EXPLOSION IN TURRET TWO
Investigation Continued

41.            There were other variously-postulated causes for this casualty, which we discount, as follows:

a.      Improper performance by the turret crew, such as because of inadequate manning or training:  We saw no indications of this whatsoever.  Specifically, the turret was operating in a fully automatic mode, in which momentary crew performance was no factor; their longer-term performance, such as in maintenance and preparation for firing, had been part of an outstanding accomplishment by the ship; and the standard of material maintenance of the 8” battery as seen in the two undamaged turrets was commendable.

b.     Double load or attempted double load of the gun:  The breech was closed and locked, so the load had been completed (and had been so signaled to plot); the rammer could not achieve this if a preceding projectile were seated.  Further, the special procedures required in order to permit a mistaken attempt to double load could not have been completed within the time available, in the firing sequence recorded.  Finally, if a double load had occurred, an unfired cartridge would be at the rear of the case ejection tube; but the case recovered from there appeared to have been fired normally, as distinguished in appearance from the loaded cases which burned elsewhere in the turret as a result of the explosion.

c.      Cook-off:  The firing sequence for this gun (paragraph 21) shows 20 rounds fired in the preceding 65 minutes, which in turn had been preceded by several hours silence; the round in question had been loaded for not more than something on the order of one minute before the explosion.  These conditions are at least an order of magnitude less severe than those considered likely to explode a projectile by cook-off as indicated in OP 1591, reference (p).

d.   Obstruction in the bore, such as from a rotating band or primer extension left from the preceding round:  Considerable experience has seen these blown out the muzzle with the shot from which they came, particularly the rotating band, which starts ahead of the entire volume of propellant gas.  If a detached primer extension were so far to the rear that it didn’t blow out the muzzle, with the gun at 35 deg. elevation (as in this case) it should drop out the breech with case extraction; but this is immaterial to this casualty anyway, because the empty case from the preceding shot was recovered with the primer extension in place in it.  Finally, before the days of decoppering agents in the ammunition, many wartime firing sequences went far beyond the numbers of shots known to build up copper obstructions in the bore, so that obviously in those firings the gun just blew such obstructions out the muzzle without damage.  Comparable results are also reported from Dahlgren tests done with such objects as loose fuzes lying in the bore ahead of the projectile.  In short, we are confident that an obstruction of this nature is the gun bore did not occur in this instance, but that if it had, it would have been unlikely to cause projectile detonation.

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