I have a pair of each grip frame (Old Model), and yes, they are pretty good at Lego snap in replacement. I recommend a new reduced power hammer spring while you're at it. On my Bisley's, I also have a modified part (Power's "Power Paw") to allow you to rotate the cylinder backwards when the gate is open for a quick 6th shot on the clock. My Bisley pair are Blue and 5.5" while my standard pair is 4" Stainless and completely stock. They are built like tanks and last forever' My Blue have 50K each and my stainless have 25+K rounds through them. Never had any stoppages in any of them!
Ivan