Is this a question or statement?
So far as I know, the HD was never factory-chambered in .357 magnum, except for the experimental models leading up to the Registered Magnum.
The guns are stout as a locomotive, and can handle most of today's relatively mild magnum loads.
Back in the day, many, many many LEOs had their HD's rechambered/reamed to accommodate .357 ammunition.
That put 'em on a more even footing with the baddies.
Nice-looking gun, by the way!