GAU-7 : Gun for the F-15

ikke666

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Has any-one pictures or drawings of the proposed GAU-7 caseless ammo gun for the F-15?
I can't find any :'(
 

dannydale

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Closest I ever got was a projectile pic on the excellent quarry.nildram.co.uk site.
 

ikke666

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i've tried to get to the site, but i got a 404 server not found error :'(
did you type an error?
 

Madurai

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Wait! What's this? 27x70B "1950's large-caliber M61 Vulcan variant," you say?
 

Pioneer

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Interesting topic!!

Sorry ikke666, but aftersearching I to am unable to find anything in my books or the web :(

As a side-note - does anyone know how much the GAU-7/A program end up costing at the time of its cancellation?


Regards
Pioneer
 

blackstar

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I'm scratching my head on this because I know that somewhere I have seen this in a book. It was a book about guns, but had a chapter on caseless ammo, including a photograph of the cannon as well as a neat schematic of H&K's prototype caseless ammo rifle. Unfortunately, I cannot remember if I actually have the book or simply checked it out of a library. Searches of my shelves have been fruitless.
 

ikke666

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did you mean this book? ::)
http://www.amazon.de/Die-Story-Entwicklungsgeschichte-einer-High-Tech-Waffe/dp/B0027WQJAE/ref=sr_1_1?s=books&ie=UTF8&qid=1319909454&sr=1-1
 

blackstar

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No, it's not that book. I believe the book was on guns in general (although I think it stopped at a certain caliber, so it did not include artillery), and it had a single chapter on caseless ammo.
 

shaba

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I think there is a picture in george chinns machine gun vol 3 or 4 it is available on the scribd website.
 

red admiral

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There are two pictures of what looks to be a mockup in F-15 Eagle by Jeff Ethell, but I don't have a scanner to hand unfortunately.
 

ikke666

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@red admiral

What's the name /isbn of the book with the pictures? ::) Maybe i can find the book at amazon. ;)

@ shaba

could you please post the link to scribd of these two books please :)
 

overscan

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Jeff Ethell Modern Combat Aircraft 12 : F-15 Eagle (Ian Allan 1981)


P19 has two photos of, apparently, the General Electric GAU-7 installation mockup. The text notes that Philco Ford and General Electric both submitted designs and Philco Ford won, so the mockup is of the losing contender. However it has 5 barrels which contradicts the below:


In an earlier life as an instrumentation techician for the US Gov't, I measured and recorded the behavior of internal ballistics energy on the outside of the barrel of the GAU-7 (caseless ammo, 25 mm gatling gun). It was abandoned due to the mechanical synchronization problem between feeder, loader and rotating chambers at high speeds.

Philco-Ford was competing against GE. In the ammo dept it was Hercules against Brunswick (I think). GE and Philco, I believe were also competing feeders. Each contractor supplied a gatling and a single shot breech loader (for ammo testing). GE's item had six barrels as I recall and Philco was five-barreled. I don't believe the GAU-7 was targeted for the F-15, but I could be wrong. I thought it was an A-10 project. The A-10 was a new project then too.PUT THE FIRE OUT? ARE YOU CRAZY? We ran like fugitives! Pretty much ruined the firing bay it was in, but as I recall, the test item (gun) was unharmed. 'Don't remember which one it was (GE vs Philco).

http://thefiringline.com/forums/showthread.php?t=13967&highlight=GAU-7
 

pathology_doc

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Overscan, I think I've got this book at home. How legal would it be to put a shot or a scan of the relevant page up in the next day or two?
 

overscan

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http://www.dtic.mil/docs/citations/AD0775394


