A mount part for a weapon barrel in a weapon barrel holder having a tubular inner diameter which comprises a first section and an encircling ring-shaped second section which is of greater outer diameter than the first section and than a following third section. The third section has at least one slot. The at least one slot runs substantially perpendicular to the second section. In a particular usage situation, the ring-shaped section has circumferential bevels. This permits usage in a barrel mounting of a multi-barrelled weapon having multiple weapon barrels mounted in a common barrel mounting.