Matt,
Who can prove Oswald was even using that cheap 4x18 scope mounted on the Carano rifle? There is no reason why he could not have used the rifle's iron sights. Faster performance and certainly capable of the accuracy at that distance. I used the same powered scope many times and it's cumbersome and time consuming to use. Now, if Oswald was a shooter on the sixth floor, and did use the scope, you usually have to zero in the scope by making the first shot a test shot to see where the bullet goes. Hence, the tree limb, the overhead sign post, or the concrete curbing on the south side of Elm Street. You don't buy a scoped mail order rifle and commence firing it with that accuracy as shown with General Walker and then Kennedy. He would have to had used and practiced with it once in a while somewhere. I recall his USMC qualification was only marksmen. Could it have been done? Sure. But I don't think we know the full facts, and never will.
BB