Accession Number : AD0775394
Title : Development and Test of Storage and Feed System for GAU-7/A Gun.
Descriptive Note : Final rept. Mar 71-Jan 72,
Corporate Author : EMERSON ELECTRIC CO ST LOUIS MO ELECTRONICS AND SPACE DIV
Personal Author(s) : Williams,H. ; Gilbert,K.
Report Date : JUN 1972
Pagination or Media Count : 71
Abstract : The report provides a description of the design and a summary of the test results of the 25mm Caseless Ammunition Storage and Feed System developed for the F-15 aircraft. Section 2, supplemented by Appendix 1, gives a functional description of the system and its operation. The manner in which the system design accommodated the differences in direction of rotation, round size, feed interruption, power take-off, control, and physical interface of the two guns is included in the description. Section 3 summarizes the results of the tests performed by the Air Force Armament Test Laboratory at Eglin Air Force Base, Florida, using a gun simulator. Section 4 summarizes the gun firing tests conducted with the General Electric GAU-7/A gun at Burlington, Vermont.
Descriptors : *Aircraft guns, *Ammunition feed mechanisms, *Jet fighters, Caseless ammunition, Loaders, Sprockets, Storage, Firing tests(Ordnance), Simulation, Optimization
Subject Categories : ATTACK AND FIGHTER AIRCRAFT GUNS
Distribution Statement : APPROVED FOR PUBLIC RELEASE
 

overscan

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http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADB024728


Accession Number : ADB024728
Title : Basic Design Analysis of GAU-7/A Telescoped Ammunition.
Descriptive Note : Final rept. 29 Dec 75-31 Mar 77,
Corporate Author : CALSPAN CORP BUFFALO NY
Personal Author(s) : Fisher, Edward B.
Report Date : SEP 1977
Pagination or Media Count : 81
Abstract : A research program was conducted to determine the causes of variability in GAU-7/A telescoped ammunition featuring molded grain propellant and a combustible case. The approach to the problem took the form of a coordinated analytical/experimental effort. a computer simulation of the GAU-7/A round was formulated, coded, debugged, validated and used to help determine the sensitivity of ammunition parameters. The experimental effort generated empirical inputs and functions for use in the model as well as defining and providing insight into the variability problem. The results of this program indicate that (1) inconsistent grain breakup (primarily the aft grain), (2) poorly performing and variable ignition components, and (3) interaction of these with a combustible case and other components easily influenced by moisture are primary contributors to GAU-7/A telescoped ammunition performance variability. (Author)
Descriptors : *AIRCRAFT AMMUNITION, *TELESCOPING STRUCTURES, RELIABILITY, PERFORMANCE(ENGINEERING), MATHEMATICAL MODELS, COMPUTERIZED SIMULATION, MOLDINGS, PROPELLANT GRAINS, IGNITION, COMBUSTIBLE CARTRIDGE CASES, COMBUSTION, HEAT TRANSFER, DIAGNOSIS(GENERAL), AIRCRAFT GUNS, INTERIOR BALLISTICS, OBTURATION(BALLISTICS), SUBROUTINES, GAS FLOW, GUN BARRELS, BOUNDARY LAYER, FIRING TESTS(ORDNANCE).
Subject Categories : COMPUTER PROGRAMMING AND SOFTWARE
AMMUNITION AND EXPLOSIVES
BALLISTICS

Distribution Statement : APPROVED FOR PUBLIC RELEASE
 

shaba

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in volume 5 chinn devotes 2 chapters to the gau-7


[Link removed. While volumes 1-4 were produced by the Navy and are public domain, Volume 5 was published privately and is copyrighted - Admin]
 

overscan

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There are indeed 10 pages on the two GAU-7 contenders in Volume 5 of The Machine Gun by George Chinn. Very interesting information. Scans of this are around; don't link to them, please. Summarising info presented is acceptable.
 

ikke666

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I've found a lot of sites who reference to "Development and Test of Storage and Feed System for GAU-7/A Gun." But i can't find a site that contains the 71 pages. :'(
 

Mark Nankivil

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I have some photos of the prototype F-15 with the gun bay set up for this weapon - will post those images to the thread this evening. Will also check the files and see if there is a photo of the gun and ammo.

Enjoy the Day! Mark
 

flateric

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Here comes
Mark.
Do, do, do.
Here comes
Mark, and I say.
"It's all right!"

