So, we're talking about the bore. Exactly what is it that some lead or powder residue in the barrel is going to do to your gun? Is it a moving part? No. Is it going to clog the barrel and "Jam" a bullet? No. Is it going to change the ballistics of the shot at 30 feet from a dead center chest shot to totally missing the bad guy? Hardly. There's no rationalizing this. If you like to take a brush, solvent, and pads down the barrel of your each after you're done shooting, then have a nut. Nothing wrong with that. As some have said, it's got medicinal therapy if nothing else. But if you choose to blow out, use gun scrub, clean the mechanical parts of your gun and a quick lube before putting them away, then that too is perfectly fine. The barrel/bore itself will have no effect on whether the gun goes "BANG" when you need it to.