RE: 7x57 Mauser
good question. I assume you are working on a hunting load. The 139 hornady groups better in my CZ 1/2 inch. The 140 combined technology groups better in my Steyr >1/2 inch. I'm convinced the IMR 4064 is top dog for powder. Shot a WT buck and a doe this year with the combined technology...the buck at 90 yards and the doe at 325....both one shot kills...big buck walked about 20 yards and collapsed dead, doe fell in a heap...never quivered. I've had similar results with the Hornady SST's. Recommend you try both bullets and pick the best one. Good luck, Rick.