ombie84 said:
You can hear the jumps on the 70mm audio bootleg too.
Here's my memory of them (from my recording), as each reel was about 20 mins:
End of reel 1: Luke bringing C-3PO and R2-D2 inside after sale; reel 2 begins with Threepio's oil bath.
End of reel 2: Tarken tells meeting "We will then crush the rebellion with one swift stroke"; reel 3 begins with the discovery of the dead Jawas.
Reel 3 ends after Luke's training session ("You've just taken your first step into a larger world"); reel 4 begins with Tarkin being informed that a rebel base was found deserted.
Reel 4 ends and reel 5 begins during the trash compacter sequence.
Reel 5 ends and reel 6 begins inside the rebel hanger ("All pilots to their stations") prior to the Death Star attack.