Oswald used his first bullet for the indispensable requirement of zeroing (sighting-in) his reassembled weapon.  He gave himself one round and about 10 seconds.  Could he do it?

(1) The captain of my high school rifle team could usually zero a rifle in one shot.

(2) Even without the rigorous Marine Corps training in rifle marksmanship that Oswald received, if it takes you more than five seconds to do this, you have my sympathy.  :-)

No other work— not Posner’s, Bugliosi’s or any other— solves these mysteries.
The Final Truth solves them all and more:

1. Why, when and where that first shot was fired.

2. Where Oswald was headed when confronted by Officer J. D. Tippit.
3. Why Oswald fled from the 30/Marsalis bus after only two blocks.
4. What the FBI knew about the fresh bullet mark on the Main St. curb.
5. Why there were deliberate splices in the Zapruder and the Tina Towner films.

Breaking new ground....

The Final Truth: Solving the Mystery of the JFK Assassination http://www.amazon.com/gp/product/1490350578