That gun was sort of purpose-built for the then-popular sport of PPC, the target game that developed out of Police Target training. It was shot on man/torso targets at 7 1/2, 15, 25 and 50 yards (or reduced targets for a second round at 25.) Hence the 4 position front sight. The heavy barrel with underlug was developed by Colt for the Python and was "perfected" by Smith. It aided in keeping the gun on target during the rapid fire needed for the event. My shooting partner had one and did quite well with it back then.

Froggie

PS This was a very popular event for a while, and custom gunsmiths built "Smolts" using Python barrels on Model 15s, or just put custom bull barrels on. There were all sorts of weighted underlugs, ribs with sights, slicked up hammers and triggers, etc, etc. Smith really read the market right that time, and introduced the 586/686 line for a stronger-than-Model 19 357 Mag, and were right in the perfect position to add the front sight and make your "factory custom" that could be used to compete right out of the box.