butlersrangers wrote on Feb 12^th, 2018 at 2:16am:

IIRC - Frankford Arsenal developed a rimmed, smokeless, .30 caliber cartridge that was used in some of the arms entered in the 1892 and 1893 trials. This evolved into the .30 U.S. Army cartridge. The possible trial Mauser rifle may be chambered for the .30 F.A. rimmed cartridge. The '.30-40 KRAG' marking is likely a much later hand-stamped addition. I believe some late trap-door rifles were used to test .30 caliber rimless experimental cartridges that became the .30-03 cartridge.

No, the .30 caliber TDs took a RIMMED round basically indistinguishible from what is now the .30-40 Krag. The rimless .30s were used in other trial arms of the period, such as (IIRC) the Durst. FWIW, our friend Joe Farmer has two (now perhaps 3?) of the Durst rifles, which are of two similar designs. The .30 TDs are well covered in my latest book.