Benjamin 392 brass question

My 392 and 1377 also have very light rifling. They just drag the button through to score the inside. Much more pressure and the soft brass would deform. My steel barreled springer is much more defined. I don't see any color variation, but I wouldn't sweat it. I doubt they get their brass from someone who mixes their alloys like chocolate and vanilla pudding. If you are seeing discoloration, I agree it's likely from the solder process.