I have some "rookie" questions. I figure this has been addressed before so if you want to direct me to other postings feel free. First I want to get a pump for home defense and at this point will either get the Mossburg 500 or the Remington 870. Someone told me that one of these is better than the other in terms of where the trigger lock(or something) is in terms of ease of use for a right or left handed person. Also, regarding recoil in case my little wife needed to use it. Is the 12 that much more intense(felt recoil) than the 20 gauge. Also can you mount any of the available tactical lights on the 20 if I wanted to do that? Hang in their folks. One more. It seems that both the 500 and 870 come in a few variations within that model number. Anything that stands out as a preference? Thanks for all the help.
20 gauge/12gauge etc...??
- Thread starter nelso
- Start date
Spotted Owl
New member
I wouldn't worry about recoil. In a home defense situation you're going to be so pumped with adrenaline that you won't even notice recoil.
Ohio Annie
New member
I have a Mossberg .410 for this. 3 inch #4 shot shells.
Sissily,
Sissily,
rwilson452
New member
Which shotgun?
IMNSHO.
The only dumb or rookie question is the one you didn't ask.
I have some "rookie" questions. I figure this has been addressed before so if you want to direct me to other postings feel free. First I want to get a pump for home defense and at this point will either get the Mossburg 500 or the Remington 870. Someone told me that one of these is better than the other in terms of where the trigger lock(or something) is in terms of ease of use for a right or left handed person.
The Safety. on the mossburg it will work equally righty or lefty
Also, regarding recoil in case my little wife needed to use it. Is the 12 that much more intense(felt recoil) than the 20 gauge.
Yes the 12 will have more recoil but unless you intend to shoot the bad guy 25 times or so it shouldn't be a problem. More than likely if push comes to shove when you work the action within ear shot of the bad guy he/she will go bye-bye pronto.
Also can you mount any of the available tactical lights on the 20 if I wanted to do that? Hang in their folks. One more. It seems that both the 500 and 870 come in a few variations within that model number. Anything that stands out as a preference?
Get one with sights like a rifle. and a 20" or less barrel.
Most of the "Law Enforcement" models will handle all sorts of attachments
IMNSHO.
The only dumb or rookie question is the one you didn't ask.
I have some "rookie" questions. I figure this has been addressed before so if you want to direct me to other postings feel free. First I want to get a pump for home defense and at this point will either get the Mossburg 500 or the Remington 870. Someone told me that one of these is better than the other in terms of where the trigger lock(or something) is in terms of ease of use for a right or left handed person.
The Safety. on the mossburg it will work equally righty or lefty
Also, regarding recoil in case my little wife needed to use it. Is the 12 that much more intense(felt recoil) than the 20 gauge.
Yes the 12 will have more recoil but unless you intend to shoot the bad guy 25 times or so it shouldn't be a problem. More than likely if push comes to shove when you work the action within ear shot of the bad guy he/she will go bye-bye pronto.
Also can you mount any of the available tactical lights on the 20 if I wanted to do that? Hang in their folks. One more. It seems that both the 500 and 870 come in a few variations within that model number. Anything that stands out as a preference?
Get one with sights like a rifle. and a 20" or less barrel.
Most of the "Law Enforcement" models will handle all sorts of attachments
I would make several comments regarding your questions. I would suggest either the 870 or 590. Those tend to be the choice for serious self-defense shotgunners. Personally, I prefer the 870. I hunt with an 870 so I like the consistency. I like the fit and finish better on the 870 (personal choice). I also like the wide availability of parts due to its popularity and years of production.
As the previous poster mentioned, the 870 has the safety at the rear of the trigger guard so it is not easily operated by both left and right handed shooters. The 590 has it mounted on the tang so it works well for either.
If you desire a butt stock with integrated pistol grip, the 870 is a better choice since operating the tang safety on the 590 is difficult without breaking your firing grip.
If you are going to mount a side saddle, the 870 has a steel receiver so it is more rugged (also heavy). Although I am not positive, I thought the 500/590 had an alumium receiver. Maybe someone can confirm. If so, you want to be careful mounting a traditional side-saddle on it since the screws can damage the receiver over time.
