It would have taken the bullet about 2.4 frames of the Z-film to travel the 88 yards from Oswald's rifle to JFK's head so it was probably fired in the Z310-311 window. That's assuming an average velocity of 2000 fps for those 88 yards. I doubt that is an exact figure but I'm sure it's in the ballpark.
I believe that shot was fired at Z220 and struck about Z222. I base that on a 7 frame difference between the shot fired at Z311 and the camera blur at Z318. Of course if the shot was fired at Z310, that changes the arithmetic by one frame. Frame Z227 is badly blurred so that would indicate a shot fired at Z219-220. That fits with the jacket bulge at Z224 and the simultaneous arm raising by JFK and JBC at Z226.
Yes. I always use the time the bullet struck. Z-153, Z-222 and z-312 (Frame z-313 is clearly close to 20-55 ms after the bullet struck). I could instead use the time Oswald fired. Or the estimated time he chambered the round. But I go with when the bullet struck, or reached the vicinity of the limousine, as my convention, which most people do as well.
I think you are in the ballpark. For years I believed the shot was fired at Z151 based on the blurred frame Z158. However someone recently showed me better evidence that Zapruder reacted at Z155. Not only is that frame badly blurred but the frame jumps between Z154 and Z155. The same jump happens at Z226-227 and Z317-318.
The first shot, whatever frame it was fired at, was by far the most difficult of the three which would explain Oswald's miss. His target would have been almost directly below him, forcing him to raise the butt end of the rifle and fired downward at a target moving across his line of fire. I believe he would have been in a kneeling position because that is one he would have trained for in the Marines. Raising the butt end of the rifle probably would have forced him to raise up out of the kneeling position into a low crouch, an awkward shooting position. To make things even more difficult, he had the tree about to become an issue. He might well have rushed that first shot. That could cause him to pull the trigger as opposed to squeezing it. When a shooter does that, the tendency is to miss low. The shot didn't have to miss that wildly. JFK was on the extreme right side so a miss by a foot or more could cause him to miss everything.
I agree with this pretty much. I think a miss of a few feet, maybe 3 feet or 5 feet might be required. The bullet has to miss the side of the limousine as well, In the 1908 Olympics, shooters missed an entire target the size of a deer, and they had practice, I assume, at shooting at a moving target. And the angular speed was not as great. So i think it is quite plausible that Oswald could have missed by 3 feet, 5 feet or maybe more.
As far as if the shot was at z-151, z-152, z-153, z-154 or z-155, I have not looked into this too carefully. Knowing the approximate frame is good enough to get the angular speed.
