You don’t just pick up a rifle and start shooting!
All marksmen know the indispensable requirement of always first zeroing your firearm to achieve the required accuracy, especially if it has been disassembled as Oswald’s had been.
The captain of my high school rifle team could routinely zero a rifle in one shot. He was on the scope. I would fire once from prone at the center rings of the A-17 type target. He would call out the adjustments (e.g., 2 up, 3 left). My second shot was almost always a bull.
That, my friends, is zeroing a rifle in one shot.
Lee Oswald zeroed his reassembled rifle with the first shot.
That, my friends, is why the first shot ‘missed.’
It was aimed at, and struck, the south curb of Main Street.
The FBI knew that from the beginning.