john,
I've been looking for a couple of years... have seen a few in that time, but most were priced too high for me, or they were in less than acceptable condition.
john,
Shooting .38+P/125gr vs 9mm/124gr loads (both standard pressure) from my 3" SP-101s reveals a barely noticeable increase in felt recoil for the 9mm... chronograph readings (sorry, I don't have them "on" me) are better for the 9mm, though not by a huge amount.
Moon clips do make for fast reloads, but also require a bit more care in handling than do the HKS speedloaders.
Overall, I enjoy shooting 9mm from my little SP-101, but it isn't so much better, that I'd entertain ridding myself of the .38. I haven't had the chance to shoot the Speed Six yet.
My other 3" SP-101, shooting .357 Magnum/125gr loads trumps 'em both, in terms of velocity, recoil and muzzle blast!