Yes, but not with the Carcano rifle. The first time he ever used the iron sights of a Carcano rifle, was when he fired the three shots, all of which went high, particularly the third shot. Exactly as to be expected of a rifleman who can line up the iron sights with the target, but does not know that the Carcano will miss high by 5.7 inches at 88 yards.
Being an expert rifleman, as Specialist Miller was, does not mean that he can shoot accurately with all rifles, including the ones he has no experience with. With any expert rifleman, he has to be allowed to become acquainted with his weapon first, before he can demonstrate proficiency with it.
Expecting Specialist Miller to do well with the Carcano, or any rifle he is unfamiliar with, is like expecting the winner of the Indianapolis 500, an expert in driving Indy style racecars, to place in the top three that year’s Monte Carlo race, driving a Formula 1 racecar, of which he is totally unfamiliar with and has never driven until the day of the race when he dashes up and jumps into his Formula 1 racecar and starts it up, assuming he can figure out how to do so.
Ok. fair enough.
In your opinion a NRA Master Marksman who is training & competing in shooting competitions regularly would have a hard time making accurate shots at stationary targets he knows the distances of?
Yet Oswald. who was so clumsy and uncoordinated he was unable to drive a automobile, was able to hit JFK in the back of the neck & back of the head while he is riding in a moving vehicle at a unknown speed & at unknown distances from 60 feet in the air. Miller fired from a 30 foot tower. And there is as much evidence of LHO training shooting the Carcano as there is of Miller practicing shooting it. None.
Obviously you have little practical experience with firearms.