What is it?

This item appeared in Magnum magazine from South Africa. It looks to me to be some sort of “tround” but with three projectiles? Any answers will be appreciated.

That is a rock drilling tround. There have been several discussions on this and trounds in general here on the Forum and a basic search should help you find them. I think there was also pictures of the drill head that fired these posted a while back.


THANKS, DaveE and bdgreen for the very rapid reply. I’ve passed this information along to the magazine editor. South Africa has a good deal of mining activity so it’s not too surprising such an item might be found in that country.

This is a very nice hard-rock-drilling Tround triplex cartridge. The three projectiles, loaded at a slight angle from each other to increase the impact area, are contained in separate sabots and are made of a ceramic material. When a projectile strikes rock, it fractures the rock, disintegrates, and is swept away with the rest of the crushed rock by the drill head. The firing of the projectiles is very slightly staggered to create a ripple effect for the resulting shock wave.

Most of these are a gray or black combination of colors and are not very rare. They should be, considering how few were made. If you go to GunBroker.com and search for “Tround,” you’ll see an auction lot for a set of four of these, with a starting bid of $59.99 and a buy it now price of $99.99. The seller has a fairly good supply, apparently having bought up all remaining stock. If you have an interest, I’d get a set now while you can. Other color combinations are in fact rare, like the clear one shown.

Here’s a section of one that Paul Smith did for my Tround book, together with about 20 more different Trounds.


Any idea when the book will be available?

Thanks for this. I’ll pass it on to the original requester. Very interesting stuff!

Mel, great cutaway!
And as you are on it, do these drilling cartridges have a caliber designation?

EOD and Zac,

Will probably introduce the book at SLICS '21. I know; it’s a long time, but these things just take forever. Maybe sooner.

The ceramic projos mike at 0.2405 In./6.16mm, with an OAL of 1.2370 inch/ 31.44 mm. So I’d call it a .24-cal, Dardick rock-drilling triplex.

Mel, thanks!

Just for my understanding, these things which appear like sabots (look semi-translucent) stay in the case then?

EOD, No, they (the polyethylene sabots) are there to protect the bore of the three separate barrels that protrude between the three rotating drill bits in the head, and they are expelled (fired) with the ceramic projectiles like most sabots. If you look at the sectioned round pic, you’ll see the black plastic pusher plate that propels the three projos forward. Here’s a grainy pic of the drill head showing the gun barrels. You can clearly see one on the right, the front of another on the left, barely visible, and the third is hidden between the top two bits.

Mel, thanks. Interesting image of the drill head.

So these are saboted projectiles. Means the caliber should be given over the sabot diameter then or?
Can you tell?

First I need to say “oops.” I was mistaken when I mentioned a pusher plate loaded behind the three sabots/projos. I was looking at the pic of the sectioned round, not the round itself, and thought I saw something that was not there. There is no pusher plate, which makes sense because that would have added another piece of plastic debris to be dealt with. There’s just an air gap in front of the propellant.

The sabot has an outside diameter of 0.3135 in/7.96mm and the base of the sabot has a 0.086 in/2.19mm hole in its center. The ceramic projo is very tight in the sabot. I can’t get it out, and I think the hole is simply a way for air inside the sabot to escape as the projo is being inserted into the sabot.

So far, I haven’t found an official Dardick designation for the round, but I’m still looking.

Mel, thanks!
So is it possible that with the 7.96mm the basic design is a 7.62mm/.30?

Yes, I’d agree with that designation since that’s the bore diameter.

I have a friend who sells drilling equipment of all types. I will ask him if he is familiar with trounds.

The ceramic appears “molded” or extruded as a rod maybe, cut to length, then ground to finish diameter.
The brown ceramic may be the prototypes, later the white.
The rounded nose may be prototypes, later the pointed.

Brown ceramic is 0.246" in diameter, 1.235" in length.
White ceramic with round nose is 0.245" diameter, 1.240" in length.
White ceramic with pointed nose is 0.242" in diameter, 1.230" in length (dirty white, maybe from the grinding) - the grinding is not uniform in these projectiles.

Sabot is 0.310" at the base and 0.315" at the mouth, length is 1.285" and there is a hole in the base.


That drill looks like an oil drilling rig.
I’ll have to read up on why the projectiles are canted outward.
Looking forward to the book. Understand it takes time.
Thanks for sharing

OK, Dave; here’s the “CliffsNotes” version. Well drill bits are very expensive and anything (within reason) that can be done to extend their life or enable them to drill deeper and faster is a benefit. Drilling through soft rock is easy, and the Dardick hard-rock drilling system has no advantage. A discussion of what is “soft” rock and what is “hard” will be covered in the book. However, when a drill bit is pressed against solid hard rock, e.g., taconite, the drilling process slows down, and the bit wears out relatively (compared to soft rock) quickly. When the drilling depth slows or no longer increases, as noted by the drilling rig operator, the bit must be changed. This involves pulling the entire stack of pipes out of the hole to get to the bottom one with the drill bit to be changed, a time-consuming and expensive process.

With the Dardick system, when, and only when, the drill bit encounters hard rock, the Tround Blast Hole Drilling System fires salvos of 3 ceramic projos to fracture the hard rock (striking it at velocities greater than 4,500 fps in a staggered ripple) in front of the drill bit, essentially turning it into soft rock, thereby increasing drill bit life and speed. This is what Dardick Tround hard-rock-drilling Triplex cartridges do and why they are interesting to cartridge collectors. I currently have 11 different variations of these to be covered in the book and am looking for more. Do you have any for sale?ole Drilling System