I have a 257 Improved/Ackley on a 98 action. Loaded standard 257 Roberts for years before I had it rechambered. Loves 100-120gr Sierra boatails for deer sized game, 75gr flat base for varmints. Varget is my go to for lighter stuff, IMR 4350 for heavy bullets (mainly because I have a lot of IMR 4350 cans around). Something to remember is that many 257 Roberts are older rifles, and tend to have more throat erosion/freebore. My biggest accuracy improvement was going max OAL, or longer, till the bullet was close to the rifling. Still my go to for when I get dragged out for deer or coyote hunts.