One of the many pieces of hard, physical evidence of conspiracy in the JFK assassination is the dented shell (CE 543), one of the shells so conveniently found right next to the "sniper's window." (Odd: The gunman hid his rifle but left his rifle shells in plain view right by the window!)
That shell, CE 543, could not have been fired from the alleged murder rifle, and it could not have held a bullet in it. Dr. Michael Kurtz explains:
The third cartridge case, Commission Exhibit 543, contained a dent in the opening so large that it could not have held a bullet in it. . . .
In a letter to the Warren Commission of 2 June 1964, J. Edgar Hoover noted that Commission Exhibit 543 (FBI Number C6), the case with the dent, had "three sets of marks on the base of this cartridge case which were not found [on the other casings]." The case, according to Hoover, had also been loaded into and extracted from a weapon three times. The only marks linking the case to Oswald's rifle were marks from the magazine follower. As noted above, Case 543 could not have obtained the marks from the magazine follower on 22 November, since the last round in the clip must have been the unfired one in the chamber. Furthermore, Commission Exhibit 543 lacks the characteristic indentation on the side made by the firing chamber of Oswald's rifle.
Dr. E. Forrest Chapman, forensic pathologist, who in 1973 was given access to the assassination materials in the National Archives, noted that Case 543 was probably "dry loaded" into a rifle. Since the dent was too large for the case to have contained a bullet on 22 November, it was never fired from Oswald's rifle. The empty case, however, for some unknown reason cold have been loaded into a rifle, the trigger pulled, and the bolt operated. Dr. Chapman discovered this phenomenon through experiments of his own.
Dr. Chapman also noted that Case 543 had a deeper and more concave indentation on its base, at the primer, where the firing pin strikes the case. Only empty cases exhibit such characteristics. The FBI also reproduced the effect. Commission Exhibit 557 is a test cartridge case, fired empty from Oswald's rifle by the FBI for ballistics comparison purposes. It, too, contains the dent in the lip and deep primer impression similar to Case 543.
Thus, the evidence proves conclusively that Commission Exhibit 543 could not have been fired from Oswald's rifle. . . . (Crime of the Century, Knoxville: University of Tennessee Press, 1982, pp. 50-51, emphasis added)
I discuss this in more detail in
The Dented Shell: Hard Evidence of Conspiracy in the JFK Assassination.