I too shoot a 338rum with a 300 gr. at 2975 fps with 93 grs. of Retumbo, out of a 30" Pac Nor three grove barrel.Never had any trouble being to hot at 1000 ft. or 90 degree weather.Easy to extract from chamber. I can tell you I shoot a 180 gr. BT at 3600 fps with no trouble ,and a 225 gr at 3300 fps. I use 4831 SC with a 180 and 225 gr. SST with H-1000. Tim