103 rows · the ultimate reloading manual. /. 257 weatherby magnum loads reloading data with 51 loads. the stoutest. 257 load is the 100 grain barnes tsx at 3570fps. This is a good muzzle velocity for the barnes because at lower impact velocities of 3100fps and below, this. refer to the current speer® reloading manual for handloading instructions. Be thoroughly familiar with those instructions before using these loads. manufacturer loading data list of cartridges by powder; Web. 257 weatherby magnum (hodgdon data) warning! load data for. 257 weatherby magnum. 100 gr tsx (barnes) diameter: Imr 7828 ssc (improved military rifle) starting powder: charge velocity charge velocity load powder (grains) (fps) (grains) (fps) density (%) imr 4831 65. 5 3589 69. 5 3858 93 supreme 780 67. 5 3527 71. 5 3812 87 xmr 3100 66. 5.
