I'd be careful using Berry's bullets for hot magnum loads. They don't recommend pushing them very hard, and you mentioned maxing out loads in your other posts. I don't know the minimum velocity needed to cycle a .357 DE but I imagine it borders on the limits Berrys outlines. (I've shot 1000's of Berry's plated bullets in .45, .44, and .357 but at below 1100fps.)
I'm using Sierra FMJ flat points in my .44 DE with Accurate Arms #7. Accurate has specific .44 loads for the Desert Eagle listed on their site, unfortunately they don't seem to have the same thing for .357....
From Berry's site:
*How do I load Berry's Preferred Plated Bullets?
Plated bullets occupy a position between cast bullets and jacketed bullets. They are soft lead, but have a hard outer shell on them. When loading plated bullets we have found best results using low- to mid-range jacketed data in the load manual. You must use data for a bullet that has the same weight and profile as the one you are loading. Do not exceed mid-range loads. Do not use magnum loads.
*How fast can I shoot these bullets?
Velocities depend on the caliber, but as a rule of thumb, we recommend you don't shoot our plated bullets over 1200 feet-per-second. Our 44's actually shoot best around 1150 fps. 45's are generally good at 850-900 fps. Our bullets are not recommended for magnum velocities.