Actually most of the gaulling that occures is between stainless on stainless. I'm not trying to say that stainless and reguler steel cant gaull if put together, just that its a lot more compatable if you have dis-similar materials. As for the compatability of stainless barrel/blue frame or vice versa, you can mix them up any way you like. I use them in both configurations. Just my $.02 Kn