I like the 257 Roberts, currently have 10 of them, and think that it is a practical varmint and medium game cartridge if you load your own. When I got my first 257 Roberts, Winchester/Olin cataloged 257 Roberts factory ammo with 87, 100, and 117 grain bullets, so the guy who wasn't a handloader had a factory load option if he wanted to shoot varmints. Back then, the dual purpose capability of 0.243" and 0.257" bore rifles was a marketing strategy that firearms sellers were pushing hard.
I've shot a lot of 0.257" component bullets in the 75 thru 120 grain range over the past 50 years and settled on a few that have worked well for me.
75 grain VMax and Sierra HP
87 grain Speer HotCore and TNT
90 grain Sierra HPBT
100 grain BT and Partition
110 grain AB
115 grain Partition
120 grain Partition
I'm not a big monolith bullet guy, but the 80 grain Barnes TTSX looks like it would be a winner too, if you can live with the not so slick 0.316 BC.
6 of my 10 are short actions from Marlin, Remington x4, and Savage. The other 4 are long actions from Mauser x3 and Ruger. The Mausers are military actions, a large ring Venezuelan 24/30 made by FN, a small ring Mexican, and a small ring Swed made by Husqvarna.
