Ammunition Lot Number (ALN) KN-89-C-68 A) I believe is from Naval Weapons Station Crane Indiana which loaded a lot of ammo during Vietnam.
The same projectile body could be finally loaded in several different configurations, each with a Mark and Mod of their own independent of the Mark and Mod of the empty body. The Anti-AIrcraft Common (AAC) was a thin walled high explosive round which could be used against aircraft because it had a mechanical time fuze for airburst (“flak”), hence the “AA” in the name. It also had provisions for a base detonating fuze which would function on impact, allowing the projectile to be effective against shore targets or other ships, the traditional role of base fuzed “common” projectiles.
The AAC shells were the largest part of a the load of a Navy destroyer in the Vietnam era.
The same projectile body with a point detonating fuze and base detonating fuze was preferred for use in shre bombardment (Naval Gunfire Support- NGFS), and a smaller percentage of the magzines would be filled with these.
In addition, shells loaded with Proximity fuzes (sometimes called VT and erroneously “variable time” were carried for exclusive use against aircraft. These typically did not have base fuzes so they would use a different projectile body than the AAC.
Ships also carried a small number of White Phosphorous (WP or “WIlly Pete”) for use as screening or their secondary value as incendiary rounds.
hHey also carried a number of illumination rounds which carried a flare to illuminate a target area. These used a projectile body which was open at the base with a plate secured by pins. Then the mechanical time fuze functioned, it would ignite a small expelling charge which blew the flare and parachute out the base of the shell and ignited the flare.
Additional practice shells were usually carried, often the same projectile body as AAC rounds, but filled with inert material and dummy fuzes and the base fuze cavity plugged. THese were “blind loaded and plugged” (BL&P) or if fitted with a tracer- BL&T.
More projectiels were carried than powder charges since the powder charges were almost always suitable for any projectile. (Special reduced charged were provided when it was desired to fire with a high trajectory (howitzer-like) instead of direct fire as with a tank gun.)
Powder charges were provided in either brass or steel cases, pretty much reflecting whatever was on hand when a lot was loaded at the ordnance facility, and when a ship loaded ammo from the Weapons Station or alongside a supply ship. There was no attempt to mate certain projectiles with certain (brass or steel) cartridge cases. But, powder charges were either Smokeless Powder with a flash reducing additive to reduce the muzzle flash when fired at night (SPDF); or with out the flash reducing stuff as Non-Flashless (SPDN). Ships usually tried to use the non-flashless in daylight missions, but not a real big deal.
Ships also tried to use all projectiles or powder charges from the same lots to reduce the “group size” due to variations in performance. However, it was also common to round up all the odds and ends from various lot numbers and shoot those up and save the good stuff available in quantity. (This was partially motivated by the weekly(?) notifications about ammo classification listing lots which were no longer serviceable, restricted from certain uses, etc, and it was a real pain to go thru the list of lots in the ship’s magazines, and segregate any restricted lots. The fewer different lots on hand, the easier the job was.)
Remember, the 5"/38 projectiles are separate loaded- the powder charge in its cartridge case was thrown (literally) into the loading tray of the gun, and the projectile a bit more gently (if you can be gentle hefting 58 pound projectiles around) dropped into the tray ahead of the powder charge and the projectileman then tripped the lever to cause the rammer to drive the complete round into the chamber, close the breech block and fire the gun (if firing circuits were closed for continuous fire).
The Projectile WAS NOT loaded into the front of the brass or steel cartridge case so it looked like a big .22 cartridge or a lipstick. The cartridge case was sealed at the front by a plug (some cork, some Bakelite) to keep the powder in and dirt and water out and provide a surface to push against the base of the projectile as it was loaded into the chamber. Upon firing the plug broke into tiny fragments blown out of the barrel.
There is no “correct” match of projectiles and cartridge case by date as WW2 stocks were used until exhausted, and the cases were reloaded numerous times. It was common to see 1942 dated cases used with new production projectiles and vice versa.
Enough for now. More to follow.