how fast they blow up
how fast is related not only to speed but twist rate as well. Slower twist can shoot them faster with less chance of blowing them up. In a 12 twist at 4,000 fps the bullets spin at 240,000 rpm. In 9.125 twist they are spinning 315,616 rpm. It's the rpm that blows them up. Varmint Al did calculations on the Nosler Balistic Tips that showed you could hit about 420,000 rpm before they start to fail. Well over 5,000 fps in factory twists but in a 7 twist 4,000 fps is close.