I had samples of these rock “drilling” rounds in my 2008 Rimless Groveless display at SLICS. This is what I had noted about the rounds, and was copied from various printed materials. The last paragraph covers the types displayed.
David Dardick, Tround International Inc. has developed, along with the help of Dresser Industries, a drill bit that fires ceramic bullets so as to pre-fracture, hard rock formations at the drill face, still allowing a somewhat conventional drill to work at the same time. Initial testing found this method to be from 200 to 400 percent faster through hard rock formations, and in side-by-side testing the Tround bit showed little wear when compared to the conventional bit. An added benefit is that seismic signal measurement is easily accomplished.
The prototype drill bit was loaded with 500 salvos, with the commercial bid holding 5000 salvos. Working on the open chamber principle, a sensor fires the gun when hard formations are encountered.
These are .25 Cal. Dardick Triplex Tround Rock drilling variations, and a 47.2 grain ceramic projectile. All show a 2-piece case, a copper primer in a copper washed steel battery cup, and three ceramic bullets. We assume the case color variations may pertain to a certain load strength, but are not sure.