Special WWII ammo to punch holes in subs' hulls below the water line

Someone mentioned to me meeting a WWII American pilot who used special ammo to shoot at German submarines below the water line in order to sink them. May someone tell me more or point me in the direction of more info? Thanks.

When I first started flying the P3 Orion antisubmarine warfare (ASW) airplane in 1968, one of the antisubmarine weapons we had in our “package” was the 2.75-inch folding fin aircraft rocket (FFAR). We carried these in pods out on the wings and as I recall, each pod had 32 rockets. The gunner in the cockpit could select single rocket or ripple fire. The rockets had hard armor piercing warheads, no explosive, and the idea was that if we caught an enemy submarine on the surface, fully surfaced or partially, we could fire rockets to penetrate the sub’s pressure hull, which meant it couldn’t submerge but was stuck on the surface where it would be easy pickings. If the sub was in the process of submerging when we caught it, the rockets could penetrate some sea water to get to the hull, but not a lot. Firing a ripple of 32 was like a shotgun with a pretty tight choke, and multiple big leaks in the sub’s hull would be deadly. For single firing, we would start shooting short of the sub and just walk the rockets up to meet the boat. You could single-fire as fast as you could hit the trigger button on the pilot’s yoke (control wheel), or you could ripple-fire 128 rockets from all four pods, quite a show as I remember. I got to shoot a lot of these, but just during exercises for crew qualification.

Back then, diesel submarines were a big threat because they are so quiet when submerged on battery power. But diesel submarines have to surface fairly often, at least to snorkel depth, to run the diesel and charge the batteries. The rockets did fine (we were told) on a sub at that depth. The quietest diesel sub was the Canadian Okanagan, or “O-boat,” which we absolutely hated to have to fly against during joint exercises. Nobody could ever catch it.

I’m not certain, but I suspect that there were similar rockets that could be launched from the few ASW aircraft there were toward the end of WWII.

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Is there more info on those 2.75" solid AP?

Mel, do you happen to have images of a P-3 armed with 2.75" rockets/launch pods?

EOD, I don’t know. That was 50 years ago. I’ll go back and see, but it won’t be quick. Maybe. Sksvlad’s pic of a ripple fire is pretty impressive. The “Mighty Mouse” FFAR was also a weapon to be fired at incoming Soviet bombers from U.S. aircraft, as I learned doing research for the Gyrojet book. All this stuff seems to be interconnected.

Another weapon we had that I was fortunate to being able to shoot, was the AGM-12B Bullpup missile, which had lots of HE in its warhead. It was very effective against surfaced submarines or surface ships. We could carry four of them, and the gunner (right seat co-pilot) would launch them visually at a surface target, aiming right at the ship’s waterline. I sank a surplus WWII destroyer escort with one during an exercise after my buddy in the airplane ahead of mine hit the target DE right at the waterline below the bridge. He opened up a big hole, which would have been fatal, and I put my Bullpup right in the middle, blowing out the bottom of the ship, which promptly sank level, not stern high in the air as depicted in the movies.

Great memories for 6 June.

According to the book Guns and Gunners at Shoeburyness by Tony [A.S.] Hill, ISBN 0-86023-660-9 a development called “Shark” was tested there in 1944. It was planned as a defence for merchant ships against U-boats.
Caliber was 4.7 in, projectile length 70-73 in, velocity 500-700 fps. The “unrotated projectiles” were fired entering the sea at an angle of about 5 dgrees. Designs Mk I, Mk II and Mk III existed. A smaller version was called Sharklet.

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Thank you for the information Mel, and thank you for your service.
D-Day 75 years, God Bless all that serves.

Mel, outstanding experience you have! Thank you for sharing.
Indeed the AGM-12 is quite a beast!

Could those 2.75" have been HEAT?

Mel,
Here is more P-3 Orion memories for you. Maintenance hangar at NAS Whidbey Island, sorry for my kids blocking the birds.

Mel, thanks!
I guess no more 2.75" on them today anymore.

The British 3 inch rocket projectile, carried by various RAF fighters and strike planes on ground attack and anti-shipping missions in WW2, was available with 60 lb HE or 25 lb AP (solid) warheads. Originally, it was intended to fire the AP against tanks and the HE against other targets. However, combat experience turned that around: the HE proved more effective against tanks, while the AP was preferred against ships, and submarines on or near the surface. The reason for that was that after striking the water, the AP rocket’s trajectory flattened out and it skimmed along just below the surface, punching a hole through the hull and (for surface ships) potentially through the boiler… So the pilots aimed “short”, knowing that the RP would carry on for some distance underwater.

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Campbell’s Naval Weapons of World War 2 contains some differences. He says that the calibre of Shark was 4 inches, and it was designed for firing from standard 4 inch guns (this makes sense, as this was the standard calibre gun of most anti-submarine escorts in the RN - the 4.7 inch was more of a destroyer gun). It weighed 96.25 lb (about three times as much as a standard 4 inch shell) of which 24 lb was Torpex filling. Overall length was 73.66 inches, of which 53.5 inch was the body, the rest being the finned tail. There were two anti-ricochet nose rings to ensure that the projectile dived under the water on impact. The propellant charge was 1.44 to 1.63 lb depending on gun type, compared with 5 to 7 lb for standard ammo. Shark was intended for firing against surfaced submarines at up to 800 yards, ideally striking the water about 20 yards short. Trials were “highly satisfactory” but it is not known if it was ever used with success.

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How did “anti-ricochet nose rings” work?

Essentially they acted as a kind of ‘hydraulic brake’; when the projectile nose struck the water, the nose ring (which stuck out like a flange around the nose) generated a high drag, pulling the nose down into the water and preventing the projectile from ricocheting off the surface.

Similar measures were taken with air-launched torpedoes to make sure that they didn’t bounce off-target on impact with the water. In this case, the drag was not wanted once the torpedo was running, so the “nose ring” (or equivalent) was designed to fall off on impact, as soon as it had done its job.

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They might be making a comeback, now that semi-active laser homing systems have been developed for the 2.75"/70mm missiles by several manufacturers. These provide extreme precision out to long range and one of them (AKPWS from BAE Systems) is already in US service. See: https://www.baesystems.com/en-uk/product/apkws--laser-guided-rocket

You mean in the AS role?

Vlad, nose rings are used on priorly ogivale shaped warheads and aircraft bombs.
These by nature do bounce off the water surface even at more or less steep angles.
To prevent this from happening and to make the missile enter the water and keep on it’s straight path the nose section has to be more or less cylindrical and will cause some sort of supercavitation. This is then achieved by adding (often welded on) nose rings (in German actually called “Kopfring” = “head ring”).
Here a German WW2 Hs293 anti ship missile:

The Russians had already in WW1 artillery projectiles with nose sections shaped like cups (with small escape holes for compressed air). These were meant to fight surfaced submarines:
diving%20shell

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I doubt that! Could be useful for giving an MR plane or ship’s helo a weapon to hit small boats with from a safe distance, though - those can present quite a threat to naval vessels, as we know (especially in a swarm attack).

Would a guided 2.75" be the solution for a swarm attack? I think it might be difficult to handle several such targets with guided missiles.

As you sure know the UK navy has M134 miniguns on every vessel to defend against small fast boats.