Little darling,
The smiles returning
to the faces.
It's seems like years
since he's been here. :)
 

ikke666

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i didn't kwew there were 2 different GAU-7 models. very interesting :)
please continue posting info ;D
 

blackstar

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ikke666 said:
i didn't kwew there were 2 different GAU-7 models. very interesting
There's a quote earlier in this thread:

"Philco-Ford was competing against GE. In the ammo dept it was Hercules against Brunswick (I think). GE and Philco, I believe were also competing feeders. Each contractor supplied a gatling and a single shot breech loader (for ammo testing). GE's item had six barrels as I recall and Philco was five-barreled."
 

Mark Nankivil

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Greetings All -

Not sure this really gives the "look" of the gun as it is a volume mock up, but at least it's something. The drawing also may be of help.

I'll keep looking... Mark
 

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overscan

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That includes the pic from the Jeff Ethel book. The gun mockup is indeed 5 barrelled and combined with the date mean this is a mockup of the Philco Ford model.

The George Chinn book has photos and drawings of the actual guns.
 

Abraham Gubler

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The General Electric 25mm GAU-7/A caseless Gatling gun was developed for the F-15 from 1968 to the end of 1971 in competition with the Philco-Ford gun. General Electric developed the gun, Emerson Electric the 960 round feeder and Hercules, General Motors, Olin and AVCO the ammunition. The GAU-7 was a six barrel and 10 chamber Gatling type gun. RoF was either 3,000 rpm or 6,000 rpm, length: 103.9”, barrel length: 84” and weight: 434 lbs. GAU-7 failed to reliably fire a 150 round burst in either fast or low rates of fire so the Philco-Ford gun was selected for further development.
 

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overscan

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Nice, Abe, but someone already posted most of those :)
 

Abraham Gubler

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PaulMM said:
Nice, Abe, but someone already posted most of those :)
And I was only getting started. I did search for F-15 but this thread didn't even come up on page one of searches... Well I'll forget the aviation guns from Chinn and focus on the Army stuff...
 

Lauge

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Abraham Gubler said:
The GAU-7 was a six barrel and 10 chamber Gatling type gun.
Six barrels and ten chambers? How the Niflheim was that supposed to work ???

Regards & all,

Thomas L. Nielsen
Luxembourg
 

TomS

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Lauge said:
Six barrels and ten chambers? How the Niflheim was that supposed to work ???
I can almost visualize it -- barrels and chambers rotating separately and only coming into alignment for firing. Imagine it like a revolver cannon but instead of one barrel, there are several. This would give a little more time for each chamber to cycle while keeping the barrel mass down. It might give you a higher potential RoF, or a somewhat gentler cycle (and the GAU-7 ammunition was reportedly pretty fragile). But my god, the mechanical complexity this would entail.
 

pathology_doc

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Someone tried to get too clever for their own good. Fifty-odd years down the track, the M61 keeps humming quietly on at 6000 rounds per minute, and it will probably still be humming on when combat lasers go into widespread use and kinetic armament goes the way of the dodo.
 

Colonial-Marine

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Is there any more information about the ammunition itself out there? I recall reading that the cartridges were wrapped in some sort of flame-resistant packaging which had to be stripped before firing. Factoring in everything else, the entire setup must have been very complicated and heavy.
 

TomS

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I came across two papers with interesting material on this.

AFATL-TR-84-03 Historical Development Summary of Automatic Cannon Caliber Ammunition: 20-30 Millimeter

This has a couple of sections specifically on caseless and telescoped ammunition, with some discussion of GAU-7/A (and a lot of other interesting topics).

And then there's one specifically about the GAU-7/A. It discusses a non-consumable case design, which seems to have been a last effort after the caseless/combustible case efforts were dropped.

AFATL-TR-75-16 Basic Design Analysis of GAU-7/A Telescoped Ammunition.

I tried up upload them, but they're too large.
 

Tony Williams

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Colonial-Marine said:
Is there any more information about the ammunition itself out there? I recall reading that the cartridges were wrapped in some sort of flame-resistant packaging which had to be stripped before firing. Factoring in everything else, the entire setup must have been very complicated and heavy.
I have one of the cartridges in my collection; it's basically a cardboard cylinder with the projectile buried inside.

One of the problems with combustible case ammo is that if the magazine gets hit by an enemy shell, the whole lot goes up in fire/explosion. So each round had to be wrapped in a fireproof sleeve which had to be stripped off the round before loading. Far too much trouble...
 