You will want to get a fore-stock with an integrated light. They are readily available for both the 590 and 870. Also consider a ghost ring sighting system with a tritium front sight. They are nice upgrades, especially for slugs at any distance. Having said that, there are plenty of skilled folks that use bead sights just fine.
As far as 12 vs. 20, unless you have a real reason to go for a 20, I would suggest the 12 gauge. Many would argue that the 20 is a limited shotgun for home defense. Hard to get 00 buck in a 20 gauge. You have much more flexibility with a 12 gauge. If you are worried about the occasional use your wife might have, get her a 20 of her own or let her train with light loads in the 12 gauge. And yes, the recoil difference is significant but so can be the stopping power.
Finally, lots of people like the semi-auto Benelli's for home defense. You may also want to consider one of those.
As the previous poster mentioned, the 870 has the safety at the rear of the trigger guard so it is not easily operated by both left and right handed shooters. The 590 has it mounted on the tang so it works well for either.
If you desire a butt stock with integrated pistol grip, the 870 is a better choice since operating the tang safety on the 590 is difficult without breaking your firing grip.
If you are going to mount a side saddle, the 870 has a steel receiver so it is more rugged (also heavy). Although I am not positive, I thought the 500/590 had an alumium receiver. Maybe someone can confirm. If so, you want to be careful mounting a traditional side-saddle on it since the screws can damage the receiver over time.
You will want to get a fore-stock with an integrated light. They are readily available for both the 590 and 870. Also consider a ghost ring sighting system with a tritium front sight. They are nice upgrades, especially for slugs at any distance. Having said that, there are plenty of skilled folks that use bead sights just fine.
As far as 12 vs. 20, unless you have a real reason to go for a 20, I would suggest the 12 gauge. Many would argue that the 20 is a limited shotgun for home defense. Hard to get 00 buck in a 20 gauge. You have much more flexibility with a 12 gauge. If you are worried about the occasional use your wife might have, get her a 20 of her own or let her train with light loads in the 12 gauge. And yes, the recoil difference is significant but so can be the stopping power.
Finally, lots of people like the semi-auto Benelli's for home defense. You may also want to consider one of those.
Limeyfellow
New member
I had the pleasure/punishment to fire a 10 gauge double barrelled from the late 1880s. That was enough to intimidate almost anyone facing the business end. I would go with the 12 gauge too for the ease of getting the shells at a cheaper price and the superior firepower. Plus you have the added bonus of putting in a slug and watching your wife fire and land on her backside. Good memories.
Skeetin'870
New member
The 590 does have an alumium reciever. But it does come with the stock 8+1 capacity. They are fine guns just ask rugerdude he uses his for skeet and outshoots the guy with the 6000 dollar krieghoff. who has been shooting five times longer then we have
Either will do. While I'm an 870 fan, the Mossbergs are good shotguns. Southpaws may find the Mossie with its dorsal safety easier to handle.
Since you mentioned your wife, one fine defensive shotgun is the Remington Youth Model 1100 in 20 gauge. Less kick and fun to shoot.
20 gauge will do the job, but ammo selection is more limited.
HTH....
Since you mentioned your wife, one fine defensive shotgun is the Remington Youth Model 1100 in 20 gauge. Less kick and fun to shoot.
20 gauge will do the job, but ammo selection is more limited.
HTH....
big daddy 9mm
New member
I own a mossberg 500
it is a great gun. I it not the best for SD just because the barrel is kinda long but I agree with statement about the 590. it is more geared for SD. also check out winchester 1300's they look really nice. I once was told by a friend that 20 gauge was alot kick for a little bit power, afetr shooting one I found out that that was complete bull shiit. I wish my shotgun was a 20 just becauseit takes the edge off the kick a little and you only lose a very small bit of power. and the bullets go just as fast as the 12.
it is a great gun. I it not the best for SD just because the barrel is kinda long but I agree with statement about the 590. it is more geared for SD. also check out winchester 1300's they look really nice. I once was told by a friend that 20 gauge was alot kick for a little bit power, afetr shooting one I found out that that was complete bull shiit. I wish my shotgun was a 20 just becauseit takes the edge off the kick a little and you only lose a very small bit of power. and the bullets go just as fast as the 12.
