USN 5"/38 Caliber Questions

Hello all, I am new to the forum. I am not an expert on ordnance, so I have some questions about the US Navy 5"/38.

I recently acquired a nice 5"/38 HC projectile from Pete deCoux’s auction #16. The projectile lot # looks to be from 1968 if I am correct (I’ll post some pics of the projectile later). The lot # marking is: ALN KN-89 - C -68A. I think it was made at Kansas Army Ammunition Plant (“KN”).

First, I would like to find a suitable cartridge case to go with it, but have a question about whether it should be brass or steel. If I am not mistaken, I believe these 5" cartridges were often reloaded and reused for many years. If that is the case, would it be correct for a projectile of this era to use either a brass or steel case? I would prefer brass since it looks nicer, but not sure if I would be mixing years of usage. Were brass MK 5 cases still being used in the late 1960’s/early 70’s?

Below is Table A-3 from NAVSEA SW030-AA-MMO-010 TECHNICAL MANUAL, NAVY GUN AMMUNITION, DESCRIPTION, OPERATION, AND MAINTENANCE, 6th Revision, 2009. The pdf is available on

Thanks for your help!


Here are some photos of the projectile.

The rotating band was cut into 3 pieces. As far as I can tell the projectile markings are original, but I wonder if it might have been remarked (wondering if “GCS RESCREENED” might mean that it was relettered?). The rotating band is stamped AA COM, but the stenciled lettering ID’s it as an HC projectile. Are projectiles sometimes changed and used for a different purpose? I also think the fuze is not original (at least if the paint markings are correct).

Hi Larry, beautiful example, thanks for sharing.

Here is more information about the markings:

C: Naval Ammunition Depot, Crane, Indiana (John is correct on the post below, since “KN” is the lot prefix). Date is 1968.
SB: Naval Weapons Station, Seal Beach, California
ACC: Accudyne Corp.

BDF: Base Detonating Fuze
ADF: Auxiliary Detonating Fuze
GCS: Gas-check Seal
IAW N.O.S.C. MSG.: In Accordance With Navy Operational Support Center Message

The re-screened GCS is indicated by the suffix “A” in the lot number. NAVSEA directed this for 5" HE projectiles with gas-check seals before issue.



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.

The markings on the back of the projectile:
WT. 58 LBS CU.FT. 0.4
(I think these are required by federal shipping laws to identify it for Dept of Transportation paperwork)

S B 5-71
281749Z JAN 71

This indicated that it was “GSC re-screeened” in May 1971 at a naval activity “S B” (Saesebo, Japan?) in accordance with Naval Ordnance Systems Command message sent January 28, 1971 at 1749Z (Greenwich mean time).

I am pretty sure this is a screening of all “Composition D” explosive filled projectiles which was a result of an “in-bore” detonation of a projectile in Mount 51 of USS Lowry (DD-770) during gunnery exercises at the NGFS range at Culebra, Puerto Rico on May 29, 1969. One sailor in the mount died and several were injured. Most of the barrel was lost overboard as a result of the explosion, so investigating the cause was very difficult.

Hope that helps.

The projectile currently has a nose fuze (VT Mark 71 Mod 19?) instead of the dummy nose plug.

Projectile markings for the fuze are:
DNP DWG 434038
ADF MK 52-3
BDF MK 83-0

The top line indicates use of a Dummy Nose Plug, drawing number 434048 which would be typical for a High Capacity loading.
The Auxiliary Detonating Fuze Mark 52 Mod 3 and Base Detonating Fuze Mark 83 Mod 0 would be typical on a High Capacity round.

Fede and John, lots of great info! Thanks so much.

I wonder how many ships were still armed with 5"/38 in 1971? Seems like the USS New Jersey was active about that time and I would also assume some destroyers, based on the story about the USS Lowry. I suppose it could have also been sitting in an ammo depot somewhere, too.

There are also markings stamped on the base of the projectile. Some are very hard to read, but the top marks match the projectile ID paint markings MK 52 MOD 0 and next to that it looks like AMC01 (MK 52 is very faint, as is 01). I don’t know what AMC01 means.

On the bottom half it looks like LOT 325 8F (or possibly 8E). The marks other than 325 are very hard to read, so it may actually say something else. It almost looks like 325 was stamped at a different time than the other marks, because it is so prominent.

The inside diameter of the base is also not threaded (and has some deep gouges on one side, visible in the photo above). And there is no groove for the GCS. Could these have been removed as part of the demilling procedure? Since the stencil lists a BDF, I would assume this is the case, but not sure if other possibilities may exist.

I wondered what DNP meant. Now it makes sense. I’ll have to look for a dummy nose plug. I believe it should be yellow to indicate Explosive “D”, is that correct?

Thanks again!


As it was “yellow D” I would say the base fuze was cut out with a water jet with abrasive additives as normal disassembly was no option anymore.

Shell body was made by American Manufacturing Company of Texas, Fort Worth, Texas.


It’s hard to see in the photos, but the fuze is a MOD 15. I found some info on this fuze in the NAVSEA doc I linked to above. Correct usage was in a TP projectile (description, figure A-28 and Table A-2 from SW030-AA-MMO-010 below). I highlighted the usage at the bottom of the table below.

"A- Nonfragmenting Target Practice
(VT-NONFRAG). These projectiles (Figure A-
28) are designed for use in antiaircraft target practice,
particularly against expensive drone targets,
for observing the firing results, frequently without
loss of the drone. A standard projectile body is
filled with inert material around the color burst unit
to obtain the desired weight. The nose of the projectile
is fitted with a VT-RF, proximity fuze,
which is supplemented either by a fuze booster or
an AD fuze. A self-destruct capability is incorporated
into the nose fuze of projectiles D248 and
D249. The self-destruct feature is omitted in projectiles
D250 and D251. A fuze cavity liner separates
the fuze from the color burst unit and inert
filler. The color burst is ignited through the action
of the nose fuzing and the black-powder pellets.
The base of the projectile is either plugged or solid."


