Are you sure about that?
2) The rifle couldn't be perfectly sighted in using the scope (i.e., thereby eliminating the above overshoot completely) without installing two metal shims (small metal plates), which were not present when the rifle arrived for testing, and were never found.[64] Frazier testified that there was "a rather severe scrape" on the scope tube, and that the sight could have been bent or damaged. He was unable to determine when the defect occurred before the FBI received the rifle and scope on November 27, 1963.
http://en.wikipedia.org/wiki/John_F._Kennedy_assassination_rifle
The scope was offline but it wasn’t bad enough to keep the marksmen from hitting their targets at distances approximating Kennedy’s distance from Oswald. And it’s possible that the scope was sighted better before Oswald disposed of it in his rush to leave the Depository- the scrape on the scope tube could be a sign of that.
The rifle tests are described in this section of the Warren Report. You’ll want to read pages 444-447. It’s a PDF file. They had three men test the rifle, mostly using the scope but once with the iron sights.
http://www.history-matters.com/archive/jfk/wc/wcvols/wh3/pdf/WH3_Simmons.pdf