That’s a good point from Jack, and it was a leap of speculation on my part about Oswald possibly using a drill press to screw the mount onto the rifle .
If it was that sloppy a job, then it would have been evident when they examined the rifle that the mount had not been attached by a gunsmith.
The only question left then is how probable it is that the scope of the MC rifle could be banged into something such that it causes the scope to be only partially out of alignment relative to the fixed mount, yet able to be aligned once the angle of the mount was changed by using shims.
If that’s a plausible option ( verified perhaps by an actual experiment) then it narrows the reasons for the misalignment of the scope to either Oswald doing it or the conspirator doing it or the conspirator not knowing the scope was out of alignment.
However it could also have been a scope that was PREVIOUSLY banged/ damaged by Oswald many months prior to Nov 22/63, which would leave 2 options:
1. Oswald intentionally used the rifle and assembled the rifle with scope knowing it was out of alignment.
2. Someone else fired the rifle and did not realize the scope was out of alignment until time of shooting.
3. Someone else fired the rifle and DID know the scope was out of alignment.
4. Someone else preplanted the rifle not intending to fire it, and either the scope was already misaligned, or it was damaged as the conspirator hid it wedged into the gap of some pallets stacked with boxes.
It’s seems improbable that a conspirator shooter with intent on firing an MC rifle that he stole from Oswald would not have checked out the alignment and test fired a few shots before he used the rifle to shoot at JFK.
Theoretically the rifle could have been stolen from the Paines garage ( or Oswald’s boarding room) at least 8 hours before the assassination, thus there should have been time to check the condition of the rifle)
Would the conspirator shooter have waited until the very last hour to steal the MC rifle with intent to fire it, thus no time to check it out? It’s highly doubtful imo.
If the intent was just to set up Oswald by leaving the MC rifle , unfired and with a previously misaligned scope, then the purpose of the conspirators is just to cause a diversionary investigation of Oswald, not necessarily to slam dunk getting him to be found guilty by jury.
It appears to me that the FBI demonstrated that Kleins mounted the scope by ordering the same model rifle and scope and finding that it was mounted exactly the same way. I would be willing to bet that both rifles had similar issues with being able to zero the scope at 100-yards. The issue was related to how much adjustment was needed versus how much adjustment was available in the cheap scope. The fact that the mount was offset to the left and well above the bore of the rifle caused more adjustment (from center) than would have been needed for a more typical mount (right above and closer in elevation) to the bore. I also think that if a “banging” caused the scope to be out of alignment, that it would be evident.
Mr. EISENBERG - Now, I now hand you a rifle which is marked C-250. Are you familiar with this rifle?
Mr. FRAZIER - Yes, sir.
Mr. EISENBERG - Can you describe it briefly?
Mr. FRAZIER - It is an identical rifle physically to the rifle Commission's Exhibit 139, in that it is the same caliber, 6.5 mm. Mannlicher-Carcano Italian Military rifle Model 91/38.
Mr. EISENBERG - Did you attempt to determine by use of this rifle whether the scope was mounted on Exhibit 139 by the firm which is thought to have sold Exhibit 139?
Mr. FRAZIER - Would you repeat that, please?
Mr. EISENBERG - Yes.
Did you make an attempt to determine, by use of this C-250, whether the firm which had sold Exhibit 139 had mounted the scope on Exhibit 139?
Mr. FRAZIER - Yes, sir.
Mr. EISENBERG - Can you describe how you made that attempt?
Mr. FRAZIER - We contacted the firm, Klein's Sporting Goods in Chicago, and asked them concerning this matter to provide us with a similar rifle mounted in the way in which they normally mount scopes of this type on these rifles, and forward the rifle to us for examination.
In this connection, we did inform them that the scope should be in approximately this position on the frame of the weapon.
Mr. EISENBERG - Pardon me, Mr. Frazier. When you say "this position," so that the record is clear could you--
Mr. FRAZIER - Oh, yes; in the position in which it now is, approximately three-eighths of an inch to the rear of the receiver ring.
Mr. EISENBERG - On the----
Mr. FRAZIER - On the C-250 rifle.
When we received the rifle C-250, we examined the mount and found that two of the holes had been enlarged, and that screws had been placed through them and threaded into the receiver of the C-250 rifle.
The third hole in the mount had not been used.
We also found that an identical scope to the one on the Commission's rifle 139 was present on the C-250 rifle.
Mr. EISENBERG - Were the screws used in mounting the C-250 rifle in mounting the scope on the C-250 rifle type of screws as those used in mounting the scope on Exhibit 139?
Mr. FRAZIER - Yes, sir.
Mr. EISENBERG - And the holes were the same dimensions?
Mr. FRAZIER - Yes, they are. And the threads in the holes are the same.
Mr. EISENBERG - Mr. Chairman, I would like C-250 admitted into evidence as Commission Exhibit 542.
The CHAIRMAN - It may be admitted.
https://www.aarclibrary.org/publib/jfk/wc/wcvols/wh17/pdf/WH17_CE_542.pdf