The cartridge is of the separate-loading Q.F. type consisting of a brass-plated steel case with the percussion primer C/12 n.A. St. and a propellant charge of double base compo-sition arranged in sections to form 5 charges for normal use. These sections are packed in a cylindrical container. A special or super charge, section No. 6, is also used in place of the lower charges. The supercharge is also packed separately in a cylindrical contai-ner.

The steel case, coated with brass, has the model number "6351 St." and the designation of the equipment "21 cm Mrs. 18" stamped in the base. The length of the case is 16.2 in-ches.

The propellant charge, comprising sections No. 1 to 5 inclusive, consists of 15 lb. 14 oz. 1 dr. of double base propellant and a 1 oz. 2 dr. igniter of nitrocellulose powder. These weights are based on a normal charge temparature of 25° C.

Each of the sections is enclosed in a white flat bag of artificial silk excepting the No. 1 section, which consists of two such bags sewn together at four points on the circum-ference, with a pink igniter bag at the base. The bags containing sections Nos. 2 and 3 are semi-circular. All of the remainder are circular. The bags are marked in black to indi-cate the charge numeral, the weight, nature and size of propellant and the place and date of manufacture of the propellant and the filling of the charge. The upper bag of section No. 1 is also marked "Bleidraht im Beutel" to indicate the inclusion of lead wire as a decoppering agent. The charge tempe-rature normal of 25° C, is indicated by the marking "P.T. + 25° C" in red.

Section No. 1 is a composite charge, each of the bags containing a double base propel-lant of the same basic composition (diethylene-glycoldinitrate and nitrocellulose), but of a different shape and size. The propellant in the lower bag is in the form of square flake, whilst that in the upper and in the other sections is in the form of circular discs with a central perforation.

The weights, natures and sizes of propellants, as marked on the bags, are as follows:–

The cylindrical rolled paper container in which this charge, section No. 6, is packed is marked in white, "Sonderkart. 21 cm Mrs. 18".

The charge is contained in a cylindrical bag of white artificial silk, which is choked at the neck and has a pink base containing the igniter composition. The bagged charge is ap-proximately 20 inches long and bears the following marking, in addition to the charge nu-meral "6", in black:– "21 cm Mrs. 18, 15,537 kg Digl.R.P. – G1 – (500 – 5,6/3)". The nor-mal charge temperature, on which the weight of the charge is based, is indicated by the marking "P.T. + 25° C" in red.

The weight of the propellant charge, as indicated by the markings, is 34 lb. 3 oz. 11 dr. The charge consists of a bundle of tubular cords tied in two places with string. The tu-bular cords are approximately 19.7 inches long and 0.22 inches in diameter. The internal diameter of the tube is 0.12 inches. The propellant is of the double base type and con-sists basically of diethylene-glycoldinitrate and nitrocellulose.