TD]bullet SG values:[/TD]
[TD="align: center"]11.3 lead
8.9 copper
8.5 brass
7.8 steel
[/TD]
[/TR]
[/TABLE]
[ATTACH=CONFIG]5764[/ATTACH]
Mathematical Challenge re: CE 399 - Bob Prudhomme - 09-03-2014
David
You have a habit of taking something very simple and complicating it to the point of ridiculousness. You may be doing this unwittingly so I won't hold it against you.
Yes, we are assuming CE 399 was fired from C2766. Even the FBI would not be so stupid as to try to plant a bullet from a different rifle.
This is so simple, even my wife caught on to what I am looking for.
If the rifling mark made it 1/4 the way around the bullet in a 1 inch lengthwise space of the bullet, it is likely that, if the bullet travelled 4 inches down the barrel, the bullet would make one complete revolution of spin. We would describe the rate of twist as 1:4, or one complete revolution of spin in 4 inches.
However, we do not know the length of a 6.5mm bullet as made by the Western Cartridge Co., although it may be similarly close to the Italian military bullet, which measured 1.238 inches in length. It will require some degree of skill to estimate the length of the bullet in the photo or, on the other hand, it may not be necessary, as the number we come up with will be expressed as a ratio. Even more difficult is estimating how far around the circumference of the bullet the rifling mark seen in the photo has travelled.
P.S. Read the thread I directed you to and you will understand what I am trying to do here. There is some doubt that all Carcano rifles made from 1938 on, which reputedly all had standard twist rifling, actually did have standard twist rifling and were not, in actuality, merely made from cut down M91 long rifle barrels cut with progressive twist rifling, due to manufacturing strains placed on Italian armes makers as the war turned against Italy. If it turned out we could prove C2766 was one of these, the resulting loss of accuracy would completely disqualify it as being capable of the JFK assassination shooting.
Mathematical Challenge re: CE 399 - David Josephs - 09-03-2014
Bob Prudhomme Wrote:Here is a challenge for those members with mathematical or geometrical talents. Using this photo of CE 399,
or any other photo of CE 399, can anyone determine how many inches this bullet would have to travel, in the barrel it was fired from, in order for it to make one complete revolution?
Thanks in advance.
Quote:Once we have that figure, either as a percentage of the circumference or as a fraction of .842" (circumference of a .268" diameter bullet), it should be a simple matter to determine the rate of twist of the rifle.
Y'know Bob, if it was "simple" you'd do it, right? I did not mean to make it more complicated, I simply did not understand the mechanics of a bullet moving thru a barrel.
Mr. EISENBERG - Yes; for the record, these cartridges were found on the sixth. floor of the School Book Depository Building. They were found near the south east corner window--that is, the easternmost window on the southern face of the sixth floor of that building.
Mr. Frazier, are these cartridge cases which have just been admitted into evidence the same type of cartridge-- from the same type of cartridge as you just examined, Commission Exhibit No. 141?
Mr. FRAZIER - Yes; they are.
Mr. EISENBERG - That is, 6.5 mm. Mannlicher-Carcano, manufactured by the Western Cartridge Co.?
Mr. FRAZIER - Yes, sir.
Mr. EISENBERG - You gave the weight of the bullet which is found in this type of cartridge. Could you give us a description of the contour of the bullet, and its length?
Mr. FRAZIER - The bullet has parallel sides, with a round nose, is fully jacketed with a copper-alloy coating or metal jacket on the outside of a lead core. Its diameter is 6.65 millimeters. The length--possibly it would be better to put it in inches rather than millimeters The diameter is .267 inches, and a length of 1.185, or approximately 1.2 inches.
So these are Centimeters
[ATTACH=CONFIG]5769[/ATTACH] [ATTACH=CONFIG]5768[/ATTACH]
Each of these ruler marks is 1/10th of a centimeter...
the length of the groove is about 21 cms or .826772 inches...
so it appears to have rotated .25 cms = 0.0984252 inches of turn over .826772 inches of bullet or an 8.4:1 ratio of twist
Mathematical Challenge re: CE 399 - Bob Prudhomme - 09-03-2014
Dave
Right off the bat, Frazier couldn't do math to save his life. I've proven this several times. 6.65 mm does not equal .267", 6.65 mm = .2618". A 6.5 mm Carcano bullet is actually 6.8 mm in diameter, if made to the Italian military specs. You may just have unwittingly uncovered the proof I have been seeking for so long that proves the Western Cartridge Co. 6.5mm Carcano ammunition was loaded with hopelessly undersized bullets that would have destroyed the accuracy of any shot made from that rifle.
