Secondary Armament

California’s secondary armament consists of 8 twin .177" cannons with a firing interval of 2 seconds per turret. Each set of 4 turrets, mounted port and starboard, fire as a group, delivering 24 .177" rounds per cycle of the main cannons. Provisions are being made for rotation, and manually adjusted depression. The final configuration of the cannons remains undetermined. In any case, the performance requirements are that each broadside be able to sustain a full speed salvo exchange for a period of 1 minute, delivering 240 rounds maximum, or 176 rounds nominally.

The internal space restrictions of BB-44 allow for a CO2 bottle of 24 ounces maximum. This is a small supply for such heavy armament. Every ounce of gas needs to be used wisely. With the mains firing 12 7/32" rounds per cycle, and one bank of secondaries firing 24 rounds in the same period, the drain on the gas bottle and main regulator would lead to rapid icing using standard cannons with open breeches. When the gas system ices over, gas flow drops or stops, and the cannons are rendered inoperable, or at least weakened considerably. The design of open breech cannons has built-in leakage, into the magazine, through each barrel’s feed tube. The unsealed condition of the attached magazine further adds to the leakage. All volume not directly related to propelling the round through the barrel, is a bleed of pressure, reduces the cannon’s gas efficiency, and pulls more gas from the main supply, which drops its pressure and leads to icing.

Any gas that can be saved, or not wasted, will help retain pressure in the bottle, and slow the icing condition. To that end, California’s secondaries will incorporate sealed breeches. The most probable design includes a sliding rod that will shift the loaded round from below the feed tube to below the barrel base. Gas is controlled by a series of seals mounted along the length of the rod. Because the leakage is practically eliminated, a smaller accumulator can be used, leading to efficient draw from the main supply, and to a shorter refill time. These cannons may or may not be able to fill quickly enough to provide full powered shots at the maximum rate of fire, 2 seconds. Only testing will determine that. Aside from using MWC-styled restrictor breech cannons, the California Project can see few other methods to match the performance requirements.

Below, you will find an image depicting the first published design concept of the sealed breech secondary cannon. This rendering includes only a cylindrical slide, with no square end for rotation control. Otherwise, the concept reflects the current thinking.

Gas is sealed within the accumulator by the slide and a pair of O-rings. A round drops into the breech, and is delivered to its firing position when the slide has shifted to the left. This happens when trigger gas pressure is delivered to the cavity in the right end of the slide. (This cavity acts as the actuator commonly found on Indiana style cannons.) When the slide has completed its move, pressure from the uncapped accumulator propels the round up the breech tube, and out the barrel. When trigger pressure is released, the return spring forces the slide back to the right, where it seals the accumulator, and captures the next round.

Two units will be mounted on one rotating platform for each twin 5" mount. No decision has been made as to whether these mounts will rotate under R/C command, or be left for manual adjustment as the captain wills. Further enhancements will be published on this page.