I was cleaning up yesterday and ran across a large bag of old .351 Winchester Ammo . I dug out a box of .357 Max ammo and yes they are pretty close except for case head, didn't mike them. But it looks like what we got in 100 years is 400 FPS more velocity from the .350 Legend with the 180 grain bullet !
The box for the .351 ammo reads 1700 FPS with 180 grain FMC ammo from the early 50s !
BTW the .350 Remington easily does 2100 FPS with 200 grain bullets and operates at 35000 psi from the factory. I shoot 180s close to 2500fps in handloads in my 18" barreled 600 Carbine which are probably 50,000 psi !