Saw a scary round at a preserve in VT. Appears to be a 20 ga brass case necked to about .60. The preserve owner said a client shot a boar with a DR chambered for the round, which appeared to have a solid lathe turned bullet. Anybody know about this wildcat?? Nice to know somebody's crazier than I am.

Could be the 20/577
That's an over-100yr old cartridge, and quite effective!



Cheers
Tinker

Agree with above, 20/577 most likely.

from www.municion.org the 20/577 Alexander Henry c. 1895



Is this the one?

I just love this web site


Here is another one that is very similar: 577Rewa based on 600NE. I never heard or dont remember the 20/577 but the Rewa was famous attempt to get a little more powerful 577. If your Spanish is up to it, details at municion.org

So, Art's 577 Tyrannosaur is just a 20 Gauge 3"
with the .766" rim turned down to .691",
an extractor groove cut, and necked down from .615-cal to .585-cal.
Near same rim thickness, .048" versus .050".
I'll stick with the 20 Gauge 3.5" with 900-grainers at 2150 fps.
DRG says: "Kiss my liberal grits!"