Abstract: Allows the reduction in the loss of precision of a discharge caused by the progressive heating-up of the barrel during a long succession of discharges, comprising at least: an interior rifled gunbore (1), an outer sleeve (2) mounted coaxially on the rifled gunbore (1) and configured with a high polar moment of inertia to support the strains in the rifled gunbore (1), while at the same time providing rigidity to the conjoined configuration, and a screwed union (3) adapted for the solid mutual fixation of said pieces. At least two holes (5, 6) are additionally provided which traverse the wall of the rifled gunbore (1) equilibrating the temperatures of said rifled gunbore (1) and said outer sleeve (2), in such a manner as to maintain the initially provided pre-strain of the barrel. The outer sleeve (2) may dispose an aperture for gases (1), adapted for the fitting of a repeat mechanism.