So why doesn’t Clint Hill react to a Z150 of Z170 or a Z190 1sr shot? John C . argues the 1st shot missed JFK. OK so maybe since Clint was keeping his eye on JFK and saw no movement of JFK.But How Ciint and the other SS agents don’t hear this loud report of the rifle fire seems improbable imo.
Or If a Z190 shot which hits JFK there would be some neurological response in just a 1/2 sec or less if Dans posted info is valid which would cause JFK to move earlier and thus Clint Hill seeing that earlier movement should have reacted quicker and in Altgens Z255 photo , One of Hills feet should be more off the running board at least.
Clint Hill actually sees JFK "grab at himself" after the first shot.
He saw the moment JFK's arms flew up and he slumped to the left.
In the "When Was JFK Hit?" thread I demonstrated that the first moment we see the beginnings of this reaction in the Z-film is z225.
It is a neuromuscular/reflex reaction to a shot passing through him at z222/223.
Altgens 6 shows Hill apparently looking directly at JFK as he begins to slump to the left. This picture is taken about one and three quarter seconds after the first shot. In three seconds from this moment JFK will be hit in the head as Hill tries to get onto the limo.
Hill is fully aware of the first shot and JFK being hit by it (the idea that Hill and all the other Secret Service agents on board just ignore a missed first shot is too silly to contemplate).
He is about to react to it.
So, let's forget about first shots at z160 or earlier because we would have to believe that Hill (in Altgens 6) stood there gawking at JFK for over five seconds at least.
Even in Andrew's scenario of z190, Hill stands there for over three and a half seconds and still shows no sign of reacting.
It's an eternity in such an intense situation.
When shots are fired people react very quickly.

Landis, Hickey and Ready have all spun around to their right and rear as a result of the first shot, just as they reported doing so.
Hill is staring at JFK who is reacting to being shot.
Was the first shot 3.5 seconds before this pic was taken, or 1.75 seconds?