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40mm Gun Boosted Rocket for Aircraft Application

L

Lewis

Well-Known Member
I need some help on researching an unusual aircraft cannon and it's ammunition. Any help is appreciated.

I have some information I obtained many years ago-probably the 1980s from a retired employee of the USAF Armament Development and Testing Center/Armament Laboratory at Eglin AFB that included a 16mm Film that I have never viewed. I was told the film relates to a 40mm Gatling type weapon intended for use on the A-X ground attack aircraft (later the A-9 and A-10 and then the A-10 with the GAU-8 cannon). I hope to get the film put on a DVD, but the label on the film is

40mm Gun Boosted Rocket
Contract FO8635-69-C-0178
Test Firings of Rounds 119-138
August 1970

This date was in the middle of the Study process for the A-X weapon. The record of the development of the A-10 indicates that GE, TRW, Philco-Ford were proposing 30mm weapons and Harvey Engineering Lab was proposing a 57mm recoiless weapon. There is no mention of a 40mm Gun Boosted Rocket (GBR). The GE 30mm (GAU-8) was selected and then compared to the Oerlikon 304RK 30 mm (GAU-9) before finally being selected for the A-10.

Either there was another contender, perhaps not serious enough to merit discussion in the A-X study written in 2010, but serious enough in 1969 to write a contract to demonstrate the weapon and conduct test firings. The AF Armament Lab at Eglin was in the middle of this competition and was involved in the testing of the 40mm GBR weapon. The weapon was on display for some time at the Armour Research Foundation in Chicago before it was cut up and disposed of.

I am hoping some information like the name of the contractor who developed the weapon & ammunition and the development office will be identified on the intro of the film, but this is probably unlikely.

Has anyone heard of this weapon or any other GBR work in the mid-late 1960s or early 1970s???

I have checked both Dale Davis' book on ammunition developments at the Eglin Armament Lab and Chinn's Vol 5 covering the period 1952-1989 and neither one was helpful.

I am also looking for photos of the Harvey and TRW guns and ammunition considered for the GAU-8.

The purpose of this research is a presentation at the IAA Seminars in April 2014, and a follow-on article in the IAA Journal.

Any assistance or thoughts would be appreciated.

Cheers,
Lew


Thanks for a great Forum!

 
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Any still photos or drawings of the ammunition? There have been a couple of threads on ammunition similar to what you describe, but part of the confusion was not knowing when it was made or what it was intended for. One of the threads was fairly recent, regarding 40mm and 70mm rocket boosted gun ammunition. Or gun boosted rocket ammunition if you prefer. Try the search engine, 70mm should give you a smaller search.
 
I can only help you on a picture of a 30x173 Gau-8 cartridge with rocket assistance. Maybe the same project?
Regards, DJH
 

Attachments

  • 30x173%20GAU_8%20RAP%20AP.JPG
    30x173%20GAU_8%20RAP%20AP.JPG
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Thanks for the ohoto! This is the AAI version of the RAP developed under contract to the Eglin AFB Armament Lab. Original version was by TRW as I remember but did not meet the design intent of the Lab. Covered in Dale Davis' book.

May I use this photo in my presentation?

Cheers,
Lew
 
No photos yet. I sent off the film yesterday to be put on DVDs and with luck will have a photo from that. Round is a 40mm folding fin rocket about 10" long loaded in a heavy steel case with about 3" protruding beyond the casemouth.

Thanks for the recommendation. Searches do not turn up anything under 40mm gun boosted rocket beyond this post. will try 70mm.

Cheers
Lew
 
You can use the picture for your presentation, no problem .Regards, DJH
 
Lewis said:
No photos yet. I sent off the film yesterday to be put on DVDs and with luck will have a photo from that. Round is a 40mm folding fin rocket about 10" long loaded in a heavy steel case with about 3" protruding beyond the casemouth.

Thanks for the recommendation. Searches do not turn up anything under 40mm gun boosted rocket beyond this post. will try 70mm.

Cheers
Lew
Click to expand...

I think these are what the guys were thinking of.

Dave.

http://www.bocn.co.uk/vbforum/threads/85906-Unknown-40mm-rocket-round?highlight=40mm+projectile
http://www.bocn.co.uk/vbforum/threads/85907-70mm-Rocket-projectile?highlight=70mm+gun

EOD posted this link on one of the above threads and I know its 70mm but it may be of interest:
http://www.dtic.mil/dtic/tr/fulltext/u2/144336.pdf
 
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Dave, I looked at these, but the 40mm GBR associated with the testing that led to the GAU-8 had folding fins, but it may have been a derivative of one of these, who knows until we learn more.

