Do not confuse the 357 AR Max (rimless) with the 357 Max (rimmed) round.
The 357 AR Max is a wildcat and no one ever tried to limit it to 40,000 psi. I use brass made from 223/556 in an AR platform gun. The AOL for my stuff would be the same as the 350L for an AR (magazine limited). The crowd that worked this round up were willing to go to 55,000 psi or slightly higher.
I got a little over 2000 fps with a 200 gr in a 16" gun using Wc 680 in a load that was just a little too hot for the primers. I think I should be getting 1985 fps or so in a load that seemed Ok for the primers. I considered the 1985 fp "close enough".