The fixed Q.F. round is used in the 3.7 cm anti-tank gun, and has an overall length of 13.3 inches. The weight of the complete round is approximately 2 lb. 14 oz. The shell is painted black.

Armour-piercing shell filled P.E.T.N./Wax.

Base fuze with tracer, model 5103 or 5103* and gaine.

Case model 6331.

Propellant charge of the double base type in tubular form with decoppering agent and nitrocellulose igniter.

Primer percussion, model C/13.

The shell is machined from rolled bar steel and is hardened. The V.D. Hardness figures vary from approximately 600 at the head to 500 at the base. In section the shell has the solid head and small cavity characteristic of piercing shell. The weight of the shell, filled and fuzed is approximately 1.5 lb. The driving band is wholly of copper, and behind it the shell is cannelure for the attachment of the case. The shell is closed at the base by the fuze. The weight of the empty shell is 1 lb. 4 1/2 oz.

The bursting charge consists of approximately 7 drams of P.E.T.N./Wax (85/15), with a two diameter cavity for the gaine and fuze.

Either the fuze "Bd.Z. 5103" or "Bd.Z. 5103*" may be used. A description and drawing of fuze 5103* are included in Pamphlet No. 4 on pages 14 and 15. The drawing, Fig. 8, shows the fuze fitted with an adapter and gaine which are not used in the 3.7 cm shell. Instead the fuze is closed at the front end by an aluminium cap with a central flash-hole, and a gaine is situated above it in the shell. These details are the same as those shown in the drawing of the fuze 5103 (Fig. 25).

The fuze 5103 (Fig. 25) differs from the 5103* in having a delay fitment with a powder pellet instead of being fitted with an aluminium plug with flash-hole.

The gaine has a tubular body of the type used for detonators, with its open end positi-oned over the flash-hole in the cap of the fuze by two washers, apparently of cork. De-tails of the gaine filling are not yet available; this probably consists of P.E.T.N./Wax, with a pressing of lead azide and lead styphnate at the mouth.

The case is 9.8 inches in length and has a slightly shoulder formed by an increase in the taper. The base is stamped "3,7 cm Pak" and with the model number 6331. In some in-stances the model number is followed by a star. Cases bearing this mark are also of brass. Steel cases coated with brass are also used, and bear the usual stamping "St." after the model number. The mouth of the case is attached to the shell by a cannelure.

The propellant charge consists of a bundle of tubular sticks of double base propellant, with an igniter at the base secured by strips of material to the ties of the bundle. In some instances the propellant consists of diethylene-glycoldinitrate and nitrocellulose, and in others nitrogylcerine and nitrocellulose. The charge weight with the first composi-tion (Digl.) is approximately 6 oz. 11 dr., and the diameter of the tube are, external 0.086 inch and internal 0.033 inch. With the second composition (Ngl.) the charge weight approximately 6 oz. 4 dr., and the diameters of the tube are, external 0.098 inch and in-ternal 0.035 inch. With both composition the length of the tubes is 7.4 inches.

The igniter bag is attached to form pockets, and contains approximately 30 grains of granular composition consisting mainly of nitrocellulose, with the addition of potassium nitrate.

The decoppering agent consists of a length of lead (or lead and tin) wire weighing about 77 grains. When the wire is not included the letters "oBD" are stencilled in black on the side of the case.

A description and drawing of the percussion primer, C/13, is included in this pamphlet.