Mr. Cunningham. That is normally. I am talking about a normal blow. The primer is very sensitive. I just named a few of the components, but there are many other compounds in priming mixtures, which are considered secret by each company. But I know that they are explosive mixtures. And the actual striking of the firing pin—with enough force—causes a small detonation to occur. The fire given off, goes through holes in the base, and into where the powder is, and starts the powder burning. It is the gases that are given off when powder burns, which actually cause the bullet to move forward—the pressure builds up behind it, and the bullet goes forward.
Representative Boggs. That is a very good explanation. Thank you.
Mr. Eisenberg. Mr. Cunningham, I wonder whether you could review the pictures with us, and discuss some of the markings which you found in those pictures that led you to decide that the cartridge cases shown therein have been fired in the revolver we have been discussing.
Mr. Cunningham. Yes. The first photograph is a photograph of the breech-face marks, the individual characteristic marks remaining on test cartridge cases obtained from the revolver, and on the C-50 cartridge case that was recovered from the scene. C-50 is on the left. C-15 is on the right. And the hairline, the magnified hairline down the center separates the two cartridge cases.
Mr. Eisenberg. Now, is the invariable procedure to put the test cartridge on the right and the suspect cartridge on the left? Or at least is that your standard procedure?
Mr. Cunningham. I usually put the suspect on the left.
Mr. Eisenberg. Well, in the photographs at any rate, in all the photographs we are going to see, the test cartridge is on the right, and the suspect cartridge is on the left?
Mr. Cunningham. Usually.
Mr. Eisenberg. And what is the magnification of this photograph?
Mr. Cunningham. It is approximately 91 times.