I have 4 rifles chambered in 257 Roberts; three are Remingtons on short actions, and a Ruger 77 long action.
I shoot 100 grain Partitions exclusively in the Ruger, and the light weight bullets in the 3 Rem's. There are SO MANY outstanding 85 to 90 grain, 25 caliber bullets, I have trouble picking just one load that shoots well. The two 87 grain Speer's, the Sierra 90 gn HPBT, and IIRC, the Sierra 85 gn HP are 3 shot, 1/2" groups loads, occasionally shooting a 3/8" group.
I'm into quarterbores as my Step Dad had a 257 built immediately after returing from WW II.