James W. Mullings, 60, a supervisor of experimental machinists in the propulsion research laboratory of the Johns Hopkins University Applied Physics Laboratory, died Friday at Washington Adventist Hospital after an apparent heart attack.

He joined the laboratory in 1955 and worked in the development of equipment used in rocket and jet propulsion engines.

Mr. Mullings was born in Washington. He was a machinist at the Naval Gun Factory from 1940 to 1945. He then spent three years with Modern Displays of Washington, a firm dealing in displays and exhibits.

From 1948 to 1950, he headed his own display and exhibit firm. For the next five years, he was art director with the Evening Star Broadcasting Co. here. He worked briefly in 1955 for P. W. Minnick, a general construction contractor, before joining the Johns Hopkins laboratory.

Mr. Mullings was a founder of Briggs Memorial Baptist Church in Westmoreland Hills. He was chairman of the building committee when the church was constructed in 1950, and again when it was enlarged in 1960. He became a church deacon in 1972.

He is survived by his wife, Mary E., of the home in Takoma Park; two daughters, Roberta S. Hartman, of Silver Spring, and Sharon E. Mullings, of Aspen Hill; a sister, Bertha Ruth Turner, of Silver Spring, and three grandchildren.