Came across the following in the course of my research and knowing some of you have a passion for Japanese ordnance, have reproduced some of the document below.
TimG.
MINISTRY OF SUPPLY
A.R.D. Explosives Report 24/46 May, 1946.
SUMMARY
The design and fillings off the Japanese 4O mm. caseless H.E. round for the aircraft gun HO.301, have been examined at the request of D. Arm. R.D. and the Ordnance Board.
The components and method of filling are shown on A.R.D. Drawing 8074, 4 sheets. The drawings incorporate corrections to preliminary reports from other sources.
The round consists of a shell body divided by a septum into forward and rear cavities for the explosive and propellant charges, and fitted with a snub-nose percussion fuze of improved design. A standard 20 mm. type gaine is carried by the fuze.
The H.E. filling consists of 51 grammes (average) of T.N.T. in the form of three pre-pressed pellets, in two containers, one cylindrical and one, hemispherical, made from wood pulp paper board.
The propellant consists of 9.8 grammes (average) of a double base propellant, N.C./N.G. = 53.8/41.4, stabilised with diphenylformamide. Use of this stabiliser has not been reported previously.
The base of the shell is closed by a steel plug having twelve port holes for emergence of the propellant gases, and housing a small percussion primer in the centre.
The primer filling consists of a gunpowder pellet over a percussion cap of unusual design. A small charge (0.23 grain) of a mercury fulminate/ potassium chlorate/antimony sulphide mixture, in proportions similar to British "A" composition, is pressed into a brass cap shell with a very thin crown (0.007 inch). The cap composition appears to be further sensitised by inclusion of ground glass or similar material. Design tolerances appear to
have been arranged with care to ensure a substantial clearance between the cap composition and the firing anvil.
Firing tests on the pressure bar indicate that the gaine develops greater terminal pressure than the Madsen type, which has a similar contour. The Japanese gaine, however, is considered to be inadequate as applied to ensure detonation of the shell filling.
The report includes observations of the effect of one round when fully detonated, against 1/8 in. mild steel plate; also an analysis of the static fragmentation of a further round, together with a photograph of the fragments
(actual size).
The: results of metallurgical examination of the fuze and primer given in the Appendix the Appendix.
TimG.
MINISTRY OF SUPPLY
ARMAMENT RESEARCH DEPARTMENT
(Foreign Munitions Section)
A.R.D. Explosives Report 24/46 May, 1946.
Japanese 40 mm. caseless H.E. anmnunition
for the aircraft gun HO. 301
The design and fillings off the Japanese 4O mm. caseless H.E. round for the aircraft gun HO.301, have been examined at the request of D. Arm. R.D. and the Ordnance Board.
The components and method of filling are shown on A.R.D. Drawing 8074, 4 sheets. The drawings incorporate corrections to preliminary reports from other sources.
The round consists of a shell body divided by a septum into forward and rear cavities for the explosive and propellant charges, and fitted with a snub-nose percussion fuze of improved design. A standard 20 mm. type gaine is carried by the fuze.
The H.E. filling consists of 51 grammes (average) of T.N.T. in the form of three pre-pressed pellets, in two containers, one cylindrical and one, hemispherical, made from wood pulp paper board.
The propellant consists of 9.8 grammes (average) of a double base propellant, N.C./N.G. = 53.8/41.4, stabilised with diphenylformamide. Use of this stabiliser has not been reported previously.
The base of the shell is closed by a steel plug having twelve port holes for emergence of the propellant gases, and housing a small percussion primer in the centre.
The primer filling consists of a gunpowder pellet over a percussion cap of unusual design. A small charge (0.23 grain) of a mercury fulminate/ potassium chlorate/antimony sulphide mixture, in proportions similar to British "A" composition, is pressed into a brass cap shell with a very thin crown (0.007 inch). The cap composition appears to be further sensitised by inclusion of ground glass or similar material. Design tolerances appear to
have been arranged with care to ensure a substantial clearance between the cap composition and the firing anvil.
Firing tests on the pressure bar indicate that the gaine develops greater terminal pressure than the Madsen type, which has a similar contour. The Japanese gaine, however, is considered to be inadequate as applied to ensure detonation of the shell filling.
The report includes observations of the effect of one round when fully detonated, against 1/8 in. mild steel plate; also an analysis of the static fragmentation of a further round, together with a photograph of the fragments
(actual size).
The: results of metallurgical examination of the fuze and primer given in the Appendix the Appendix.