2.8 grains of Bullseye or 2.5 grains of WST under a 158-gr LSWC. In a 686, I would load in .357 Magnum brass and bump up the load very slightly.

.357-diameter is usually listed for "match" chambers and barrels.

I've used the .357-diameter swaged LSWCs from Magnus, and didn't have a problem. Magnus bullets aren't any softer than any other swaged bullet.

Tbh, while they were very good, unless you were shooting 25/50-yard DR matches, I don't think you'll notice a difference.