Larry- That is a GREAT reference link you provided and I encourage eveyone to download a copy for future reference. Note that Appendices A and F have “historical information” on obsolete rounds, so this is really a great “one stop” reference for virtually all 20th century USN gun ammunition.

The “GCS” marking on the original projectile refers to “Gas Check Seal” inspection which was deemed to be the likely cause of the USS Lowry incident. Factors included the tightness of thread fit between the projectile body and the fuze or base plug, sealant material (luting) used when assembling them together, possibly not fully seating them, and presence and proper installation of the “gas check seal.” The GCS is a copper ring with a lead core which is forced into and undercut area bridging the threaded joint between the projectile body and base fuze/plug. If all those factors are done properly then no problem, but if not…

As far as the service longevity of the 5"38 gun mounts in the U.S. Navy, the WW2 Sumner and Gearing class destroyers, most of which had “FRAM” modernizations in the 1950s and 60s continued in service until decommissioned in the 1970s with a few lingering into the early 1980s. There were also 5"/38 mounts on the battleships as previously noted which saw combat in the Gulf War circa 1991, and some mounts on auxiliary or amphibious ships phased out around the same time as the WW2 destroyers.
However, many of those decommissioned ships were transferred to allies, and 5"/38 ammo would remain in the supply system to support them, as well as war reserve stocks for possible use if mothballed ships were reactivated. So, 5"/38 ammo was still being made and overhauled well into the 1970s.


Thanks for your explanation of the missing base threads. That certainly makes sense and would explain the gouges in the cut. How did they remove the explosive? Is it dissolved in a solvent? And I also wonder how the projectile was originally filled with explosive? I’ve read that some can be melted and poured in place (and maybe removed the same way?), but I’m not sure if “yellow D” was done that way.



Larry, to my understanding the explosive was washed out with the same water + abrasive mix that was used for cutting out the base fuze. (not all explosives can be molten btw)
The issue with yellow D was that it built up so called picrates during storage. Picrates are basically crystals growing due to the composition used and the larger and longer these crystals get the more dangerous they are as when such a crystal simply breaks (hard as glass but thin like a hair) it sets off. And this is the whole problem.
Means the crystals are growing inside the explosive and in the nearest vicinity like the fuze threads. Attempting to unscrew a fuze would then be enough to set off the main charge.
For this reason wather jet cutting was selected to open ordnance containing yellow D.


Great explanation! I found a pic of some picric acid crystals, which I imagine are similar to the crystals you described growing in yellow D. The scary part is that the photo came from a site called Sounds like a recipe for disaster!



I downloaded several Navy documents (everything I could find online for the 5"/38) and I agree that the one referenced in my first post is the most useful. The only place I could find it was on, which I think requires a subscription to download the document (you can view it online without the subscription). But they do have a 30 day trial, so it can still be done at no cost. You just have to remember to cancel before the 30 days are up, otherwise they will charge your credit card.

I think you probably saw at the beginning of Appendix A the detailed procedure for inspecting the Gas Check Seal. They even show diagrams of the conditions you described above. Here’s what a good one should look like:

The document also noted that projectiles made before 1970 needed to be screened, which coincides with the markings on my projectile.

Thanks to you, Fede and EOD, I now know much more about this projectile than I did a few days ago. I love a great history lesson!


Larry, yes, Picric Acid is the most prominent explosive known for building up picrates. By coincidence Picric Acid (also named Melinite, Shimose or Granatfüllung 88) is bright yellow in appearance and was used as a coloring dye in the old days.
Picric acid was used a lot in WW1 and less in WW2 and after that it got dropped for safety reasons.

The liquid and crystals you are showing above normally would cause a bomb squad operation or very skilled and brave chemists who would try to delute the content of the glass cup untill the crystals would solve again.

Here’s another interesting download. The book “U.S. NAVY BUREAU OF ORDNANCE IN WORLD WAR II” has a bunch of good info on ammo development, including the importance of the development of the HC projectile. It can downloaded here:

Below is the title page and a couple of interesting excerpts:

Locations of Naval Ammunition Depots:

Naval gun installations in 1940 and 1945:

Too much info to post here, but thought I would give you a small taste.



Great link/PDF!

Thanks for posting.



I’ve been reading through the WWII ordnance document and there is a wealth of history there. I also came across the companion volume from WWI, which contains quite a few photos:

It seems to be missing a few figures in the first quarter of the book, but the text seems to be intact and there are plenty of good ordnance photos in the latter 3/4 of the book. For example, I didn’t realize that the US Navy had 14" railway guns in France during WWI. A couple of pics are posted below:



And a few more ammo-related figures:




I’ve gotten a bit off-topic from my 5"/38 projectile, so maybe I should post these docs on a new thread.



Hello Fede,

There is still one marking that is a mystery to me. Do you know what “C.G. V” means? It is located next to the aux fuze data ADF MK 52-3 (see second photo at top of post).

I am also wondering if you have a reference document for older Navy ordnance manufacturers? I have MIL-HDBK-1461A, but it only shows what looks like a newer listing for American Manufacturing Company of Texas as AIMCO Defense (symbol AMS listed for both). It doesn’t have the older designation AMCOT (or was AMCOT not an offical Navy marking?).


Best regards,