Cheers,
Lew
 
not sure if any of these help, I just did a Gau8 deelopment search in the DTIC web site, these were just a few doc's I downloaded

http://www.dtic.mil/dtic/tr/fulltext/u2/a140367.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/b087370.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a090663.pdf
http://www.dtic.mil/ndia/2009gunmissile/7781pulverTuesday.pdf
 
Thanks for all the advise. With some help from a researcher I found the attached article in the Jan 1972 issue of Aviation Week & Space Technology. Still no indication of who the contractor was for the round or for the gun. Maybe the film will have that info when I get the DVDs back. More later

I'm still looking for info on ( or photos of) the TRW 30mm GAU-8 contender and for the Harvey 57mm Recoiless GAU-8 contender. Any ideas???

Cheers,
Lew


40mm AWST-Jan72-LR.jpg
 
from the microfishe "high rate of fire mechanical rocket launcher"

  • abstract :A six-barrel, Gatling type, 40-mm rocket launcher has been designed, built, and fire-tested. As stated in the exhibit, the weapon was to be spring-started, gas-bleed-driven, and was required to reach a rate of 6000 rounds per minute within 0.5 second. To meet these goals, a highly efficient gas drive was developed that would make optimum use of gas pressure. The launcher, which was designed to fire a rocket-boosted round from individual cartridge breeches, was able to employ an open breech configuration.
  • weight of gun : 243 ib
  • lenght of gun : 42 inch
  • lenght of barrels : 29 inch
  • complete round weight : 2.3 ib
  • muzzle velocity : 700-750 FT/sec
  • pressure : 13000 psi , max pressure : 14950 psi40mm gbr.jpg

sorry for the poor quality of the scan
 
Tround, many thanks... Any information on the manufacturer, who tested it, dates, etc? This could be getting warm!

Cheers,
Lew
 
hello lewis

the weapon was manufactured and tested by the general electric co burlington vt armament and electrical systems dept
and the document is dated of october 1967.(final report : 31 Mar 66-30 Apr 67)
The gun is designed to fire at 6000 rpm but during test, it reach "only" 2520 rpm.
it have a 100 round mag.
Infortunately there are not information on the rocket weight and his boosted velocity.
I think that the rocket is fin stabilized. I will try to make a good scan of the rocket tomorrow.
the weapon and his munition being conceived to have a identical recoil to the 20mm m61 vulcan gun.
I have written the most interessante informations.(I can't read the text on my pc)

"those six barrels are clusters coned at an angle of 1.34 to reduce round dispersion as rate change from 0 to 6000 SPM.
theoretical center of impact shift is 7 mils as compared to 35 mils for parallel cluster , for the 14 to 15 rounds that are fired during acceleration.
Of the 25 rockets received , 10 were fired during demonstration and pressure investigation , the remainder were fired in 2 burst with
high speed color film. coverage targets taken at 1000 inch show dispersions for these bursts of 14 and 24 mils (100% all rounds basis).
Rounds are held in linked cylindrical aluminium breeches and are fed in this mode directly into the rotor sprocket" there is contradiction with the rate of fire.I shall go on tomorrow.
 
Fascinating, guys, this is great information.

It just shows what useful research a good forum like this one can accomplish! :congrats:
 
I agree Tony! The firing trial on my film was in 1970 which ties in nicely with the 1967 date of the weapon Tround posted. The drawing of the rounds is similar to the photo from AW&ST that I posted. The gun in the firing trials on the film is probably a 5 barrel weapon, not a 6 barrel but that is a small point. If the 40mm GBR were a GE product, then it is easy to see why they would not push it hard for the A-9/A-10 since it would compete with their GAU-8 contender, but would be in backup if the USAF changed the requirement, or wanted a smaller aircraft.

Hope to see you in HO the end of this week!

Cheers,
Lew
 
40mm mag.jpghello
other scans
the shape of magazine is rather strange for an usage on a fighter.

may be that this weapon is a technological demonstrator.

some other information:"barrels should have a life of 1661 rounds at 6000 SPM... Temperature rise in the barrels when firing 100 rounds in a burst was not to affect performance or accuracy... Cluster rigidity sufficienthly high to hold dispersion to 8 mils(contractor requirement)...
The powder ignitiate and accelerated the round through the breech into the sleeve which contains the seal and finally into the constant twist barrel , during this time or shortly thereafter the rocket motor is actuated."

View attachment 77201View attachment 77202View attachment 77200
 
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