"Printing" is when your concealed firearm is discernable by its outline. The gun itself isn't visible, but it's still obvious what the bulge is. It's a problem for all gun toters, you have to adapt your wardrobe to fit your concealment needs. There are some who can easily conceal a 45ACP in Commander size during the summer, I'm not one of them unless I wear something that covers it completely. The biggest thing I can conceal easily is a SW K-frame or something similar. Barrel length matters less than the size and shape of the butt, which is why I prefer round-butted Smith guns of all frame sizes.
Printing is never a good thing. Bad guys who know you're packing may avoid you, but they may also target you via ambush, to take you out of the action before you can react. It can also get you arrested, or at least horribly embarrassed. I remember responding to a "Man with a Gun" call one night, the poor guy was off-duty and stopped to pick up a gallon of milk from the top shelf at a local store. The clerk saw the gun and freaked. He alerted the manager, who called us 911. Four squad cars came screaming up as this guy walked out of the store, and we took him down in front of several people. It was pretty humiliating for him, especially when my Sergeant publicly chewed him out for being an idiot. If he's been dressed like a bum, we probably would have gone even harder on him. Sarge suggested that if he was gonna carry that openly, to keep his badge visible as well. Discretion is critical!
Papajohn