Buckle up y'all and learn from my expensive but lucky mistake. Long time shooter and consider myself very safe around firearms. (Don't we all.) Finally pulled the trigger and purchased a long-awaited 1911 in 45 auto. My first 45 but I've been shooting a 38 Super 1911 for 20 years. Picked up the new 1911 in November and have about 200 rounds through it. I'm retired LEO so I'm fortunate enough that my old agency allots some ammo for us each month. Headed off to the range yesterday and grabbed some of the 45 ammo...mostly. The ammo is in giant boxes about a foot square and 8 inches deep, filled with ammo. Three boxes, 45, 40 and 9 sitting about two feet apart. Bet most of you see where this is going. Set 15 rounds down range, smiling at my nice group. Next mag, first round, click. Well it's a new gun and pretty stiff still so I'm thinking I didn't seat the mag all the way or it didn't strip off the first round. I wait just in case of a hang fire, cautiously open the slide and see no round in the chamber. Drop the slide, touched off a round, well, you see where this is going. Very different sound when a 40 cal detonates in front of a 45. Guess I can say I've now shot an 85 magnum. The good part. No one was hurt. The remains of the 40 case is sticking out of my barrel and I presume 230 grains of copper and lead close behind. Slide is locked almost shut because the entire underside of the barrel is filleted open (after the armorer removed the spring so we could see under the barrel. Tell me this part doesn't hurt. Explaining this to my wife on the phone (I'm out of state at the moment) and she just went to a ladies only firearms class last night (which I told her to share with the instructors so others can learn). This morning we were talking about it and she told me how the instructors said if the gun doesn't fire to (do all the right things) including putting a zip tie or something down the barrel to make sure nothing is in there. Yes, yes dear, that is the correct thing to do. Many at the range were blaming the officers who throw extra ammo back into the wrong bins. True, they shouldn't. But ultimately it's on me. Should have noticed I was putting a 40 in the mag, not a 45. Should have cleared the malfunction properly. Have been training for the past 30 years to clear quickly and get back in the fight...which worked great...for 30 years. Monday will be a phone call to Remington (think this is covered by warrantee?) to see if it is salvageable or if I have a really cool, expensive paperweight reminding me that stupid hurts. The best mistakes to learn from can be ones made by someone else. Feel free all.