The suboxide of boron, B6O , has been prepared as a pure crystalline powder and in dense solid masses. The existence of B6O was substantiated from crystallographic, chemical, and density data. Information on x‐ray diffraction, chemical formation, oxidation resistance, and stability is also described. B6O was found to have a greater diamond pyramid hardness than boron carbide.

Important clues about the probable cause of a gun tube explosion were obtained from a fractographic and metallographic examination of the fragments. The size, distribution, and surface markings of fragments may be used to localize the explosion and deduce its intensity. Microstructural features such as voids, adiabatic shear, and structural surface alterations also indicate the explosion intensity and further allow a comparison of the tube structure near and away from the explosion zone. These, and other metallurgical characteristics, are illustrated and discussed for cases of accidental and deliberately caused explosions of large caliber gun tubes.