Abstract: Timepiece barrel with a drum coaxial to a barrel arbour in a direction arranged to confine a barrel spring hooked to the drum and to a core coaxial to the barrel arbour and guided thereon. The core pivots in a bore of the drum, and includes a first stopping surface limiting the axial travel of the core, in the direction, relative to an inner face of the drum, and a second stopping surface opposite the first and limiting the axial travel of the core, relative to an outer face of the drum, which is arranged, on the one hand, imprisoned between the first stopping surface and the second stopping surface, and on the other hand to pivot freely about the core.