“Purple Rain” helmer Albert Magnoli will direct horror pic “Primal Scream” for Steven Gagnon’s Gravity Pictures, with Gibraltar Intl. handling foreign sales.“Primal Scream” pits five young adults against a mallet-wielding killer in a 15-hour rampage. Cast includes Victor Webster (“Sex and the City”) and Stark Sands (“Shall We Dance”). Philip Barone and Lawrence Garcia produce for Gravity; exec producers are Gagnon and Randy Paul. Lensing begins in June in New Brunswick. Financing comes from Gravity Entertainment, the financing arm of Gravity Pictures.