Hawker Siddeley / BAe Harrier

Electrically primed ammunition was adopted to increase the rate of fire desirable for air to air combat. It eliminated the time required for mechanical percussion movements. Albeit milliseconds, the time of the firing cycle, round to round, was higher for mechanical percussion and percussion primer reaction.

I know the 30mm ADEN intimately including ground testing with electronic metering but I know nothing about the 25mm version other than it used all the principles of the 30 but used percussion primed ammo of smaller calibre so I am curious as to how the percussion firing worked.

Time to root out some tech info.....

PETERTHEEATER;158868 wrote:

I know the 30mm ADEN intimately including ground testing with electronic metering but I know nothing about the 25mm version other than it used all the principles of the 30 but used percussion primed ammo of smaller calibre so I am curious as to how the percussion firing worked.

Hope this makes sense:

There was a lever, similar to the ejector lever fitted to the other side of the BCH that acted on a plunger in a modified ejector spring housing. A spigot on the latter engaged in the forked end of a lever that was pivoted in a housing fixed to the rear of the BCH, the other end of the lever fitted in a slot in the firing pin thus the forward movement of the slide drove the firing pin in to the cap. In order to store energy for the first round a tang on the firing pin engaged a toggle that held the firing pin to the rear. In this condition, rather than driving the firing pin forwards, the forward movement of the slide forced the lever pivot out compressing a Belleville washer pack in the process. To fire the gun a solenoid broke the toggle allowing the compressed Belleville washer pack to snap the firing pin forward, firing the gun.

I have to wonder why on earth they just didnt stick with the 30 mm pods?

Thanks for the percussion firing explanation.

I found a document with reasonable detail on the 25. The rate of fire was higher than the 30 (surprise) which Iattribute to the shorter slide travel yet the barrel was longer and the complete gun heavier than the 30 which was undesirable for the VERTOL.

PETERTHEEATER;158901 wrote:

I found a document with reasonable detail on the 25. The rate of fire was higher than the 30 (surprise) which Iattribute to the shorter slide travel yet the barrel was longer and the complete gun heavier than the 30 which was undesirable for the VERTOL.

Do you have a link for that document, be interested to have a read?

ISTR The rate of fire chosen was such that the throw rate for two ADEN 25's matched that of the GAU-12/U over the first x seconds of a burst.

Re the slide travel, it was the same as the 30mm, the piston stroke was shortened and ultimately the piston/gas cylinder redesigned though I never saw that. I'm sure the cylinder and housing were heavier than those of the 30mm and the weight may include that of the blast deflector which attached to the muzzle. There was also the weight of the percussion firing mechanism and solenoid to be taken into account

I found it in SCRIBD under 'Documents' a site which I use a lot. It is titled:

Vol 2 Part 3 Hunter Weapons 103111

There is a section on ADEN 30mm and it is at the back of that.

In a way Im glad the Harrier GR5/7/9 didnt have a gun. It would have meant another aircraft using a different calibre of round. We would have had the Tornado using 27 mm , Jaguar and Hawk with 30 mm and Harrier with 25 mm.

And off topic but I think relevant; was the 30 mm RARDEN cannon on the Scimitar CVRT a development of the ADEN ?

canberra;159098 wrote:

In a way Im glad the Harrier GR5/7/9 didnt have a gun. It would have meant another aircraft using a different calibre of round. We would have had the Tornado using 27 mm , Jaguar and Hawk with 30 mm and Harrier with 25 mm.

And off topic but I think relevant; was the 30 mm RARDEN cannon on the Scimitar CVRT a development of the ADEN ?

No. It was a different action completely and different ammo. It was not belt fed but fired 5 round clip

The 25mm ammo for the ADEN 25 was a standard NATO round used in other systems so apart from foreign supply would not have complicated the inventory much

The RARDEN was loaded with 3 Round chargers. The first was put in and transferred then a second inserted to fully load the gun.

Thanks Alec, I thought it was five. The empty cases were ejected forward and out of the 'turret'.