That's a good question. Also, how could anyone else determine that "a bullet completely mutilated" was a steel jacketed 6.5mm Mannlicher Carcano bullet?
"Mr. FRAZIER - I was unable to reach a conclusion as to whether or not it had been fired from this rifle. The conclusion went slightly further than that, in that we determined that the general rifling characteristics of the rifle 139 are of the same type as those found on the bullet, Exhibit 573, and, further, on this basis, that the bullet could have been fired from the rifle on the basis of its land and groove impressions. And, second, that all of the remaining physical characteristics of this bullet, 573, are the same as Western 6.5 mm. Mannlicher-Carcano bullets of the type normally loaded in ammunition made for this rifle, 139. However, the mutilation of the nose of the bullet has eliminated the length characteristics, and it cannot be definitely stated that Exhibit 573 is in fact a Western Cartridge Co. product, but all of the remaining characteristics of base shape, distance from the base to the cannelure, the width of the cannelure, and the overall appearance, coloration, and so forth, are similar to Western ammunition."
[...]
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.
Mr. EISENBERG - What was the direction of the twist?
Mr. FRAZIER - To the right."
So, working backwards from the circumference at the (relatively undisturbed) base the bullet was originally .267" across, within expectations of what you'd see for a WCC 6.5mm Carcano (.268") bullet in that condition. It has 4 sets of lands and groove in a right twist, like a Carcano. Rifling rate appears to be Carcano-consistent:
http://2.bp.blogspot.com/_6kYzhJGqq2M/TIN59nj-vbI/AAAAAAAAFQI/orGtgLLWo-E/s1600/CE573+&+CE399+Comparison.jpgSo, nothing that unequivocally screams "I AM A WCC 6.5MM CARCANO BULLET TO THE EXCLUSION OF ALL OTHER RIFLES," but all measurable parameters are consistent with a WCC 6.5mm Carcano round.
So:
"Mr. EISENBERG - But you do conclude that this was fired from a Mannlicher-Carcano 91/38, or a rifle with similar barrel characteristics?
Mr. FRAZIER - Yes, sir."
If you can find a ballistics expert who can look at the data and differ, please fell free...
