It’s most def beefier through the frame that a K gun; this Speedy will go into my JMCK “George” (@gjm) well enough to do in a pinch, but you can see the clamshell getting stretched a little, and it doesn’t “click in” like, say, my 4” M66-1 does.
I will absolutely be taking the speedy on the next hike, so K-popping kydex works, but this thing is heftier than a K. Leather compatibility—as would be period-appropriate—is no issue though. Also, I’m told that the HKS Colt MK3A speedloaders work better than the HKS 10A loaders. Of course, I’m now in a moonclip world, so I wouldn’t know.