40mm Gun Boosted Rocket

I have some information, including a 16mm Film that I have never looked at that 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).

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 Armuor Research Foundation in Chicago before it was cut up and disposed of.

I am hoping some information like the contractor 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???

Any assistance or thougths would be appreciated.



I don’t know much about this subject but the following items they may be of some interest.

A recent discussion on the BOCN forum: bocn.co.uk/vbforum/threads/8 … projectile (Subject: 70mm Rocket projectile (GBR) with mention of 40mm GBR projectiles)

Comparison Of Aerodynamic Characteristics Of Live And Inert 70-mm T23I Gun-Boosted Rockets @ dtic.mil/dtic/tr/fulltext/u2/144336.pdf


There’s a chapter on GBRs in Dale Davis’s classic 1980s work Historical Development Summary of Automatic Cannon Calibre Ammunition 20-30 millimetre, covering US developments 1952-83 and published by the Air Force Armament Laboratory. However, this is primarily concerned with efforts to make a rocket-assisted projectile for the 30mm GAU-8/A. He also talks about the general issues around gun-fired rockets (not very positively) but doesn’t mention anything in 40mm.

Thanks for the comments!

Tony, I should have checked Dale’s book yesterday. Thanks for pointing it out. The 40mm is a Gun Boosted Rocket, not a Rocket Boosted Projectile. I believe the projectile is a folding fin rocket that fits into a tapered 40mm case.

Strange that Dale didn’t mention it since the report I have is pretty clear that the CAS Gun System Study Group that awarded the four gun system study contracts in early 1968 was staffed by Armament Lab personnel with the exception of the financial analysts who were provided by the Armament Development and Test Center. Dale could have been on the team or at least knew what was going on with the team. His comments on GBRs may be the reason the 40mm concept never went anywhere.

I truthfully do not remember who gave me this material, whether it was a Lab guy or one of the ADTC guys but it was from Eglin. No question Dale would have known the details of this weapon, but I suspect that the Lab was not directly involved in the testing or Dale would have the material that was passed to me.

The contract number-as best I can tell-indicates it was let in 1969 and was a Cost Plus contract which is typical for a study/technology development effort. Perhaps the contract was not let by the Armament Lab or by ADTC.

I do know that gun development was managed out of the A-X/A-10 program office at Wright Patterson AFB, not out of Eglin. They hired some of the military technical guys out of the Lab, and these guys returned to Eglin after their tour at WPAFB. The program manager for the gun was an “interesting” Colonel at WPAFB who was later the guy who accidentally blew up the Service Station in the DC area with his 30mm Anti-Tank Rifle! That is a story for someone else to tell.

Lots to do on this subject. Perhaps I should post on the BOCN. Are there other Forums where I should ask this question?

If anyone can suggest where I look on the internet, I’d appreciate it. Searching the internet is not my strong point!

My objective is a Seminar at SLICS next year if I can get enough info.


Does anyone have photos or specimens of the TRW 30mm and/or the Harvey Engineering 57mm Recoiless cartridges. I would also be interested in photos of the two guns. I checked Chinn’s Vol 5 and although he covers through 1989, he doesn’t cover neither the Harvey nor the TRW GAU-8 competitors nor does he address the 40mm.

Hi Lew, a brief report on this 40 mm weapon system was published in Aviation Week & Space Technology January 17, 1972 p. 42. The round is described as a solid-propellant rocket, with fins folded inside the case with only its nose protuding.

Fede, You are a jewel! This sounds like what I’m looking for. I have no idea how you found this but many thanks for everything!

Cheers & Thanks!

Fede, Thanks again. Below is the article from the Jan 1972 issue of Aviation Week & Space Technology. This is the round and I think this article explains why it was missing from Dale Davis’ book. it was developed by the USAF Rocket Propulsion Lab at Edwards Air Force Base CA, now the Edwards AFB Space Propulsion function of the Propulsion Directorate of the Air Force Research Laboratory headquartered at WPAFB OH. The Armament Lab at Eglin may have had a hand in developing the gun, but Dale Davis’ organization apparently had nothing to do with the ammunition, and from his comments in his book, he disapproved of the concept. Probably an interesting story there somewhere.

I have sent the film off to be put on DVDs and we will see if that yields any new information. The contract number led to a dead end. that contract was destroyed long ago.

Am still looking for any info/photos of the TRW 30mm GAU-8 contender and the Harvey 57mm Recoiless GAU-8 contender if anyone knows anything about them.