The failsafe rod is for the powder measure. It makes sure that the slide is pulled all of the way to the rear when the press is opened. When the press is closed, the powder measure slide goes forward and dumps powder. The rod makes sure that the slide is physically pulled back to its starting position so it can get refilled with powder.

Get the manual for the RL550 from the Dillon website. Disregard the stuff about the removable tool head and the other parts you don't have. Basically, setup and running them are exactly the same.

FWIW