Sounds like the 284 STAK which is a 300 Dakota ( a true 404 Jeffries case ), at 2.555, necked to 7mm and improved ( 40* w/ .012 taper )
The STAK will push the 180s over 3200fp
The 7mmRHB is a shortened RUM case, 2.555, 35* shoulder, .015 total taper. It holds 4 more grains of powder than the...