Owner of Buffalo Bore Tim Sundles on Buffalo Bore Heavy 357 Magnum Ammunition:
For those wanting/needing a lead-free, HEAVY 357 Magnum load, generating full power plus, here it is.
Below are real world velocities taken from my personal stock guns. The industry established use of long laboratory test barrels that give false high velocity readings is essentially misleading to the public who won't be firing the ammo from a laboratory test barrel in the real world, where it matters.
You'll notice the newer S&W 4 inch Mt. Gun, gave higher velocities than the older 5 inch mod 27 S&W. This is because of different internal barrel dynamics and chamber dimensions of the newer gun. In general, the newer S&W revolvers are made to tighter tolerances than those of 30+ years ago.
Due to the long-for-weight all copper bullet, the 357 does not have the case capacity to use a bulky flash retarded powder and thus there is a noticeable muzzle flash with this load in all the test revolvers, however the rifle shows no flash at all due to its longer barrel.
This load is the typical barn-burning, turbo charged, Buffalo Bore type HEAVY 357 Mag. load and as such, should only be used in revolvers made of all steel. It should not be fired in light weight, alloy framed or cylindered revolvers. Feel free to use it in ANY/ALL 357 mag. chambered rifles and all steel revolvers/handguns.