Here is a clip from the this web site: http://www.chuckhawks.com/ammo_by_anonymous.htm
I am not sure I agree with the comments fully, I thought it was interesting reading. I, for one, am sold on 00 buck. Here is the first portion of the text regarding shotguns:
SHOTGUN AMMUNITION BY CALIBER (Gauge)
The shotgun is the ne plus ultra of manstoppers. No other weapon will put a man down as reliably as a shotgun, and no other weapon is as likely to hit your opponent as a shotgun filled with buckshot. No doubt you have heard a lot of nonsense about the lethality of "assault rifles" and "Uzi sub-machine guns" and the like. The fact is that the shotgun is by far the deadliest and most effective firearm for short-range personal defense. For example: an Uzi or Heckler & Koch sub-machine gun has about 340 ft-lbs. of impact energy - a 12 gauge shotgun has 2500 to 3100 ft-lbs. of impact energy, and it is a heck of a lot easier to hit your target with a shotgun than a sub-machine gun.
The shotgun is not a magic weapon that will slay all foes, but it is simply the most effective man-stopping firearm yet devised. I invoke the Ascended Master, Massad Ayoob: "It is perhaps the most efficient close-range killing machine in the world's arsenal of small arms." For a discussion of the shotgun's strengths and weaknesses I refer all interested parties to Ayoob's excellent and comprehensive book 'The Truth About Self-Protection' (truly the best $8.95 investment you'll ever make), which discusses every element of self-defense from locks, chemical sprays and alarms to defensive driving, firearms and defending yourself against dogs. A more in-depth treatment of the issue may be found in Ayoob's book-length volume on shotgun technique, 'Stressfire II: Advanced Combat Shotgun'.
A Note On Terminology
Shotgun ammunition falls into three general categories:
BUCKSHOT - shell loaded with large-diameter lead balls (.24" and up) used for big game hunting and self-defense. The number of pellets in 12 gauge buck-shot varies from eight .36" balls in "000 buck" to 27 .24" pellets in "#4 buck". Buckshot ratings are archaic and hard to understand (as are shotgun specifications and ammunition in general), but thankfully there isn't much you need to learn. Simply write down the recommended loads, walk into your local gunshop and announce your desired ammunition (note that "00" is pronounced "double ought" and "000" is pronounced "triple ought." Don't say "zero zero" or "oh-oh-oh buckshot" in front of gunshop employees - they will snicker and mock you cruelly behind your back). Then practice with both your selected defense load and low-cost birdshot to fully familiarize yourself with the operation of your gun and its terminal performance (e.g. patterns at various distances, the startling effects of buckshot on ballistic melons).
BIRDSHOT- small-diameter pellets used for bird hunting. Its stopping power is poor, except when used at very close range - out to 20-30 feet. For that reason it is not generally recommended, except for home defense use.
SLUGS are solid lead bullets for shotgun use. These are big, heavy, fat hunks of soft lead that have enormous stopping power (e.g. a typical 12 gauge slug is .73" caliber and weighs 438 grains - a 9mm bullet is .355" and 115 grains). Use of slugs ruins the shotgun's main advantage - superior hit probability - as slugs must be carefully aimed to be effective. It is important to remember, however, that shotguns must be aimed with shot, too - do not for a minute think that you can simply point your shot-loaded shotgun at the foe and let loose. Shotguns must be skillfully aimed and fired just like hand-guns and rifles. The shotgun is simply more likely to hit the attacker.
.410 Gauge
None of the above really applies in this weak caliber. The .410 is only a half-way decent manstopper with slugs. Choose the Federal Classic (F412RS) or Winchester Super-X (X41RS5) 1/5 ounce (88 grain) hollowpoint slug. Never use birdshot. American Derringer Corp. has produced an odd buckshot load for the .410 (withthree 000 pellets), and I advise you to ignore it. Lose the .410 and buy a 20 gauge pump shotgun.
20 Gauge
The 20 is an excellent self-defense caliber, particularly for those who dislike the recoil of the 12 gauge. I recommend the 20 gauge over the more popular 12 for home defense. Choose the 20 gauge 3" shell Federal "Classic" #2 buckshot (F207-2-5PK) with 18 pellets, or the Winchester "Double XX" Magnum #3 with 24 pellets (X203C3B). If your gun cannot accept 3" shells choose the Remington #3 with 20 pellets (SP20BK5PK-3). All of these loads provide definitive short-range stopping power.
