I've found that around 1600+ impact velocities virtually anything with good tin content will mushroom. There is actually a world of difference between > 1600 and <1400. I did a lot of testing last year with 357 magnum carbines and cast bullets and fully convinced myself that big bore solids are the way to go.
You can get a mushroom that's all nice and pretty but will it go through? The more mushrooming the shallower the penetration. They are inversely related. You cannot learn this from water jugs. Which is why most people don't even think about it. Calibrated gel sobers you up quickly.
Finding balance is difficult and I observed performance windows of only a couple hundred FPS. This is fine with handguns but not acceptable in rifles.
Solids are very predictable. They always pass through and don't require nearly the power to perform. If the bore is big enough it makes at least that sized hole. Typically 30 caliber bullets mushroom to about 45-50 caliber. So 30-30/30-06 etc with cast is really about equivalent to 44 special/45 colt with a standard weight slug. Keith was right.
Jackets sort of change a lot with terminal performance. They allow the use of much softer cores that mushroom at even lower impact velocities. The jackets arrest mushrooming at a certain diameter so the bullet can achieve sufficient penetration across a wide range of impact velocities.