There's a reason most are acp: it makes a lot more sense. At the pressures a sane person would run in a S&W revolver, acp and Colt can be loaded with the same bullets to the same performance levels. Acp revolvers can be fired with or without moonclips, or with autorim ammo. The cartridges are smaller, easier to carry, more available, cheaper, and quicker to reload. The Colt has nostalgia going for it, but not much else.