0.5 inch/12.7 mm Multipurpose Projectile "Raufoss"

[Scott Kenny]

Interesting mention of Chinn. I was a project engineer tacking his 30mm cannon (IIRC WECOM 30, on the AH-J to replace the GE XM 188 20mm. We flight tested it in low hover at Yuma and it was scary to see the tail boom resonating to the fire rate (?450rpm). We should have noticed that the rate of fire was close to the natural frequency of the engine/rotor/airframe combination.

It never was considered after that. Circa 1972

YIKES!!!!!eleventy-one!!!

I do agree the USAAF was nigh impossible to accept the 20mm until Korea.

Yeah, they didn't face enough heavy aircraft that they had to try to stop with .30cal or .50cal.

Which is why the Russians went to 23mm or 37mm, the Germans to 20mm and then 30mm, and the UK to 20mm.

In retrospect, the USAF drive for the 0.60 cal was failure (IMO) to develop satisfactory HEI round for the 50, combined with early horror stories coming from Korea of F-86s smoking MiGs but not getting fires above 38-40K

I mean, Raufoss-type SAPHEI are not exactly safe to handle. You drop one and it lands point down, chances are really good it will detonate at your feet!

There's no safety in the fuze, or mechanical settings. it's got a firing pin sitting on a primer compound, that compresses away from the primer when the gun fires, then slams into the primer when the round impacts. Boom.

 

[tomo pauk]

I mean, Raufoss-type SAPHEI are not exactly safe to handle. You drop one and it lands point down, chances are really good it will detonate at your feet!

There's no safety in the fuze, or mechanical settings. it's got a firing pin sitting on a primer compound, that compresses away from the primer when the gun fires, then slams into the primer when the round impacts. Boom.

Any source for these claims?

 

[Scott Kenny]

Any source for these claims?

Aside from Raufoss/NAMMO's description of how the round is assembled?

 

[tomo pauk]

Aside from Raufoss/NAMMO's description of how the round is assembled?

It will be a good start. Can you post that description?

 

[Scott Kenny]

It will be a good start. Can you post that description?

Sorry for the crap pic, stupid .png files.

The 12.7 mm Multipurpose projectile differs from the standard design by using a tungsten carbide hardcore to increase penetration capabilities and being encased in a copper jacket. Since Multipurpose ammunition is a fuse-less design and do not have any sensitive primary high explosive components (only secondary high explosive) it does not have the safety risk associated with fused projectiles and does not produce dangerous duds.

 

[tomo pauk]

Sorry for the crap pic, stupid .png files.

No problems.

As we can see, there is no fuse at all on the Raufoss MP ammunition. Thus saying that 'there's no safety in the fuze, or mechanical settings' is wrong by default.
Only the .50 MP round has a hard core in it. The 20mm and bigger MP shells have the shell cavity filled with incendiary mixture in the frontal half, and explosive in the other ~2/3rds of the cavity. In the concept, it is very similar to the Japanese ww2 fuse-less 20mm ammo, however the Japanese ammo have had explosive in the front of the cavity, and incendiary mixture in the back.

 

[Scott Kenny]

No problems.

As we can see, there is no fuse at all on the Raufoss MP ammunition. Thus saying that 'there's no safety in the fuze, or mechanical settings' is wrong by default.
Only the .50 MP round has a hard core in it. The 20mm and bigger MP shells have the shell cavity filled with incendiary mixture in the frontal half, and explosive in the other ~2/3rds of the cavity. In the concept, it is very similar to the Japanese ww2 fuse-less 20mm ammo, however the Japanese ammo have had explosive in the front of the cavity, and incendiary mixture in the back.

Poor phrasing on my part.

There is nothing preventing the Raufoss or the US 20mm SAPHEI rounds from detonating on impact if dropped onto concrete.

No safety shear pin that prevents a fuze from firing without first getting 5000gees of acceleration, for example.

 

[tomo pauk]

There is nothing preventing the Raufoss or the US 20mm SAPHEI rounds from detonating on impact if dropped onto concrete.

No safety shear pin that prevents a fuze from firing without first getting 5000gees of acceleration, for example.

There is no fuse in the 1st place in the 'Raufoss shell'. "Raufoss shell" is called MP shell, as multi-purpose.
Militaries around the world are buying the MP shells, they know better than us amateurs whether the shell is safe for handling or not.

Last but not least, see the issues 72 (pg. 46) and 73 (pg. 52) of the magazine 'Hrvatski vojnik', where the MP ammo is described. Do not worry if the Croatian language is not your cup of tea, the pdfs are OCR-d - even the picture captions - so it is easy to paste the text and translate it. You will also see a picture of the MP shell that hit, head-on, the steel plate when dropped from 15 m high, without detonation.

 

[Scott Kenny]

There is no fuse in the 1st place in the 'Raufoss shell'. "Raufoss shell" is called MP shell, as multi-purpose.
Militaries around the world are buying the MP shells, they know better than us amateurs whether the shell is safe for handling or not.

The USAF has noted that their PGU-28/B SAPHEI projectile, which has similar construction to Raufoss, has a mishap rate 80x higher than USAF safety standards permit, with 24x premature detonations in 12years service, while the previous M56A3 HEI round had a total of 2x detonations over the entire lifespan of the round. Yes, the M56A3 has a conventional fuze.

 

[tomo pauk]

The USAF has noted that their PGU-28/B SAPHEI projectile, which has similar construction to Raufoss, has a mishap rate 80x higher than USAF safety standards permit, with 24x premature detonations in 12years service, while the previous M56A3 HEI round had a total of 2x detonations over the entire lifespan of the round.

Does the PGU-28/B has a similar construction to the .50 MP ammo, or similar to the 20/25/30mm ammo?

 

[TomS]

Does the PGU-28/B has a similar construction to the .50 MP ammo, or similar to the 20/25/30mm ammo?

Similar in some ways, very different in others. The crucial difference seems to be in how the leading incendiary charge is fired. In PGU-289, the RS441 fill is shock sensitive. In Mk 211, the nose incendiary can only fire when a pocket of air in the tip is compressed and heated. And that requires spin to actually create the air pocket in the first place.

PGU-28:



Mk 211: