Jeff, I've shot several 1,000 rounds through a .220 Swift and a .22/250 and generally I was pushing them for all the velocity I could squeek out of them. I NEVER had a bullet blow up in flight. I think you've been reading gun magazine stories by people who don't know what they are talking about. On the other hand, I have seen such bullets blow up on impact with some obstruction in their flight. I've shot at long range varmints only to see my bullet clip a mesquite branch near the target and explode in a gray puff. But they don't just fly apart on their own that I've ever seen.

To talk about penetration, perhaps we should consider what out tanks and other tank killer guns shoot today. Tanks shoot the small sabot round of very dense, very small diameter projectile going very fast. It's basically a giant .220 Swift and the sabot goes thru enemy armor like it's hot butter. If that doesn't work they can change to the shaped "HEAT" charge which burns it's way inside the tank.

There's no mystery here. Small size and lots of speed applied to very small area is what drills steel. Where 30 caliber AP ammo will impress you is when it's shot into something like a tree or sand. You'll dig a hole a couple feet deep to find an AP shot into sand.[:-]