A friend had a bucket full of penetrators from the 168 gr AP .30-06 bullets. He had been testing penetration of these bullets which were available in quantity at the time by handloading in both .30-06 and 7.62 NATO. The Bullets were said to come from France and had two crimping cannelures to allow differing seating depths for the various .30 cartridges they might be used with.
He had used an old concrete foundation as a target and when the penetrators went through the jackets disintegrated leaving the undamaged penetrator clean as a whistle.
I'd considered using some of these to make an AP bullet for the .357 by swaging a length of copper tubing around the penetrator and sealing the base with a gas check.
The nose of the jacket would be open with a tubular body. On impact I figure that if it hit unprotected flesh the open nose would act as a tube cutter , if the nose were saw cut it might peel back in petals.
Velocity would have been fairly low with such a heavy bullet.
Of course I never got around to making these and mislaid the AP cores long ago.