Bag for carrying a cartridge belt, constructed in the form of a flexible, tubular sheath incorporating the cartridge belt, which is principally made out of woven fabric, and which is closed off by a bag bottom, at a lower end and on the front side, and which is open at the other, upper end, wherein in the region of the open end of the flexible, tubular sheath a bag cover flap is arranged, wherein a fastener is arranged lengthways along the tubular sheath between these two ends around the circumference, which makes it possible to open the sheath along its length, wherein - the closed, tubular, flexible sheath, which is closed at the lower end, on the end face and with a rectangular bag bottom, has a rectangular crosssection, with a bag rear wall, two bag side walls arranged on this bag rear wall opposite to one another, and a rectangular bag top opposite to the bag rear wall, and - this bag top is connected to the bag side walls on both sides, i.e. along both of the long sides, by means of one zip fastener in each case, and - the bag cover flap is comprised of a bag cover adjacent to the bag rear wall, which closes the rectangular opening of the sheath, a fixing piece adjacent to the bag cover and a fastening flap adjacent to the fixing piece, and - a cartridge layer safety plate is arranged inside the bag at the bag cover, adjacent to the rectangular opening of the bag, with a cartridge layer safety clamping element, and - one/or more compression unit/s is/are arranged lengthways along the bag, which if necessary draw the bag rear wall and bag side walls together, and - an internal volume reduction band is arranged inside the bag, reducing its width to some 5 % to 10 % narrower compared to the width of the bag rear wall, whose lengths are terminated at one end by a fixing end and at the other end by a free end, wherein the fixing end is sewed firmly in place inside the bag, on the bag rear wall, at a distance of some 30% to 40% of the overall length of the bag rear wall away from the bag bottom, wherein the free end at the opposite end is fixed adjustably, continuously variable and firmly in place along the bag top, in each case corresponding to the inner bag volume required for the cartridge belt, and - a carry belt is arranged on the outside of the bag, on the bag rear wall. - the closed, tubular, flexible sheath, which is closed at the lower end, on the end face and with a rectangular bag bottom, has a rectangular crosssection, with a bag rear wall, two bag side walls arranged on this bag rear wall opposite to one another, and a rectangular bag top opposite to the bag rear wall, and - this bag top is connected to the bag side walls on both sides, i.e. along both of the long sides, by means of one zip fastener in each case, and - the bag cover flap is comprised of a bag cover adjacent to the bag rear wall, which closes the rectangular opening of the sheath, a fixing piece adjacent to the bag cover and a fastening flap adjacent to the fixing piece, and - a cartridge layer safety plate is arranged inside the bag at the bag cover, adjacent to the rectangular opening of the bag, with a cartridge layer safety clamping element, and - one/or more compression unit/s is/are arranged lengthways along the bag, which if necessary draw the bag rear wall and bag side walls together, and - an internal volume reduction band is arranged inside the bag, reducing its width to some 5 % to 10 % narrower compared to the width of the bag rear wall, whose lengths are terminated at one end by a fixing end and at the other end by a free end, wherein the fixing end is sewed firmly in place inside the bag, on the bag rear wall, at a distance of some 30% to 40% of the overall length of the bag rear wall away from the bag bottom, wherein the free end at the opposite end is fixed adjustably, continuously variable and firmly in place along the bag top, in each case corresponding to the inner bag volume required for the cartridge belt, and - a carry belt is arranged on the outside of the bag, on the bag rear wall.