Mr. Frazier. It could be differences in the cartridge, but primarily it would be a difference in the amount of setback of the cartridge against the bolt at the time it was fired.
If a cartridge is slightly away from the bolt when it is fired, the primer is blown back out of the cartridge. As the pressure builds up, the cartridge then moves back and reseats the primer in the primer pocket. The manner in which that movement of the primer out and back in is accomplished determines how tightly the primer will bear against the face of the breach after the cartridge has been fired.
It could be that, and it could be just a slight difference in the hardness of the metal of the primer which caused this one to flow back more and be marked more.
Mr. Eisenberg. Could you discuss Exhibit No. 565?
Mr. Frazier. Yes, sir; in Commission Exhibit No. 565 is shown the firing-pin impressions of the test cartridge case from the 139 rifle on the left and the cartridge case, 545, on the right, with a dividing line through the middle separating the primer of one cartridge case from the primer of the other.
No circles have been drawn around this photograph because the marks shown are marks of an abraded area on the firing pin, and are more or less parallel and formed parallel patterns, so that the eye can follow from one line across to the opposite side of the photograph.
In this area shown of the firing pin of the weapon, there was a small scraped area which left these microscopic ridges and grooves shown on the left photograph, and also reproduced in the 545 primer or firing-pin impression on the right side of the photograph.
Mr. McCloy. State for me again what is on the left side? What is this C-14?
Mr. Frazier. This is the rifle cartridge case, the test cartridge case.
Mr. McCloy. The test rifle?