Deck Gun Ammo

[Sailor Steve]

That's a funny thing; designations from different navies are so, well, different.

In the Royal Navy a 'Common' shell was also called 'Semi-Armor Piercing' (SAP) and was expected to penetrate armor equivalent to 1/3 the shell's diameter. A book I saw once on Fletcher class destroyers made the same claim for US 'HC'. One of the funnier things about the British designations was the brief use of 'SAPCBC', or 'Semi-Armor Piercing Capped British Common'.

Another reference I've seen to 'HC' was that it was designed for shore bombardment, and was meant to penetrate xx amout of concrete. Sorry, but I don't remember the actual amount.

[akdavis]

Well, I brought up the "common" vs. "HC" issue in the RFB thread apparently without properly searching, as what I had found is all right here.

Anyways, I found some more information that might illuminate the topic further. (although this is from an article on modern naval gunnery, it seems many terms have persisted):

ANTIAIRCRAFT (AA) - AA projectiles are designed for use against aircraft they have no base fuze. Otherwise, they are substantially the same as the high-capacity (HC) projectiles described later.

ANTIAIRCRAFT COMMON (AAC) - AAC projectiles are dual-purpose projectiles combining most of the qualities of the AA type with the strength necessary to penetrate mild steel plate (fig. 2, view A). However, AAC projectiles do not have the penetrative ability of common (COM) projectiles. The type of fuzing will depend on the use. Fuze threads are provided in the nose and in the base. AAC projectiles are normally equipped with a mechanical time fuze (MTF) and an auxiliary detonating fuze (ADF). Dual-purpose action is accomplished by a time setting for airburst or by setting MTFs on "safe" or for a time longer than flight to target to permit the base detonating fuze (BDF - delay) to function for penetration. When you substitute a point detonating fuze (PDF) for the MTF, these projectiles are converted to HC for surface burst.


ARMOR-PIERCING (AP) - AP projectiles are designed to penetrate their caliber of class A arrnor plate. A 5-inch projectile will penetrate 5 inches of armor, and so on. They are characterized in most cases by a low explosive-charge-to-total-weight ratio and by their windshields and AP caps. Windshields are light nosepieces of false ogives designed to give suitable flight characteristics - they are made of mild steel, steel stamping, or aluminum. Windshields are screwed to the AP cap and are staked in place. AP caps are made of the same kind of steel as the projectile bodies. The cap breaks down the initial strength of the armor plate and provides support to the pointed nose of the projectile as it begins to penetrate the target. The cap also increases the effective angle of obliquity at which the projectile may hit and penetrate. The cap is peened and soldered to the nose. AP projectiles are fuzed only in the base. The fuzes must not be removed except at ammunition depots. Powdered dye colors are loaded in the windshield of most AP projectiles. These dye colors allow a firing ship to identify its splashes, since each ship is assigned a specific color. The dye is placed inside the windshield in a paper container. There are ports in the forward portion of the windshield that admit water when the projectile strikes the surface and breaks the port seals. Other ports in the after portion of the windshield are pushed out by pressure of the water inside the windshield. The dye is dispersed through these after ports.

COMMON (COM) - COM projectiles are designed to penetrate approximately one third of their caliber of armor. A 5-inch projectile would penetrate 1.66 inches of armor, and so on. They differ from AP projectiles in that they have no hardened cap and have a larger explosive cavity.

HIGH CAPACITY (HC) - HC projectiles are designed for use against unarmored surface targets, shore installations, or personnel. They have a medium wall thickness and large explosive cavities. Large HC projectiles (fig. 2, view D) are provided with an auxiliary booster to supplement the booster charge in the nose of the main charge. With threads in both the nose and base, HC projectiles may receive a variety of fuzes or plugs to accomplish different tactical purposes. An adapter ring (or rings) is provided on the nose end of most HC projectiles to allow installation of PDFs or nose plug and ADFs with different size threads. An adapter is removed for larger fuzes. HC projectiles are normally shipped with a PDF installed in the nose. The base fuze that is shipped installed in the projectile may not be removed except at an ammunition depot.

HIGH EXPLOSIVE (HE) - Small caliber projectiles with an HE designation are designed to receive a large explosive charge. structurally, they resemble the HC type in larger caliber projectiles. They have no base fuze; a nose fuze is issued installed in the projectile.

http://compass.seacadets.org/pdf/nrtc/sn/14067_ch6.pdf

If one did want to have both types of projectile for the 4"/50, it seems you could use the "AA" slot for the second type, as the 4" was not a DP gun.

Edit: and here is an older source that gives some context:
http://books.google.com/books?id=zjF...ZsKICHfc&hl=en

[Nisgeis]

Ah, nice. I did wonder what the difference between HE and HC was, as they both have more explosive. Especially as the Razorback report mentions them both. Seems it's just a matter of calibre of projectile. Thanks for clearing that one up.

[akdavis]

Here is another pretty definitive source, a USN 1957 manual:

3D7. Penetrating projectiles

This type includes armor-piercing (AP) and common (Com). They are designed to penetrate, respectively, heavy and light armor. The usual bursting charge for these types is Explosive D, which is insensitive enough to permit penetration without premature detonation. The characteristics which make that possible will be described under the heading of penetration in the next chapter.

3D8. Fragmenting projectiles

These projectiles are designed to inflict damage both by blast effect and by fragmentation; that is, breaking up into small high-velocity fragments. They are characterized by thin walls and large cavities for the explosive filled. The general type is subdivided as follows:

1. High-capacity (HC) projectiles (fig. 3D3) are used against unarmored surface targets, shore objectives, or personnel. Since no penetration ability is required, explosives more sensitive than Explosive D may be used.

2. Antiaircraft (AA) projectiles are designed for use against airplanes in flight. Except for fusing they are substantially the same as high-capacity in the larger calibers. In smaller sizes the explosive often contains an incendiary element.

3. Antiaircraft common (AAC) projectiles are a dual-purpose design, combining the qualities of antiaircraft projectiles with the toughness necessary to penetrate steel plating not of armor thickness. The type of fuzing will depend on the use. The walls may be heavier than those of the other thin-walled types, and the filler is usually Explosive D.

[Sailor Steve]

Originally Posted by akdavis

ARMOR-PIERCING (AP) - AP projectiles are designed to penetrate their caliber of class A arrnor plate. A 5-inch projectile will penetrate 5 inches of armor, and so on.

That's an interesting quote, since the 16"/50 will penetrate more than twice its diameter in the best armor at point-blank range, and will penetrate its own diameter at 25,000 yards; and it's not uncommon (if you'll forgive the pun) among naval rifles.
http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm

Another interesting note is that US subs carried common, and maybe 'special common', and not much else, except possibly some starshells. Why? Because there was no 5" AP round made.
http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm

[Nisgeis]

Originally Posted by Sailor Steve

That's an interesting quote, since the 16"/50 will penetrate more than twice its diameter in the best armor at point-blank range, and will penetrate its own diameter at 25,000 yards; and it's not uncommon (if you'll forgive the pun) among naval rifles.
http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm

Don't naval guns have a maximum effective range, or something similar? Perhaps this is the range at which they will penetrate their own diameter in armour.

[Sailor Steve]

Not that I've heard of. Maximum range is as far as they shoot, and the penetration tables will give expected penetrations at given ranges by an armor-piercing shell.