SA Frazier does Mathematics

[Robert Prudhomme]

Reading over the WC testimony of FBI SA Robert Frazier, I came upon this passage. He is testifying as to their attempts to identify the mangled bullet recovered from General (retired) Edwin Walker's residence. The WC and SA Frazier are doing their very best to tie this bullet to the alleged rifle of Oswald, the 6.5 mm Carcano.

"Mr. Eisenberg.

Can you describe the general rifling characteristics which you referred to?

Mr. Frazier.

Yes. They consist of impressions from four lands and grooves. The bullet is mutilated on a portion of its surface. However, it can be determined that there were four land impressions and four groove impressions originally on this bullet.

The width of the land impression is 7/100ths of an inch, that is 0.07 inch--whereas the width of the groove impression is 0.13 inch, or 13/100ths of an inch.

The bullet is flattened so that it was not possible to measure its diameter. However, by adding the land width to the groove width, and multiplying by the number of lands and grooves, you can determine the circumference of the bullet and mathematically determine its diameter, which in this case corresponds to 6.5 mm. ammunition, or approximately .267 inch."

Sounds impressive, doesn't it? SA Frazier even has the proper bullet diameter for the 6.5 Carcano bullet of .267" (.268" actually) as opposed to the typical bullet diameter of .264" for all other 6.5mm/.257 calibre rifles.

However, let us check his mathematics out. He tells us the land widths are .07" and the groove widths are .13".

.07 + .13 = .20 and, as there are four of each, .20 x 4 = .80" as the circumference of the bullet.

Diameter is found by dividing circumference by pi so .80 divided by 3.1416 = .254"

Uh oh, it seems SA Frazier has made a slight mathematical error here, arriving at the answer of .267" instead of the correct answer of .254". Or is it more than that? Guess what the figure .254 corresponds to?

Believe it or not, .254" is the bore diameter of every 6.5mm rifle. This measurement is taken from the top of one land in the barrel to the top of an opposing land, as opposed to the Carcano groove diameter of .268", measured from the bottom of one groove to the bottom of an opposing groove.

Could Frazier have been conducting that worst form of science, where the answer is predetermined and the data is altered to match it?

Edited December 1, 2013 by Robert Prudhomme

[John Dolva]

I spent some time on this yesterday and ended up more confused than when started. I'm not a shooter at all so have no experience but I do like a maths 'puzzle'. From the reading I did do it seems there are tables that use the results from land groove measurements to give ideas about barrels and the whole caliber, bore, bullet diameter et.c. is a, to me, confusing mix of things. I think there is an answer but I haven't got it. Hopefully someone will come along to explain it all.

edit typo

Edited December 2, 2013 by John Dolva

[Robert Prudhomme]

It is really simple. When a rifle barrel is made, the maker first drills or "bores" a hole from one end of the rifle barrel to the other. The diameter of this hole becomes the "bore" or "calibre" of this rifle. In the case of the 6.5x52 mm Carcano, this measurement is 6.5 mm or about .255".

The next step in making the barrel is to cut spiral grooves in the hole drilled through the barrel, creating what are known as "rifling grooves".

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTaTZzCixvp-pYBwCdnM3gySCh77z_QNXPzyW7XsQSVx6SrJ4tcgg

As can be seen in this diagram, the rifling grooves create raised sections called "lands" and, of course, grooves. The measurement from the bottom of one groove to the bottom of a facing groove is the "groove diameter" AND is equal to the diameter of the bullet itself. In the case of the 6.5 mm Carcano the groove diameter and bullet diameter are .268" or about 6.8 mm. The measurement from the top of one land to the top of a facing land is the "bore diameter", .255" or 6.5 mm in the 6.5 mm Carcano.

When a bullet is fired down a rifle barrel, the lands cut grooves into the soft material of the bullet jacket. In doing so, they cause the bullet to spin and this gyroscopically stabilizes the bullet in flight.

The 6.5 mm Carcano has four rifling grooves and, subsequently, four raised lands. These will leave a perfect mirror impression of themselves on a fired bullet. If one measures the width of the land and groove impressions left on the bullet, it is possible to extrapolate these figures into a circle with eight arcs (four lands and four grooves). By adding the arcs together, it is possible to arrive at the measurement for the circumference of the bullet and, dividing this by pi (3.1416) to obtain the diameter of this bullet.

This is what SA Frazier has attempted to do with the Walker bullet, only he has made a serious mistake. The width of the four lands, at .07" each, add up to .28". The four grooves, at .13" each, add up to .52"

.52 + .28 = .80"

In other words, the Walker bullet has a circumference of .80". To find the diameter of the Walker bullet, Frazier divides .80" by pi (3.1416) and comes up with a bullet diameter of .267", which is the correct bullet diameter of a 6.5 mm Carcano bullet (.268" actually).

However, if we divide .80 by 3.1416, the actual answer is .255", which is, surprise! surprise! the bore diameter of a 6.5 mm Carcano rifle.

What Frazier has done is mistakenly think he needs to arrive at the figure of .255" for the diameter of the Carcano bullet and has filled in the land and groove figures to allow him to arrive at this number, when the real number he needs to arrive at is a diameter of .268".

If what Frazier is saying is true, Walker was shot at by a smaller calibre rifle than a 6.5 mm Carcano rifle.

Edited December 2, 2013 by Robert Prudhomme

[Ken Davies]

Robert,

Your math and logic are great. Your posts on ballistics are ver helpful for many.

[Robert Prudhomme]

Perhaps I am not making myself clear on this matter. I have caught an FBI agent perjuring himself to the Warren Commission. This is not a "feeling" or a "belief" but hard indisputable mathematical facts. And, as far as I know, I have not seen another person mention this indiscretion before.

By Frazier's own calculations, the bullet recovered from the Walker residence is too small to have been fired from a 6.5 mm Carcano and Oswald is exonerated of the Walker shooting. Are we not just a little excited?

[Blair Dobson]

Perhaps I am not making myself clear on this matter. I have caught an FBI agent perjuring himself to the Warren Commission. This is not a "feeling" or a "belief" but hard indisputable mathematical facts. And, as far as I know, I have not seen another person mention this indiscretion before.

By Frazier's own calculations, the bullet recovered from the Walker residence is too small to have been fired from a 6.5 mm Carcano and Oswald is exonerated of the Walker shooting. Are we not just a little excited?

I'm excited!

good work!