Why should I? It's all nonsense.
You don't even seem to know that the recoil of the rifle would move the rifle off the intended target. Oswald would have to reacquire the target in his scope, place the crosshairs on his intended target, and then squeeze the trigger in order to fire an accurate shot. If he rushed any of these, he's not going to hit his target. What reason would Oswald have to try to fire the third shot in as little time as possible.
I have fired a similar rifle (a WWI Lee Enfield .306) from a standing position. It does pack quite a kick. But Oswald knew that because he had fired it many times before. He knew that he would have a limited time to get up to four shots off. That is why he used the strap and put the rifle on boxes. That keeps the recoil going directly back. With a secure stance the shoulder would have absorbed the recoil without any change in lateral or vertical position. The FBI conducted their own tests with three agents firing three aimed shots using a similar set-up to that found in the SN. See Agent Simmons' WC testimony at 3 H 444 ff. The shots were remarkably accurate on the targets place at distances and angles replicating shots from the SN.
"Mr. SIMMONS.
And against the first target the accuracy observed was about .7 mils, in standard deviation. Against the second target, the accuracy was 1.4 mils. And against the third target, it
was 1.2 mils. Mr. EISENBEBG. Again, could you convert those at a hundred yards to inches?"
Mr. SIMMONS.
0.7 of a mil at 100 yards is approximately 2 inches. 1.4 mils is approximately 4 inches. And 1.2 mils is approximately 3 1/2 inches.""Mr. SIMMONS Yes. And the numbers which I will give you will be the average of two readings on stop watches.
Mr. EISENBEBQ. For each rifleman?
Mr. SIMMONS. For each exercise.
Mr. Hendrix fired twice. The time for the first exercise was 8.25 seconds; the time for the second exercise was 7.0 seconds.
Mr. Staley, on the first exercise, tired in 6 3/4 seconds; the second attempt he used 6.45 seconds.
Specialist Miller used 4.6 seconds on his first attempt, 5.15 seconds in his second attempt, and 4.45 seconds in his exercise using the iron sight."
"Mr. EISENBERG. What were the targets that you used in your calculations?
Mr. SIMMONS. We used two circular targets, one of 4 inches in radius and one of 9 inches in radius, to approximate the area of the head and the area of the shoulders, or the thorax, actually. And a significant point to these calculations to us is that against the larger target, if you fire with the 0.7 mil aiming error which was observed against the first target, the probability of hitting that target is 1, and it is 1 at all three ranges, out to 270 feet.
Mr. EISENBEBG. Can you explain the meaning of the probability being l?
Mr. SIMMONS. Well, the probability is effectively one. Actually the number is 0.99 and several more digits afterwards. It is rounded off to 1. Simply implying that the probability of a hit is very high with the small aiming errors and short range.
Mr. EISENBERG. Now of course this aiming error is derived from the three riflemen who you employed in the tests, is that correct?
Mr. SIMMONS. Yes.
Mr. EISENBERG. Could you proceed to the other two?
Mr. SIMMONS. Using the 1.2 mil aiming error, again at the larger targets, the probability of hitting the target at 175 feet is 1; at 240 feet it is 0.96; and at 270 feet it is 0.92.
Mr. EISENBERG. How would you characterize the second two figures in terms of probability?
Mr. SIMMONS. These also are very high values."