"Just took my 3530 out this weekend, first time to shoot. I had already found that it takes HK speed loaders just like the Ruger GP-100. Compared to my Rugers (GP-100 and SP-101) the Alfa was both more accurate and easier to shoot in .357. I had feared I would need a grip filler, but it turned out not to be an issue for comfort or accuracy. I was also concerned about the trigger locking up if you fail to let it return all the forward after a shot; that turned out to be a non-issue for range work. I'm still concerned about the trigger in a rapid fire self defense scenario. The gun is definitely a keeper, and I was very impressed with its accuracy. "
Found this review claiming that HK loaders work. I cannot confirm it from personal experience.....yet.
Edit: just glancing around Wolverine's site, they show the same loader for the GP100 and the 686, so if this guy isn't full of it ^^^, the S&W loaders should work. Maybe.