For “Dallas,” the magic number is 300--and...

For “Dallas,” the magic number is 300--and counting.

On Friday at 9 p.m., the long-running CBS series will roll out its 300th episode. That represents a whole heap of fussing and fighting for the embattled Ewings of Southfork.

After a slow start in the ratings following its premiere on April 2, 1978, “Dallas” went on to become the most popular prime-time series on television. Those lofty ratings have eroded in the past couple of seasons, but the series continues to win its time period.

It now ranks third in total episodes produced for an hourlong drama, trailing only “Gunsmoke” and “Bonanza.”

In this week’s story, appropriately titled “Three Hundred,” feuding brothers J.R. (Larry Hagman) and Bobby (Patrick Duffy) find themselves trapped in an elevator, with a defiant Bobby in possession of the only source of food or drink--a case of expensive wine.