The Speer Gold Dot .357 Magnum ammo is some of the best factory .357 self defense ammo out there.
The 135 grain Gold Dot bullet was designed by Speer for the NYPD's 2" .38 Special revolvers. The bullet reliably expands at the lower velocities achieved by short barrels.
By specially designing the jacket and the depth of the hollowpoint, Speer is able to get reliable expansion AND good penetration out of the bullet when fired from a short barrel. The bullets work well in guns from 2 to 4 inch barrels, but when driven faster from longer barrels, the bullet will fragment after expansion and actually penetrate less. The NYPD and LAPD have had excellent actual shooting results using the .38 Special load.
The .357 load is just a little bit more powerful. Actually a '.357 Lite.' Muzzle velocity is 990 feet per second from a short barrel. This is a great .357 load for short barrels because its easy on recoil, and has much less flash and blast. The bullet does what it is supposed to do and reliably expands AND penetrates. I use the GDSB loads in my 2" Model 60 and 3" 13 and 65's.
The 158 grain .357 Gold Dot is a great load for revolvers with 4" and longer barrels. Also works great in the 16 and 20" carbines. The bullet has a tougher jacket and penetrates deeper for penetration of light barriers or hunting. The 158 grain load has a muzzle velocity of 1,235 feet per second from a 4" barrel as tested by Speer. Velocity will be even more from a carbine. I use this load in my 4" 686 and my 20" Rossi carbine. Details are at the Speer website here:
Speer Ammo - Ballistics Tables
No, I don't work for Speer, I have just studied this ammo before I decided to trust my life to it.