EDIT: and my anticipation is once more wrong as Mel is proving below!
My understanding was that the cases just get ground and expelled with the pieces of rock.


Jack; Yes, that was my post and I’m happy to say that I now have some correct projectiles for the 20mm Trounds: a PGU-27, PGU-28, and Phalanx. Thanks for the contact.

Falcon; The magazine for the Terra-Drill Trounds had a spiral shape that wrapped around the inside of the system’s long container/pipe. As the gun fired - three ceramic projectiles in each round went into three separate barrels - the empty cases went into another spiral magazine in the center of the assembly. I have excellent pictures of this setup and they will be in the book. The gun’s rate of fire was very slow, not at all what we might think of with so many other Dardick guns with extremely high rates of fire. As the drill bit ran into hard rock, the gun began firing maybe one round in four or five seconds to fragment the rock and allow the drill bit to move ahead at a higher rate then it could without the pre-fragmenting. Then, if the drill got through the hard rock and back into softer material, the gun stopped firing. Even though the drill bit was able to last a lot longer with the Trounds, it did wear out, and the entire stack was pulled out, the drill bit changed, the magazine of fired cases emptied, and the magazine of live rounds filled.

The Terra-Drill was very complicated and very expensive. Working the bugs out of it was a challenge that Dardick didn’t meet. Company finances were also a factor in the system not being perfected and adopted, but that’s another story.


The label on my rock drilling dummy. Which otherwise appears identical to the example Mel shows, (except the cracks are slightly different}.

Forgot I had this one too, different label and seems to use an inerted shot gun shell type primer.

The bullet in my display is 0.2430" in dia. & 1.2350" long. Weight is 47.3 grains (today)


Thanks for the very detailed reply. I also had the same thoughts as EOD.


Pete; Just curious. How did you measure and weigh your projectiles? I assume you removed them from the Tround case. Did you weigh them with or without the clear sabot? As I mentioned, some of the Tround’s ceramic “bullets” are of different lengths and weights, and some have a brownish color.


Mel, it’s just the bullet not removed from anything, just the way it came to me. From ???
See the above photo of the display it’s to the right of the three loaded rounds & left of the Cal. .50.
Dillon electronic scale & digital calipers


Mel, you are most welcome!
While I may not know the answer, I ususally know someone who does…
… Hopefully!



a display at SLICS 2007 I think


VERY nice!

Might you please expound upon your cartridges numbered 131 to 137?
I have seen photos of [one of?] those in the past, but have no knowledge of them.
Thank you.


Not Dardick but folded ammunition For more on these see H.W.S. Vol. III.

Here’s the text.

131-132 A .50 Cal. OMEGA Ball (XM1) by Philadelphia Ordnance for the .50 Cal. Omega Automatic Weapon System, using a 709 gr. M2 bullet.
The object of this system was to produce a weapon giving the ballistic equivalent of a standard .50 Cal. M 2 round but recoilless! This recoilless system was then to be adopted to a shoulder fired rifle not weighting more than 20 pounds.
This, and the following folded cartridges are from a design patented by Andrew J. Grady, Dec. 31, 1974 under U.S. patent number 3,857,339. Our display covers only a small sample of the variations (3 bulleted examples exist), and calibers (up to 30 mm) to be found. #131 Headstamped ” PO 8 82 024 ”, with a standard brass primer, a red annulus, a 2-piece case of 6061 aluminum holding 175 gr. of WC 860, or equivalent. powder. This, and others, were dated (Aug, 1982), and serial numbered (024) for ballistic tests. #132 Stamped on the inert copper primer “ PO 8 82 “, this (Aug. 1982) dummy is machined out of nylon, delrin or PVC according to the sales ‘brochure’, and were to be used in testing feed systems.

133 Headstamped “ GTG 1981 “ with white letter filling, this 5.56 mm G.T.G. folded XM-1 has a blue, glass filled, injection molded nylon case, a brass primer, and a gilding metal clad steel jacketed bullet with a red tip. Likely an inert example, but we are not sure.
These (and our #134) were primarily used for a single shot application, with thoughts to possible use in the sporting market, using a pre-packaged cluster of folded cartridges.
G.T.G. (Grand Technologies Group Inc.), was perhaps associated with Philadelphia Ordnance.

134 An inert sample set issued in 1984 by the ICCA, predecessor to the IAA. It uses the 5.56 mm G.T.G. folded XM-2 case, which was of; “super tough nylon, injection molded with the addition of primer pocket supports”.

135 Unmarked, this circa 1976, 5.56 mm folded impact extruded, 2-piece steel case has an AR-2, 37 grain magnetic cored gilding metal jacketed bullet, and a nickel primer. It is said there were 1000 of these rounds manufactured for test firing, and as handouts.
Resulting from an early 1970’s study, by Frankford Arsenal / Ballistic Research Laboratories (at Aberdeen Proving Ground), about the long range capability of 5.56 mm weapons, this FABRL AR-2 bullet was found to be the optimal design.

136 Serial numbered “5” in three places, this 5.56mm folded “lifetime” re-useable steel case uses a screw to secure the base and body together. It has a brass primer, and a gilding metal jacketed bullet. Made by G.T.G. it is said a total of 50 rounds were manufactured for use in a modified Sterling Arms single shot pistol, to be used in the Silhouette shooting game.

137 A Frankford Arsenal experimental blue anodized cast aluminum cased 5.56mm Encapsulated or folded example. It has a brass primer,` and a 55 grain gilding metal jacketed bullet. It is said 200 of these were manufactured for handouts to visiting technical personnel.


Thanks, Pete, way cool, and much appreciated.
I will have to check into the OAWS “recoiless” part of that!