257 Weatherby: 28" #5 fluted SS Lilja 3 groove barrel, moly coated 110 accubond, .015" off rifling.
Had to stop using 115 VLDs because rough throat combined with 3 groove began to damage VLDs causing poor groups with occasional flyers. Barrel throat looks horrible in borescope with severe cracking for over 5 inches past throat. The data below was obtained with this old barrel with over 750 rounds through it. Your results may vary. Much to my amazement it still shoots very tight groups but cleans up with much effort.
Original load 75.5 gr of RL-25 vel 3615 fps
there was no load data when RL-33 first showed up:
starting load 76 gr for vel of 3318
jumped to 80 gr 3432 fps
81 gr 3525
82 gr 3559
83 3625 which slightly faster than old load with RL-25
83.5 3674 fps shot well
84 gr 3704 fps shot well
84.5 gr 3735 slight signs of pressure on one case of four this is max case capacity with drop tube
mine gets a steady diet of 100 sierra fb spitzers and 7828. Id almost rather shoot a heavier bullet but the 100 seirra just outshoots everything in that gun by a good margin. Ive probably shot 15 deer with it using that bullet and ate every one of them so i guess it does the job. If i ever wanted to shoot something bigger i guess id look to a heavier load but then i have differnt guns to take care of those chores anyway. the 257 is about exclusivly used for deer shooting when i know the range might be 350 yards or more.
I shoot the 115 Ballistic tip over H-1000 215 primer. That bullet has never failed me and I drive it. Doesn't matter 50 yrds or 500yrds. As my friend once said 'that round makes 'em bleed from every orifice'.
LongRanger here on the site has some pretty good loads too.