I would HIGHLY recommend the Mossberg SA-20 Tactical, which is what I use for teaching our 4 day Tactical Shotgun classes. The Remington 1100 Is great too, But I prefer the SA-20. I load mine with #3 Buck.
I am an instructor at Frontsight, Nevada, and research has shown 20 Gauge to be superior to 12 Gauge for home defense, as well as overall versatility.
From Massad Ayoob:
For the person who wants only one all-around shotgun, I would respectfully suggest a gas-operated semiautomatic 20-gauge. Yes, you'll have to clean it more often, but if you live on a rural homestead, you're already accustomed to taking care of your equipment, and each time you disassemble the gun as per the clearly written factory manual, you'll become that much more familiar with it and, therefore, that much more comfortable with it.
The gas-operated semiautomatic is much softer kicking than any other shotgun type firing the same shell, for the simple reason that its gas-bleed mechanism that runs the firing cycle is diverting that much more impact away from the shooter's shoulder. If you haven't shot different types of shotguns of the same weight with the same shells, you really can't appreciate how much "kick" the gas-operated semiautomatic soaks up with every shot fired.
The standard 2¾" 20-gauge shell, not the more powerful 3" Magnum 20-gauge load that Francis Sell popularized, will send five-eighths of an ounce of lead out of the muzzle at 1400 to 1600 feet per second depending on the load and barrel length you've chosen. If you use a single rifled slug projectile, it will be about .62 caliber in diameter. That translates, basically, to shooting the target twice with a .44 Magnum in the exact same instant. Unless you have to shoot tiny pellets of steel instead of lead at a bird flying half a football field away, that's the kind of firepower that gets the job done.
There are lots of good semiautomatic shotguns out there, chambered for the 20-gauge. My personal favorite is the gas-operated Remington, in the 1100 and 11/87 model series. The standard models come with five-shell capacity, four in the magazine and one more in the firing chamber. They also come with magazine plugs to bring the gun down to the same capacity you would have with that neat little Benelli, one in the launch tube and two more in the magazine. But that's only required for waterfowl hunting, and as we've noted, that's the one downside to choosing a 20-gauge in the time of steel and bismuth shot pellets being required for hunting waterfowl. Google "Brownell's" and you'll find lots of accessories, including extended magazines.
If you're buying a "family shotgun," which might be fired by Dad or Mom, by young Sis or young Bro, I would most strongly urge you to order the shotgun with a "youth stock," designed to fit people of shorter stature with shorter arms. A shotgun with a long "pull," which refers to the distance from gun butt to trigger, will be fine for a tall person with long arms...the sort of person that most guns seem to be built for. With smaller folks, these dimensions require them to lean back to hold the overly-long firearm steady. This takes them off balance for swinging on a moving target like a flying supper-bird, and-most seriously-it makes the gun muzzle jump skyward with the recoil of every shot. This slows shot-to-shot time in delivering accurate hits. That's the difference between a deer getting away or being consigned to the family larder today... and it can be the difference between stopping the second of two home invaders before he can murder the loved one who had to access the shotgun or not.
It is no trick for the larger person to shoot the shorter-stocked shotgun. That person simply pulls it tight into the shoulder and brings their eye closer to the sights. A short-stocked shotgun equals a gun the whole family can use very effectively. A long-stocked shotgun equals a firearm that only the taller, longer-armed members of the household can use with maximum efficiency, especially in an emergency.
It's that simple.
Bottom line
The 20-gauge shotgun, particularly in the gas-operated semiautomatic version, seems to be one of the best-kept secrets in the firearms world. About the only thing it's not very good for anymore, since heavy lead shot was legally forbidden for waterfowl hunting, is the harvesting of high-flying ducks and geese. In big bear country, I might also prefer the bigger slugs of a 12-gauge.
The 20-gauge will always "kick" less than the 12, and it will handle better and faster on quick-moving upland birds. With a buckshot load, the standard 20-gauge shell will fire 20 pellets of #3 buckshot (approximately .25 caliber), which will penetrate to about the same depth at about the same pattern width as the standard 12-gauge "urban load" of #4 buckshot, which comprises 27 pellets (about .23 caliber). The wound paths will be about the same depth and width, and the only difference will be how finely the macerated tissue has been chopped by the projectile paths. "Only the Medical Examiner will know for sure," and then only when he counts the little lead balls recovered from the body, or the white dots on the X-ray of the corpse.
The 20-gauge shotgun. It is offered here for your consideration for the simple reason that it has compelling logic and a strong field history going for it.
