Be careful of what you feed that 66. As you probably well know, 125 grain JHP 357 factory ammo gained a reputation for cracking forcing cones of K-frame guns due to the cut out where the crane fits under the barrel. I have placed an 1100 fps speed limit on ammo for my K-frames and frequently shoot 38 Specials out of them. L-frames were designed as full time 357s, but K-frames are part timers, primarily 38 Specials. I consider K-frame magnums to be true +P38s.