This is pretty close to the mark. The HSCA PEP concluded that Kennedy was hit at Z188-190, but Alvarez much more credibly concluded that JFK was hit at Z226. JFK's reaction right after Z188 was probably in response to being stung on the back of the head by two fragments from the bullet that struck the curb near the limousine (these fragments are visible on the autopsy skull x-rays--they only penetrated a tiny fraction of an inch into the skull--and the only plausible ballistics and forensic explanation for them is that they separated from a bullet outside the limo before they hit the skull).
Beginning at Z226, Kennedy's body is visibly jolted sharply forward, and the position of his hands and elbows--particularly his elbows--changes dramatically, as they are flung upward and forward. The force and speed of these movements of his arms and elbows are quite startling when one compares frame 226, where they are first discernible, to frame 232 just 1/3-second later. Although the WC, and to a great extent the HSCA, ignored these movements, they are among the most dramatic and visible reactions on JFK's part in the entire Zapruder film.
After carefully studying high-quality blowups of the Zapruder film at Life magazine, Connally himself said the impact of the bullet that struck him occurred at Z234.
If Kennedy was hit at Z186 and Connally at Z234, they were hit 48 frames/2.6 seconds apart. If JFK was hit at Z226 and Connally at Z234, they were hit 8 frames/0.45 seconds apart.
But let's take the longer interval of 2.6 seconds. Even that almost certainly would have been beyond Oswald's ability to do and still score two hits in three shots. Yes, if you just fire the Carcano as rapidly as you can, you can fire at a rate of 1.66 seconds per shot, but not with the degree of accuracy required by the lone-gunman scenario.
Using the alleged murder rifle itself, the three Master-rated riflemen in the WC's rifle test--Miller, Staley, and Hendrix--utterly failed to duplicate Oswald's alleged shooting feat. In the first series, Miller took 4.6 seconds to fire three shots, Staley took 6.75 seconds, and Hendrix took 8.25 seconds. In the second series, Miller took 5.15 seconds, Staley took 6.45 seconds, and Hendrix took 7 seconds. They missed the head and neck area of the target silhouettes 20 out of 21 times, even though they were firing from an elevation of only 30 feet (not 60) and even though the targets were stationary!
Yet, we're supposed to believe that Oswald, who was at best a mediocre shot in the Marines, scored two hits in three shots from 60 feet up on a moving target in only 5.56 seconds.
In the 1980s, some WC apologists began claiming that Oswald would have had 8.4 seconds to fire, not 5.56 seconds. But you can only expand the alleged lone gunman's firing time to 8.4 seconds if you assume that he fired at around Z160 and that he completely missed not only JFK but the entire huge limousine with his first and closest shot, the only shot that he had ample time to aim and fire, a proposition that even the WC admitted was unlikely.
Was Oswald a Poor Shot?
https://miketgriffith.com/files/poorshot.htm
How Long Would the Alleged Lone Gunman Have Had to Fire?
https://miketgriffith.com/files/howlong.html
Nellie Connally and Jackie both stated that the first shot hit both men, referencing when JBC cried out Oh No No No, which Gov Connally stated he cried out when he was hit.
Bill Newman, a spectator alongside the car, stated he could not tell which man was hit first by the first shot.
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1.66 seconds per shot was not performed with LHO's carcano but instead a rifle the HSCA thought to be similar.
ADDENDUM C : MEMORANDUM FROM G. ROBERT BLAKEY TO THE SELECT COMMITTEE ON ASSASSINATIONS ON THE MANNLICHER-CARCANO FIRING TEST
MEMORANDUM
TO: ALL COMMITTEE MEMBERS FROM: G. Robert Blakey, Chief Counsel and Director
SUBJECT: Test on Mannlicher-Carcano DATE: March 22, 1979
Yesterday, with the assistance of Sgt. Cecil Kirk and other members of the D. C. Police Department,
the staff conducted a second test of the time necessary to fire two consecutive rounds from a 6.5 mm Mannlicher-Carcano rifle similar to that found on the 6th floor of the Texas School Book Depository on November 22, 1963. The test was conducted primarily to answer the question, would it have been possible for Lee Harvey Oswald to fire two shots in less than 1.7 seconds? Our test shows that it is. As you recall, the estimated trigger pulls for the shots that the acoustics analysis identified as A1 and B2 occurred approximately 1.66 seconds apart. (See my previous memo on correlating the shots) In addition, the test was designed to provide some insight into the difficulty Oswald would have encountered in firing three consecutive shots within 8.31 seconds, at least two of which were less than 1 .7 seconds apart, and at least two of which hit the targets at the noted ranges. From knowledge of the difficulty involved in so shooting, it may be possible indirectly to infer something about the probability, as opposed to the possibility, that Oswald did so. Nevertheless, even the most improbable event may have occurred.
Thus, to answer the ultimate question of whether Oswald did fire the first two shots 1 .66 seconds apart and hit his target at least once in so doing, as much information as available in addition to that gathered in yesterday's testing should obviously be taken into consideration. This, of course, was what the Committee did in reaching its decisions on December 29, 1978, when it reviewed the previous test firing data, together with other evidence such as the acoustics analysis, and the ph sical evidence (e.g. the three empty shell casings found on the TSBD 6th floor. The test was conducted yesterday between 10:00 a.m. and noon at the Lorton Correctional Facility firing range in Virginia. The National Archives, represented by Mr. David Paynter, brought the Oswald rifle (C.E. 139) for use in the test, but bench rest firing tests and operation of the weapon established that it was in too poor condition to be used. (The Committee's Firearms Panel had previously noted the weapon's deterioration since 1963, and their final report reflects the specific nature of the deterioration) . Consequently, a similar weapon was used for
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The eyewitnesses state JFK reacted to the first shot. A large number of them also stated there was only two shots.
Even SA Kellerman, despite his description of a "flurry of shots", by referencing the acceleration of the car placed the second shot as the headshot .
Mr. SPECTER. Would you say the acceleration--
Mr. KELLERMAN. Between the second and third shot. Senator COOPER. Might I ask a question there?
Mr. SPECTER. Yes.
Senator COOPER. A few minutes ago you said in response to a question that when you spoke to the driver the car leaped forward from an acceleration immediately.
Did that acceleration occur before the second shot was fired?
Mr. KELLERMAN. Yes, sir. Just about the time that it came in.
Senator COOPER. About the time it came in?
Mr. KELLERMAN. Yes, sir.
Senator COOPER. Not before?
Mr. KELLERMAN. No. 
