Abstract: An aircraft barrel lay-up assembly is provided comprising a barrel mandrel assembly having a contiguous outer barrel lay-up surface. A minor barrel outer surface element is movable between a minor barrel engaged position and a minor barrel disengaged position and forms a minority portion of the contiguous outer barrel lay-up surface when in the engaged position. A major barrel outer surface element is movable between a major barrel engaged position and a major barrel disengaged position. The major barrel outer surface has a first major barrel surface end and a second major barrel surface end moving together to reduce an effective major barrel outer surface circumference when in the major barrel disengaged position. A composite ply assembly is formed around the barrel mandrel circumference and cured while coincident to form a composite barrel element.