Alliant Techsystems Inc. said Monday that Jay Tibbets has been named senior vice president and interim president of the company’s sporting group, which is based in Anoka, effective immediately.

He replaces Ronald Johnson, who resigned from Alliant on Jan. 31.

The company has not disclosed a reason for Johnson’s departure.

Tibbets joined Alliant in 2000 and is senior vice president of business development for the defense contractor, based in Arlington, Va.

The ATK Sporting Group produces ammunition and shooting accessories for sport shooters, law enforcement and the military. With annual sales of about $1 billion, the unit generates nearly one-quarter of Alliant’s revenue. It employs about 4,000 people, 1,400 of them in Anoka.

Alliant will release its fiscal third-quarter earnings on Tuesday.