[July 4th]

Would you mind telling me what firearms does cause rounds to tumble? I've only read about the what i called spinning..

It's not the firearm that causes the round to tumble. The .223 is just like any other rifle round where the rifling on the inside of the barrel causes the round to spin. The increased stability means longer range and better accuracy.

The round tumbles when it hits an object, the reason being a pocket of air left in the nose of the bullet. The nose collapses, the bullet destabilizes, and rips itself apart as it travels through an object.

[Freedom2specul8]

I had seen diagrams of the insides of barrels and was surprised to see the design. But forgive my terminology..I thought the inside of the barrel looked like a big spiral. Neways..I was obviously incorrect in it's purpose. Thank you for splaining.

[justlurking]

It's not the firearm that causes the round to tumble.

No, the firearm doesn't make the bullet tumble. But, it can be designed so that the bullet is more or less likely to tumble on impact.

The rifling can impart just enough spin to the bullet to keep it stabilized for a short flight, but tumble on impact. But, this results in decreased accuracy at longer ranges.

Conversely, A higher spin rate stabilizes the bullet for longer distances, but inhibits tumble on impact.

The round tumbles when it hits an object, the reason being a pocket of air left in the nose of the bullet. The nose collapses, the bullet destabilizes, and rips itself apart as it travels through an object.

You are describing fragmentation of a hollow-point bullet, not tumble. The later may happen as a consequence, but tumbling will occur even with a full-metal-jacket under the conditions I described above.