I'll ask again as I did previously.
How does a rifle (more than likely pointed downward at a 45° into the floorboard initially) end up shooting an object that is approx 2.5° lower in elevation than the rifle barrel, firing from someone's armpit?
My #44 answers your #43 -- but i now add the following.
In my below drawing on the side-photo of Queen Mary
..
..If Hickey was as per his standard height (green ellipse shows his head) then he would have to hold the AR15 at almost chin height to do the dirt deed.
..If Hickey's was half way up to being fully erect (blue ellipse shows head height but not necessarily pozzy) then he would have to hold the AR15 say 1" above chest height.
..If Hickey were fully erect (red ellipse) then he would have to hold the AR15 say 4" below chest height.
Now, the (poor 2017 museum copy of the) Bronson footage shows us that at UYB07 (which is equivalent to Z312)(the time of the headshot) Hickey was indeed at that frame half erect (height = blue ellipse).
And, we can't see (too blurry) whether Hickey was ever higher than the blue ellipse he might have been (his auto burst must have started a say half second before Z313, ie at say Z304 or earlier).
The AR15 was laying somewhere on the floor Hickey grabbed it & lifted it up with difficulty in the small space between his feet & the back of O'Donnell's jump seat probly pointed down a bit then he lifted it above O'Donnell's head & swung it around from pointing left to pointing right while shimmying to Hickey's right so that he could get his legs out of the cramped space behind O'Donnell's seat (there was 3" of air between the front of Hickey's seat & the back of the top of O'Donnell's seat)(it was impossible to stand unless Hickey bent forward at say 45 deg while jamming his crutch forcefully into the back of O'Donnell's head)(so, Hickey had to shimmy to the center of Queen Mary).
Hickey would have intended to swing around to the rear towards the TSBD but he didnt get that far Kinney braked Queen Mary & Hickey lurched forward onto O'Donnell (there was one witness) -- & Hickey accidentally squeezed the trigger (he should not have put his finger on the trigger until he had a definite target)(this was Hickey's first day with the AR15)(the AR15 was on SAFETY & cocked & loaded)(according to SSA Floyd Boring & according to SSA Kellerman)(Hickey flicked the selector back past SEMI all the way to AUTO while he was lifting it).
The first shot of the accidental auto burst (of at least 4 shots) went over the windshield of the JFK limo this or a later shot resulted in Tague's bloody left cheek. The AR15 swung downwards as Hickey fell an AR15 usually naturally swings up during a burst, but the up was trumped by the down.
The 2nd last shot of the burst passed over the windshield of Queen Mary & under the divider/rollbar of the JFK limo, & made a huge dent in the chrome trim above & just right of the rear vision mirror it must have been a hollow-point koz a sharp nosed slug would have made a hole.
The last shot of the burst hit JFK in the head, & the remnant slug veered 6 deg & cracked the windshield the remnant slug must have then bounced out onto the street without hitting anyone.
Hickey then fell backward back onto the 2 leather cases his standard half sitting half standing pozzy (a few witnesses)(& as seen in the Bronson footage).
While lifting & swinging he could have had the AR15 under his armpit (as u insist) -- or more likely the AR15 was out in front of him & a little higher than his armpit (my reckoning) bearing in mind that he had to lift the AR15 well up over O'Donnell's head to swing around (so, no, the AR15 was not in Hickey's armpit)(it was out front, & high up).
Re your linked footage the shooter duznt ever place his AR15 anywhere near his armpit this duznt help your argument why did u include that link?
So, which bit(s) of my Hickey theory do u rate as impossible or improbable or whatever?