Don't yell at me too much.
One BIG reason why your swpeedloader doesn't fit, is the left side grip has not been machined low enough to allow total clearance.
The S/L may get to the cylinder, but getting it back out, catches on the grip panel.
So, as a fast fix, either TUFFSTRIPS or Bianchi speed strips will work just fine.
How do I know this? I own a Taurus 850CIA (642-ish), and the factory grip is not cut down on one corner, catching any S/L I use. So, I use speed strips.
NOT MAXFIRE Loaders, please. You have a nice, new snubby. You don't want to stress the crane assembly.