Have rarely carried my 4" GP as a CCW due to size and weight--the old Security/Speed/Service Sixes being much more comfortable for the same payload.
I have a Bianchi UM-84R holster, which is the revolver counterpart of the current GI issue synthetic flap holster, though, and like it a lot for field use. It carries that big gun very comfortably, protects it well, and is out of the way. Not cheap, but for knocking around outdoors it suits the gun nicely.