Anyone watching in Houston, & then running around & down to watch some more at Elm St, would not properly hear Oswald's first shot at pseudo Z105, they would hear Oswald's shot-2 at Z218, & they would hear Hickey's auto burst at Z300-Z312.
Lemmeeseenow, who could that be ---- ah yes, it could be Altgens, & it could be Bell --- they both said that there were 2 shots.
There was no mistaking or not having heard a shot. This was all tested by the HSCA as part of the Sound Analysis. There was no early missed shot. Altgens is specific as to the first shot he heard and JFK’s reaction. The time element of working the bolt of the carcano becomes insignificant with there having been only two shots. Even in your scenario two shots account for all the wounding. Why do you need to try and explain an additional shot that literally has no point at all?
HSCA Volume VIII: Acoustics Study - Analysis of Earwitness Reports Relating to the Assassination of President John F. Kennedy (history-matters.com)
4 .3 Loudness and Apparent Size of Acoustic Image
All observers rated the rifle shots as very very loud, and they were unable to understand how they could have been described as a firecracker or backfire . Only the pistol, which was subsonic, produced a moderate loudness . Practically all the rifle shots, whether fired from the knoll or the TSBD, appeared to be diffuse and to occupy a very large acoustic space . For example, the sound did not seem to come from the sixth floor window of the TSBD, but from the right upper side of the building. This apparently large source location may be a result of acoustic scatter of the muzzle blast - either because of the building in the case of the TSBD or because of the trees in the case of the knoll . Only the pistol shot appears to have a reasonably constrained acoustic image and, for that reason, could be localized with some precision .