So my dad has a 300 win mag browning BAR, book has the max at 74 gr coming out at 3148 fps for a 165 gr sierra HPBT bullet. Chrono has it at 3125 fps. All good. I have a 338 win mag browning BAR, book has the max at 68.5 gr coming out at 3000 fps for a 185 barnes XXX bullet. Chrono has it at 2700 fps. Way off. 10% off. Both rounds are loaded until the primers start to flatten. Any suggestions? I think it has something to do with the bullet profiles. Seems the Barnes X bullet comes out slower than the equivalent lead based HPBT. Edit to add, Rifles are identical other than bore diameter.