Blacktail

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CTA (Cased Telescoped Ammunition) technology predates the F-15 and GAU-7 by almost two decades, but it never worked.

Not that it stopped the defense industry from trying to use it as a one-way money conveyer belt from the Treasury. They tried to re-purpose and re-package exactly the same technology in the early 1990s, with exactly the same result...;
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA370886

...but they were caught red-handed, and exposed;
http://ciar.org/ttk/mbt/armor/armor-magazine/armor-mag.1997.mj/3tkplant97.pdf

http://www.ciar.org/ttk/mbt/armor/armor-magazine/armor-mag.1998.ja/4sayonara98.pdf

Also, note the letters sections in these issues of Armor Magazine;
http://www.benning.army.mil/armor/armormagazine/content/Issues/1999/ArmorMayJune1999web.pdf

http://www.benning.army.mil/armor/eARMOR/content/issues/1999/SEP_OCT/ArmorSeptemberOctober1999web.pdf


Tony Williams said:
Colonial-Marine said:
Is there any more information about the ammunition itself out there? I recall reading that the cartridges were wrapped in some sort of flame-resistant packaging which had to be stripped before firing. Factoring in everything else, the entire setup must have been very complicated and heavy.
I have one of the cartridges in my collection; it's basically a cardboard cylinder with the projectile buried inside.

One of the problems with combustible case ammo is that if the magazine gets hit by an enemy shell, the whole lot goes up in fire/explosion. So each round had to be wrapped in a fireproof sleeve which had to be stripped off the round before loading. Far too much trouble...
As it happens, that issue was what doomed the famous H&K G11 Assault Rifle of the same general era as the GAU-7, back when CTA was all the rage. The G11's evaluators were quick to disqualify it when they found out about that, as it would be a bit of a downer for a rifleman to have a weapon pressed against his cheek explode like a pipe bomb;
http://en.wikipedia.org/wiki/Heckler_%26_Koch_G11

And guess what the US military is doing now, to try a totally-new approach to ammunition technology? More CTA ammunition!;
http://en.wikipedia.org/wiki/Lightweight_Small_Arms_Technologies


Watch for LSAT to fail in the same way for the same reasons (especially if it's byproducts go into operational service). Also, for CTA technology to be once again taken out of a time capsule in another 20 years, and again portrayed as being new and/or "fixed".
 

Tony Williams

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Blacktail said:
CTA (Cased Telescoped Ammunition) technology predates the F-15 and GAU-7 by almost two decades, but it never worked.
Errm - you do know that the British Army has selected the 40mm Cased Telescoped Armament System for the Warrior MICV upgrade and for the new FRES SV recce vehicle, don't you? It has been exhaustively tested and is due to enter service in 2016. The pic below shows a sectioned APFSDS round, the projectile and the armour it penetrates. It comes from my web article here, where there is lots more about it: http://www.quarry.nildram.co.uk/WLIP.htm



As it happens, that issue was what doomed the famous H&K G11 Assault Rifle of the same general era as the GAU-7, back when CTA was all the rage.
The G-11's technical problems were because it used caseless ammunition, not because it was telescoped. So unlike with the 40CTAS, the propellant lacked the protection of a cartridge case.

And guess what the US military is doing now, to try a totally-new approach to ammunition technology? More CTA ammunition!;
The LSAT programme explored both caseless and cased telescoped ammo. The caseless version never really got going (they bought the G-11 tech package from HK) with only a few hundred rounds fired, but the plastic-cased version has seen 100,000 rounds fired from eight different LMGs. It seems to work pretty well, but is unlikely to lead to a service weapon any time soon, if only because there's no money...

The pic below, from another of my web articles ( http://www.quarry.nildram.co.uk/Assault.htm ) shows the caseless (red) and plastic-cased (black) 5.56mm LSAT ammo belts next to conventional brass-cased ammo:



So basically there are three different types of telescoped ammo, which have different issues depending on whether they are caseless, combustible-cased, or with non-combustible (metal or plastic) cases.
 
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