Big Z is absolutely correct. The faster the bullet is moving at impact, the faster it'll expand, and in the case of standard cup and lead core bullets, the more weight it'll tend to lose. The myth about faster cartridges causing a bullet to go through too fast to expand is a pervasive myth that just won't die, probably because too many ignorant folks repeat it over and over that it's almost gospel. I think that these folks might think that the rate of a bullets expansion is fixed relative to the target medium that it's passing through, such that the faster moving bullet won't have enough time to open up. But this ignores the fact that it is the bullets kinetic energy that causes expansion. The bullet that's moving faster hits tissue at a greater rate and with more force, causing the bullet to expand faster as a result. Because the bullet expands faster, it has enough time to expand in the same span of the animals body cavity, and will expand more because the of the greater force pushing against the nose of the bullet. One of the problems that plagued the early Nosler BT bullets was that some of the calibers and weights would expand just the right amount to achieve the right balance of expansion, weight retention and penetration. The problem was that the bullet that worked perfectly in, say, a 257 Roberts at SAAMI pressures would disintegrate violently and rapidly at 257 Weatherby velocities, causing a large but very shallow wound that may not reach deep enough to damage vitals. The 257 Weatherby will push a same weight bullet 600-700 fps faster than the 257 Bob, and the deer bullet became a varmint bullet. Nosler has since redesigned the hunting BT's to be tough enough to work properly at up to 3100 fps impact velocity.

Now that you've been properly informed, you won't be one of these poor folks spreading incorrect information out of ignorance.

Mike