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#41 DougRichards

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Posted 22 May 2017 - 0347 AM

18.5mm is just under 3/4 inch.  With a straight-on hit, penetration by any of these 'pop-guns' should not have been a problem, but the upper curve that was actually above the surface presented extreme angles and a small target to the incoming round.

EDIT:  I see that this is pretty much a repeat of Ken's comment. :P

2d EDIT:  Was there any penetrating hits just below the waterline, where a flatter target angle could have offset water drag?  I just remembered posts that discussed that the Japanese had developed shells that could be effective through water.

 

That is what 3" AP rockets were for.

 

wiki

 

Anti-submarine

Soon after some encouraging results from the initial deployment, trials of the weapon were conducted against targets representing U-boats. It was discovered that if the rockets were fired at a shallow angle, near misses resulted in the rockets curving upwards in seawater and piercing the targets below the waterline. Soon Coastal Command and the Royal Navy's Fleet Air Arm aircraft were using the rockets extensively.

The first U-Boat destroyed with the assistance of a rocket attack was U-752 (Kapitän-Leutnant Schroeter), on 23 May 1943, by a Swordfish of 819 NAS. The rockets used on this occasion had solid, cast-iron heads and were known as Rocket Spears.[8] One of these punched right through the submarine's pressure hull and rendered it incapable of diving; the U–boat was scuttled by its crew. On 28 May 1943, a 608 Squadron Hudson destroyed a U-boat in the Mediterranean, the first destroyed solely by rocket.[3] These rockets were, among other factors, credited with making it too dangerous for the Germans to continue operating their Flak U-Boats, which were initially designed with heavy anti-aircraft weaponry to hold off air attacks.

From then until the end of the Second World War in Europe, Coastal Command and the Fleet Air Arm used the rockets as one of their primary weapons (alongside torpedoes, which, to a certain extent they replaced) against shipping and surfaced U-Boats.


Edited by DougRichards, 22 May 2017 - 1631 PM.


#42 shep854

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Posted 22 May 2017 - 0757 AM

Ken Estes, thanks; that was the discussion I was thinking of.  It's still hard to imagine bullets (even measured in inches) being effective through water.

----

DougRichards, that's really interesting.  Always things to learn! :)  



#43 Ken Estes

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Posted 22 May 2017 - 0812 AM

Shep, this is the work of Nathan Okun on these "Type 91" projectiles, which I see were not limited to BB main guns but also 8" [apparently one hit USS Boise at Cape Esperance] and some lighter 15cm guns.

 

http://www.navweaps....ectile_Data.pdf

 

http://www.navweaps....ch/tech-041.htm



#44 shep854

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Posted 22 May 2017 - 0814 AM

Shep, this is the work of Nathan Okun on these "Type 91" projectiles, which I see were not limited to BB main guns but also 8" [apparently one hit USS Boise at Cape Esperance] and some lighter 15cm guns.

 

http://www.navweaps....ectile_Data.pdf

 

http://www.navweaps....ch/tech-041.htm

Tanks! :)



#45 DougRichards

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Posted 22 May 2017 - 2055 PM

Ken Estes, thanks; that was the discussion I was thinking of.  It's still hard to imagine bullets (even measured in inches) being effective through water.

----

DougRichards, that's really interesting.  Always things to learn! :)

 

Which also leads into: that even though the RN had experimented with unrotated projectiles (ie rockets) from around the late 1930s, and later developments went to war as the 'Land Matress', it appears that there was no naval adoption of a mounting able to fire 3in rockets against aquatic targets, particularly surfaced submarines.

 

The RN of course used rockets on adapted landing craft for shore bombardment.



#46 Chris Werb

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Posted 19 June 2017 - 0430 AM

Late in WW2 we fielded a 4" underwater attack projectile for breech loading guns called "Shark"

 

http://ww2talk.com/i...ojectile.55368/



#47 ickysdad

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Posted 12 July 2017 - 0113 AM

Shep, the IJN developed below water projos, but only for large caliber guns, intending to get under the main belt and into the lighter defense array of BBs. They never had an opportunity to try them.

 Yamato may have hit White Plains with a diving type projectile.....

 

 http://warships1disc...=1#.WWW9xYWcEdU



#48 Ken Estes

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Posted 12 July 2017 - 0741 AM

More likely the mining effect of a near miss. A major caliber hit by a diving projectile would have caused very heavy damage, likely sinking a CVE if it exploded. See pp. 117-19.

 

http://www.damagecon...other CVE's.pdf



#49 ickysdad

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Posted 12 July 2017 - 1037 AM

More likely the mining effect of a near miss. A major caliber hit by a diving projectile would have caused very heavy damage, likely sinking a CVE if it exploded. See pp. 117-19.

