30mm Folded Ammunition

A fellow collector sent these photos of a 30mm folded cartridge, any information would be most appreciated.

Side view-

30mm FOLDED (3)

Top view-

Base view-

30mm FOLDED (5)


1 Like

From a forthcoming publication:

7.4 Folded Ammunition

This was a project to minimise the length of the gun action by making the ammunition as short as possible, achieved by locating the propellant in a container next to the projectile, with a channel from the base of the propellant chamber across to the base of the projectile. The inventor of the concept was Andrew Grandy, working at the Frankford Arsenal in the early 1970s. He was primarily interested in 5.56 mm applications but Folded Ammunition was made in a wide range of calibres up to 40 mm.

As the propellant burns, the gas passes through the channel before reaching the base of the projectile, in theory permitting more complete combustion. In the 30 mm example examined, the primer pocket is midway between the projectile and the propellant container, on the channel between them. Combustion therefore begins with the propellant which is closest to the projectile, rather than at the other end of it as with a conventional round.

An advantage Folded Ammunition has compared with Cased Telescoped is that the projectile is positioned in the correct place in the chamber before firing, like a conventional round, so that it does not have to “jump” from the cartridge case to the barrel. The gun used a push-rod to extract the cartridge case instead of a conventional extractor, thereby eliminating potential extractor breakages.

In the 30 mm version, the goal was to launch a 324 g projectile at 1,100 m/s with a peak chamber pressure of just 380 MPa. Honeywell developed the ammunition and ARES the gun system. A comparison with the 30 x 173 GAU-8/A round showed the following reductions: length 41%, volume 24% and weight 12%. The shape of the case evolved during development, with a folded version of the 30 mm WECOM being further reduced in volume by giving the propellant container a crescent-shaped rather than circular cross-section and partly wrapping it around the projectile.

The configuration of the cartridge facilitated the development of a recoilless variant, as recoil-balancing gas could be allowed to escape rearwards directly from the propellant container, and the percentages of the gas used for propelling the projectile and balancing the recoil could be adjusted by varying the size and shape of the channel.


Hi Brian,

This 30mm is from the folded system tests at GAU-8 ballistic level from 1974. I have seen other examples loaded with HEI-T and HEAT projectiles.

Picture of the test gun and test cartridge:




HEAT really? a 30mm shaped charge?? thats sounds really cool

Not that new, Germany made those in WW2 already. And in 20mm too I think.

The germans had tested it i know that but never thought anyone went on with it as it doesnt really have much penetrating capability at all

Thanks for sharing, I don’t remember seeing one before.

The US 30x113B M789 for the M230 of the AH-64 is using “HEDP”, i.e. HEAT-Frag.

Some other countries also tested stuff like that and the smallest HEAT I have ever heard of was in 7.62mm.

1 Like

A couple of additional photos sent to me showing the 30mm WECOM (U.S. Army WEAPONS COMMAND) experimental folded cartridge (also mentioned above by Tony Williams).

30 mm WECOM FOLDED, side

In the base view photo above you can barely see the numeral " 1 " towards the bottom center of the cartridge base.

Below is a comparison photo from Frankford Arsenal showing regular 30mm WECOM rounds positioned behind folded 30mm WECOM rounds.

Thanks Brian for reminding me of that group photo. Sadly, I’ve never seen one in real life.