ldp4570,
1350 fps is a high velocity for a 158gr bullet but Grizzly Ammo will push a 180gr bullet to the same speeds. (I have no financial interest in the company, just trying to help)

The hottest 357 ammo I have is the Georgia Arms Deerstopper round. I'm sure the Double Tap, Grizzly and Buffalo Bore stuff is on the stout end, but Cor-Bon use to make super hot-loaded 357 Mag ammo that could only be fired in the Freedom Arms 353.

The Original O.P. didn't post the claimed velocity (Bbl. Len.?) for the Buff Bore 200 gr.ers.

Probably not the hottest but hot enough for me is some I have from Reeds Ammunition & Research Oklahoma CIty OK. There's a Online Store Anyway, it is

.357 Mag. 180 gr. Hornady XTP JHP @ 1,400 FPS/6" Bbl.

Randall

Well, I went back and checked the velocity after looking at the boxes of the stuff I've got - 3 of the 4 loads state a velocity so from the website:
http://shop.reedsammo.com/category.sc?categoryId=39

.357 Mag
125 gr. Hornady XTP JHP@1685 FPS(6" Bbl.)
140 gr. Hornady XTP JHP@1,529 FPS6' Bbl)
158 gr. Hornady XTP JHP@1,470 FPS(6"Bbl)
180 gr. Hornady XTP JHP@1,296 FPS(6" Bbl)

and one I don't have (yet)

200 gr. LH Hardcast Flat Nose Gas CHecked
1,300 FPS - 6" Bbl.

FWIW - I have a S&W 686P 4" Bbl. & haven't tried the 180 gr. yet, of the 125, 140 and 158 gr. loads I like the 140 gr. I just don't shoot it enough Most range sessions I take my .45s
SW1911 and 625 5" .45 ACP/Auto Rim

Randall