The configuration you describe is refered to as an AB (A weight barrel and beavertail forearm). This was one of the common rifles produced in the first few years of production, then it was dropped until reappearing again in about 1980. It lasted 4 or 5 years this time and was produced in 223, 243, 270, 7x57 and 30-06. It was resurrected once again a few years ago as a special run for Lipseys in 25-06 (with a 24" barrel), and was cataloged for a short time in 204 Ruger with the typical 22 inch barrel. As far as I know, there were never any in 257 Roberts.