The information provided by Joe regarding the ballistics appears to me to be to be enlightening with respect to the scope limitations when attempting to zero-in at 100-yards. There are multiple aspects to consider regarding zeroing-in the side-mounted scope. But to focus on one of them, it appears to me that if the scope was originally mounted by using the typical bore-sight method, then, elevation-wise, it should have been closely matched to the stationary iron sight’s 200-meter zero-in distance. This is due to the ballistics calculator showing only about a -0.1” impact (in elevation) from the centerline of the barrel at that distance.
Looking again at the ballistics calculator data for this rifle and ammunition, we can see that at 100-yards the impact of the bullet is 5.76” above the centerline of the barrel (bore sight line). The scope is an inexpensive relatively small (compared with a typical high-powered hunting rifle scope) scope. It is more typical of one we might put on a .22 caliber rifle and use to learn to shoot with (similar to what I had as a teenager). When reading Robert Frazier’s description and diagrams as testified to the Warren Commission, it appears to me that the adjustment necessary (5.76”) to zero-in the scope at 100-yards is close to (if not exceeding) the range of adjustment available in the mechanism of that scope. And I suggest that the description of a “defective” scope that has become common in this case, is not accurate. I believe that a more accurate description would be that the limited range of adjustment of that scope doesn’t allow it (as mounted on that rifle) to be easily zeroed-in at 100-yards.
Taking this further (and making some assumptions) it appears to me that LHO did make some detailed plans before he attempted to shoot General Walker. Also, it seems to me that if the scope on the rifle was defective and/or useless, that he would have taken it off. So, when we look at the ballistics calculator again for the distance of the shot at Walker (only ~100-feet, or 33-yards) the impact of the bullet is only about 2.5” above the centerline of the barrel (bore sight). If I am thinking about this correctly, the available range of adjustment of the scope should allow this much smaller amount (compared to the 5.76” required at 100-yards). But I could be wrong, so please feel free to correct me. So, it seems to me that it is probable that in all the careful planning that was apparently made for the Walker shooting, the distance of the shot should have been noted and estimated. And that the scope could have been zeroed-in at that distance when practice shooting the rifle. And if that is what happened, then it seems to me that (assuming normal careful handling of the rifle) when the rifle was used in Dealey Plaza that the scope was probably still at or close to that setting due to an apparent lack of time to zero-in the rifle again before the shots were taken.
