A buddy and I went shooting tonight, and I let him use my 9mm (Kel-Tec PF9) for a while as I was shooting other guns. I didn't notice until after I'd shot a couple magazines that he'd adjusted the backsight (I'm left-handed, he's right-handed), and all of my shots kept going down and to the left of center mass despite where my frontsight was pointing. I didn't have time to adjust my backsight before we left the range so I'm not sure which way I need to adjust it to get it back the way it was, but if my shots are going to the left when I'm lining up my sights, should I move the backsight to the right to hit center? Is there a way I can tell if my shot will be centered without going to the range? I'd hate to have to use my gun in the interim and have my shot placement off because of my sights.