You're not too bright, are you?
The two Davis shells were linked, through ballistics, to Oswald's revolver to the exclusion of any other weapon. The chain of possession for these two shells is clear and perfectly intact.
Any issue (if there are any) with the chain of possession of the two Poe shells does not change the fact that the two Davis shells convict Oswald.
http://www.history-matters.com/archive/jfk/wc/wcvols/wh3/html/WC_Vol3_0242b.htmMr. Eisenberg: Now, you said that there were three bullets of Winchester-Western manufacture, those are 602,603, and 605 and one bullet of R.-P. manufacture.
Mr. Cunningham: That is correct.
Mr. Eisenberg: However, as to the cartridge cases, Exhibit 594, you told us there were two R.-P. cartridge cases and two Winchester-Western cartridge cases.
Mr. Cunningham: That is correct.
Mr. Eisenberg: So that the recovered cartridge cases, there is one more recovered R.-P. cartridge case than there was recovered bullet?
Mr. Cunningham: Yes
Mr. Eisenberg: And as to the bullets, there is one more recovered Winchester-Western bullet than there is Winchester-Western cartridges?
Mr. Cunningham: That is correct.
Mr. Eisenberg: How would you account for that?
Mr. Cunningham: The possibility exits that one bullet is missing. Also, they may not have found one of the cartridges.
Representative Boggs: Are you able to match the bullet with the cartridge case?
Mr. Cunningham: It is not possible.
Representative Boggs: So that while you can establish the fact that the cartridge case, the four that we have, were fired in that gun---
Mr. Cunningham: Yes Sir.
Representative Boggs: You cannot establish the fact that the bullets were fired in that gun?
Mr. Cunningham: That is correct.
Representative Boggs: And you cannot--having the cartridge case and the bullet--you cannot match them up?
Mr. Cunningham: No, you can't.
---------------
Mr. EISENBERG. Now, were you able to determine whether those bullets have been fired in this weapon?
Mr. CUNNINGHAM. No; I was not. Mr. EISENBERG. Can you explain why?
Mr. CUNNINGHAM. Yes, sir.
First of all, Commission Exhibit No. 602 was too mutilated. There were not sufficient microscopic marks remaining on the surface of this bullet, due to the mutilation, to determine whether or not it had been fired from this weapon.