 

http://www.damagecon...other CVE's.pdf

 

More likely the mining effect of a near miss. A major caliber hit by a diving projectile would have caused very heavy damage, likely sinking a CVE if it exploded. See pp. 117-19.

 

http://www.damagecon...other CVE's.pdf

 

Do you have Rob Lundgren's book? it's a pretty good read on the issue. He used and provided a far more detailed report then the one you linked to .

 

   http://warships1disc...=1#.WWW9xYWcEdU



#50 whelm

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Posted 10 October 2017 - 0138 AM

 


All rounds for the gun were 5.9kg, with MV of 823 m/s [2700 fps] so penetration would be superior to US Army 3-inch ammo; Rich has some details on this, maybe with penetration figures, which might be found in Campbell, Naval Weapons of WWII.

 

 

 

Yes, somewhere I think I have the comparative penetration values derived from the postwar Navy tests at Dahlgren in 1947. However, the epiphany was not the penetration, it was the Navy finding the "3” M62 APC split and broke up when impacting 3” homogeneous armor plate at 30°and 60°obliquity at velocities up to 2,900 feet per second. On examination, the projectiles exhibited variable hardness with soft spots at the nose, contributing to the failures. However, Navy 3” Mark 29-2 AP projectiles did not shatter." On top of that, while the Army Ordnance did react to there own, earlier tests in 1943 to improve the hardness specifications for 90mm AP that resulted in the (too late for the war) development of the AP T33, no effort I know of was made wartime to improve the specifications for 3" M62 APC or 90mm M82 APC. Nor did it seek to solve the problem with premature firing of its BDF found in the Showburyness tests of May 1944. Instead, Army Ordnance went with HVAP as the solution and ignored its problems.

 

 

They did have development programs for a number of weapons to improve general APC design over the war.

 

75mm

APC T29 redesign of M61 around spring/summer 1944

 

Objective of increasing the wall strength to the rear of the driving band, 75mm APC M61 is being redesigned with a narrower explosive cavity and smaller fuze seat. Gave better penetration then standard M61. Design of shell near identical to 3" T17E1 so testing halted while work was done on that.

 

as the relatively low velocity 75mm is going out of fashion, project was terminated in 1945.

 

 

3"

APC T17 redesign of M62

 

Project to improved performance of the M62. Reduced diameter and increased length of explosive cavity. mechanical failure in shell body resulting from peculiarities in heat treatment from one manufacturer, an investigation was instituted but project ended up being closed 1945

 

 

90mm

APC M82 trial of M68 B.D. fuzes

 

A trial happened at Aberdeen on 3rd June 1944 to verify accuracy of British report on fuze failure in 90mm APC rounds.
a number of rounds were tested at various velocities to simulate ranges against a 4 inch plate at 30 degs. One partial failure out of 9, the rest functioned fine.

 

 

APC M82 increased performance

 

Original intention to achieve MV of 2850 f.s. using M2 propellant, had to change when excessive erosion using M2 propellant observed. A switch was made to M1 powder giving a velocity of 2800 f.s. with high density loading required for propellant ignition difficulties with M23 primer resulting in switching to T33 primer, T33 was thought to be mechanically weak and not standardized resulting in T36 primer.

 

Penetration of homogeneous armour at 30 deg at a range of 2100 yds. is claimed to be increased from 3.7" to 4.25" as a result of increase in velocity from 2650 to 2850 f.s. summer 1944

 

 

APC T25, T25E1, T26, T27, T28, T28, T35 and T39
 

Designed with the aim to improved the performance of the M82 against 4" and 5" plate at 30 and 20 deg. Only the T26 was better then the M82 against the 4" plate possibly due to it's greater weight. Against the 5" plate all designs were superior except the T27 compared to the M82. The T35 was a 24.1 lb AP projectile fitted with a ballistic cap similar to that used on M82.

 

T25 was redesigned (T25E1) with single radius ogive but having a bump/knob on the nose of the cap in order to provide same thickness of cap formerly used with the blunt nose T25.

 

T35 and T25E1 ammo batch produced with W.D. 4370 steel and given modified heat treatment to give extreme hardness at the point tapering towards the base, firing tests showed inferior performance to M77

Conclusion reached that a solid shot would give overall better results leading to the design of the T39, a solid round with tracer and light weight cap and high hard-ability steel. Design had very hard nose and bourrelet tapering off to hardness of 45 Rockwell C at the base.

Batches produced with both hard and soft caps. T39 round designed essentially for the defeat of heavy homo plate at steep angles without sacrificing performance against lighter face hardened plate.






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