So this thread, before being bumped, just dropped off of page two. It's safe to conclude that Richard bailed again after failing to present evidence of Oswald practicing with the rifle. Good old dependable Richard!
Well, he
did have that one practice shot at Walker ...
Seriously, Marina testified to the WC about practicing to a considerable extent (here she is describing both New Orleans and Dallas):
Mr. RANKIN. From what you observed about his having the rifle on the back porch, in the dark, could you tell whether or not he was trying to practice with the telescopic lens?
Mrs. OSWALD. Yes. I asked him why. But this time he was preparing to go to Cuba.
Mr. RANKIN. That was his explanation for practicing with the rifle?
Mrs. OSWALD. Yes. He said that he would, go to Cuba. I told him I was not going with him---that I would stay here.
Mr. RANKIN. On these occasions when he was practicing with the rifle, would they be three or four times a week in the evening, after the Fair Play for Cuba incident?
Mrs. OSWALD. Almost every evening. He very much wanted to go to Cuba and have the newspapers write that somebody had kidnaped an aircraft. And I asked him "For God sakes, don't do such a thing."
Mr. RANKIN. You have told us about his practicing with the rifle, the telescopic lens, on the back porch at New Orleans, and also his using the bolt action that you heard from time to time. Will you describe that a little more fully to us, as best you remember?
Mrs. OSWALD. I cannot describe that in greater detail. I can only say that Lee would sit there with the rifle and open and close the bolt and clean it. No, he didn't clean it at that time. Yes--twice he did clean it.
Mr. RANKIN. And did he seem to be practicing with the telescopic lens, too, and sighting the gun on different objects?
Mrs. OSWALD. I don't know. The rifle was always with this. I don't know exactly how he practiced, because I was in the house, I was busy. I just knew that he sits there with his rifle. I was not interested in it.
Mr. RANKIN. Was this during the light of the day or during the darkness?
Mrs. OSWALD. During darkness.
Mr. RANKIN. Was it so dark that neighbors could not see him on the porch there with the gun?
Mrs. OSWALD. Yes.
Mr. RANKIN. Did you learn at any time that he had been practicing with the rifle?
Mrs. OSWALD. I think that he went once or twice. I didn't actually see him take the rifle, but I knew that he was practicing.
Mr. RANKIN. Could you give us a little help on how you knew?
Mrs. OSWALD. He told me. And he would mention that in passing---it isn't as if he said, "Well, today I am going"---it wasn't as if he said, "Well, today I am going to take the rifle and go and practice." But he would say, "Well, today I will take the rifle along for practice."
Mr. RANKIN. Do you know where he practiced with the rifle?
Mrs. OSWALD. I don't know where. I don't know the name of the place where this took place. But I think it was somewhere out of town. It seems to me a place called Lopfield.
Mr. RANKIN. Would that be at the airport---Love Field?
Mrs. OSWALD. Love Field.
Mr. RANKIN. So you think he was practicing out in the open and not at a rifle range?
Mrs. OSWALD. Yes.
Marina likewise told Priscella Johnson McMillan that she was surprised to see him with the rifle on the porch in New Orleans and that he continued to practice dry firing for three weeks in late August and early September of 1963.
I strongly doubt he practiced live firing much at all. Not only was Carcano ammunition fairly obscure, but I know from personal experience in the 70's that practicing with a large-caliber weapon quickly becomes prohibitively expensive - and more so for Oswald than me. My guess would be that shortly after acquiring the rifle he located a standard box of 20 shells, either new (military surplus) or reloads, along with the clip (military surplus), and this was the only Carcano ammunition he ever owned. He probably fired a few rounds from time to time in the practice Marina described, and the assassination rounds were probably leftovers from the original box. (No evidence for any of this, I realize.)
Dry firing, of course, costs nothing.
I think the assassination was an entirely impromptu, make-do affair. I think he simply retrieved the disassembled rifle from Ruth Paine's, brought it to the TSBD, assembled it, and trusted his limited past experience with the rifle and his considerable experience in the Marines. I'm no more of a marksman than Elmer Fudd, but this was not a difficult shot, even if he just used the iron sight. The only real mystery is the number and timing of the shots. (I'm not wedded to the two-shot theory, but it does make sense and would explain the dented "mystery shell" as being the dry-firing one that was still in the rifle at Ruth's and was ejected when he loaded the first live round.)