Mathematical Challenge re: CE 399 - David Josephs - 09-03-2014
Bob Prudhomme Wrote:Dave
Right off the bat, Frazier couldn't do math to save his life. I've proven this several times. 6.65 mm does not equal .267", 6.65 mm = .2618". A 6.5 mm Carcano bullet is actually 6.8 mm in diameter, if made to the Italian military specs. You may just have unwittingly uncovered the proof I have been seeking for so long that proves the Western Cartridge Co. 6.5mm Carcano ammunition was loaded with hopelessly undersized bullets that would have destroyed the accuracy of any shot made from that rifle.
Uh, ok. hope I helped...
found this interesting...
Take care
DJ
Mr. MCDONALD. Did you compare the FBI test bullets with your own test bullets that you recently fired out of 139?
Mr. BATES. Yes, we also made a microscopic comparison of that.
Mr. MCDONALD. And what did the comparison show?
Mr. BATES. The results of this examination indicated that we could not determine whether the FBI test bullets were, in fact, fired from the rifle, CE-139
Mr. MCDONALD. Would you have expected that result considering the number of times that CE-139 has been fired over the years?
Mr. BATES. Yes, we would have.
Mr. BATES. The panel, including myself, conducted comparative microscopic examinations of CE-399 against both of the FBI test bullets, CE-572.
Mr. MCDONALD. What findings did you make?
Mr. BATES. As a result of our comparative microscopic examinations, it is our opinion that the bullet, CE-399, was fired through
the same firearm barrel that fired the FBI tests, CE-572.
Mr. MCDONALD. Can you determine the caliber of a rifle merely by looking at it?
Mr. LUTZ. No, you cannot, because many times the differences in caliber is a few thousandths of an inch. The difference between a 6.5-millimeter Carcano bullet, or the muzzle, the barrel itself, the inside diameter, and the difference between it and the 7.65 German Mauser is only a few thousandths of an inch, 40-some thousandths of an inch difference. We are speaking of .265 inches in diameter for the 6.5 Mannlicher-Carcano bore diameter and we are speaking of .313 inches of diameter for the Argentine Mauser made in Germany.
Frazier converted wrong... but he does say .267"... so I guess someone would have to actually measure the ejected cartridge's bullet...
http://personal.stevens.edu/~gliberat/carcano/emary.html
The primary loading for the cartridge throughout its service was a 162-grain full metal jacket, round nose bullet measuring nominally .267" diameter
The CIP minimum specification diameter for the 6.5 mm Carcano barrel is .256 in / 6.50mm. The groove diameter of the barrel is where a considerable amount of ignorance arises in the Carcano rifle. Nearly every other 6.5mm caliber has a groove diameter of .263 - .264".
The exceptions to this are the 6.5 X 54 MS with a .266" groove and the Carcano with a CIP minimum specification groove diameter of .2677" / 6.80mm. I do not know what the production tolerances were for the Carcano, but based on my knowledge of current rifle manufacturing practice a tolerance of at least +.001" would be used for these dimensions. I have slugged the barrels of approximately 20 different types of Carcano rifles from 3 different manufacturers and have found barrel diameters in good condition rifles typically running from .2680" to .2690"
6.8mm = 0.267717"
6.7818mm = .267"
6.731mm = .265"
6.65mm = 0.261811"
6.5mm = 0.255906"
and he's wrong here too, kind of. it's 6.5278mm which does round down to 6.5mm
Mr. FRAZIER - That is the same as .25 caliber. Such weapons in the United States as the .25-20 Winchester, .25-35, the .250 Savage, and the .257 Roberts, are all of the same barrel diameter, or approximately the same barrel diameter. So a decimal figure of .257 inch is the equivalent of 6.5 mm.