I just read that an M4 firing on full auto with a Knight's sound suppressor attached would generate enough heat and back pressure to cause the rifling on the barrel to go away after about 100 rounds.  Now without a suppressor, and firing semiautomatic.=, could the rifling disappear with heavy use?  Say I shot 150 rounds continuously without stopping, except for mag changes, as fast as i could pull the trigger?  Would this do it?  if not, how many continuous rounds would be necessary?  Or would the rifling never go away unless a sound suppressor is used?

I just read that an M4 firing on full auto with a Knight's sound suppressor attached would generate enough heat and back pressure to cause the rifling on the barrel to go away after about 100 rounds.

That is utter BS.

Now without a suppressor, and firing semiautomatic.=, could the rifling disappear with heavy use?

Your barrel would be shot out long before the rifling eroded to the point it 'disappeared'. Even to reach that point, we're talking in the neighborhood of 20,000 rounds for a chrome-lined military barrel.

Say I shot 150 rounds continuously without stopping, except for mag changes, as fast as i could pull the trigger? Would this do it? if not, how many continuous rounds would be necessary? Or would the rifling never go away unless a sound suppressor is used

The rifling doesn't go away. What happens is that supressors and rapid firing increase the heat and pressure in the chamber. Over time, this causes 'heat checking' (imagine the cracks in a bed of dried up mud in the sun - this is what the throat of your barrel looks like) in the throat of the barrel and accuracy suffers.

Here is a much more informative link on the subject from the late Gale McMillan, who definitely knows barrels.

yarchive.net/gun/barrel/wear.html