The dog gave enough warning for you to get the kids into your bedroom and the shotgun out. Behind you, your spouse is calling 911 on the cell phone and holding a revolver. You're covering the top of the stairs as heavy boots clump towards the top floor..... What your shotgun is loaded with will be of less importance than skills, training, and tactics, but ammo does count. I field a couple queries each week, so this is of great interest to a large number of people. Here's my opinions and advice based on fact, not movies or wishful thinking.... First,some stuff to avoid. Less lethal stuff like rubber buckshot or tear gas loads. It's regarded as Use of Deadly Force even when the police do it, and they do it when backed up by cops with real ammo in their firearms. That's in case L/L doesn't work. There's a clue there. Use something more likely to STOP someone when that is desperately needed. Also, avoid anything with a name like "Ultimate Deathmaster" or skulls on the box. Don't laugh,it happens and PT Barnum was right, one IS born every minute. Anything exotic like Dragon's Breath, bird bombs, buckshot strung together on a wire,etc.10 thin dimes would also be a bad idea. So would be reloads. Any shooting, justified or not, will be scrutinized under a microscope by LE folks who are not necessarily your friends. There is a case for and against using birdshot. Sometimes it works well. Usually that's at extremely close range where the wad still contains the shot,acting like a giant Glaser Safety Slug. Sometimes it creates ghastly but shallow wounds. Since STOPPING the threat usually involves disrupting the Central Nervous System grossly, these shallow wounds do not suffice. Bigger pellets penetrate farther. The common name for big pellets is buckshot, from its use in deer hunting. Common US sizes are 000 ( about .36 caliber), 00 (.33), 1 (.30), and so on. 4 buck(.24) is the smallest. The largest buckshot that fits in a 20 gauge is 2 buck, but 3 is more available. 1 buck is the biggest for 16 gauge. 00 is the choice for most police agencies and lots of us civilians. 8 or 9 00 pellets at a reasonable muzzle velocity has plenty of energy to transfer and a lot of frontal surface to help that happen. Even three to five 00 or 000 pellets can make the miniscule 410 into an effective close range tool. 00 also patterns tighter than the smaller stuff, all else equal. And that brings up another point. Some folks like spread, thinking it can make up for bad aim under stressful conditions. Others, including me, prefer a small pattern putting ALL that energy into the right place. Forensic experts tell me that the most effective load will have all the pellets in 5-8 inches. Of course, the biggest pellet is one bore sized chunk of lead, usually called a "Slug". These have some use for defense but not inside. If they are designed to penetrate a deer broadside and exit, they can pose a threat of overpenetration inside a building. Few of us are that rural that an errant slug poses no threat to anyone. Buckshot will also penetrate drywall and similar materials, but less so. It behooves us to become adept wiith our defensive tools until we can place that load where it needs to be in a very short time frame and do so without endangering innocents. Questions, comments, rants?