I specifically recommend the 20 gauge for women and recoil-sensitive men who dislike the blast and recoil of the 12 gauge. "Delivering roughly the ballistic force of two .44 Magnum rounds at once," comments the knowledgeable Ayoob, the 20 "delivers 75% of the lead for only 50-60% of the recoil". Many police departments have found their officers shoot much more accurately in realistic training exercises with the lighter-kicking but still potent 20 gauge.
If you are new to shotgunning and considering getting one for self-defense I strongly urge you to buy the reliable and reasonably-priced "Mossberg 500 Special Purpose" 18.5" barrel 20 gauge pump shotgun (catalog #50451). This tried-and-true workhorse is the standard shotgun of the U.S. Armed Forces and costs a little over $200. You'll be much happier with the lighter-kicking 20 gauge than the 12 gauge version used by the military, and - most importantly - you'll shoot the 20 more accurately and rapidly.
For an in-depth look at the 20-versus-12 gauge issue I recommend all shotgun owners (and potential shotgun owners) read 'Stressfire II: Advanced Combat Shotgun' by Massad Ayoob. Perhaps I am beginning to sound like a broken record on the theme of Ayoob's books, but once you've read them you'll understand why I recommend them so highly (and repeatedly). Note: Ayoob dislikes the 20 gauge Remington 870 pump shotgun and recommends you choose the Mossberg 500 in 20 gauge for general self-defense and home-defense use. So do I.
For ultra-close range home defense birdshot will do the trick. Choose any #4, BB or larger high brass lead hunting load, and have the balance of the magazine filled with #3 buck in case the birdshot doesn't put them down fast enough.
Avoid slug use in 20 gauge; you are better off defending yourself with buckshot. If you must use slugs, pick the Dynamit/Nobel or Federal "Classic" (F203-RS) rifled slugs. Using slugs requires careful aiming and rifle sights: few 20 gauge shotguns have the latter.
16 Gauge
The 16 has slipped in popularity with Americans. As a result, no shotguns made specifically for defense are available in 16. If you have a sporting 16, however, it can do double duty as a great defense gun. Choose the Federal "Classic" #1 (F164-1) or the Remington #1 (SP16BK-5PK) buckshot load.
I am not sure I agree with the comments fully, I thought it was interesting reading. I, for one, am sold on 00 buck. Here is the first portion of the text regarding shotguns:
SHOTGUN AMMUNITION BY CALIBER (Gauge)
The shotgun is the ne plus ultra of manstoppers. No other weapon will put a man down as reliably as a shotgun, and no other weapon is as likely to hit your opponent as a shotgun filled with buckshot. No doubt you have heard a lot of nonsense about the lethality of "assault rifles" and "Uzi sub-machine guns" and the like. The fact is that the shotgun is by far the deadliest and most effective firearm for short-range personal defense. For example: an Uzi or Heckler & Koch sub-machine gun has about 340 ft-lbs. of impact energy - a 12 gauge shotgun has 2500 to 3100 ft-lbs. of impact energy, and it is a heck of a lot easier to hit your target with a shotgun than a sub-machine gun.
The shotgun is not a magic weapon that will slay all foes, but it is simply the most effective man-stopping firearm yet devised. I invoke the Ascended Master, Massad Ayoob: "It is perhaps the most efficient close-range killing machine in the world's arsenal of small arms." For a discussion of the shotgun's strengths and weaknesses I refer all interested parties to Ayoob's excellent and comprehensive book 'The Truth About Self-Protection' (truly the best $8.95 investment you'll ever make), which discusses every element of self-defense from locks, chemical sprays and alarms to defensive driving, firearms and defending yourself against dogs. A more in-depth treatment of the issue may be found in Ayoob's book-length volume on shotgun technique, 'Stressfire II: Advanced Combat Shotgun'.
A Note On Terminology
Shotgun ammunition falls into three general categories:
BUCKSHOT - shell loaded with large-diameter lead balls (.24" and up) used for big game hunting and self-defense. The number of pellets in 12 gauge buck-shot varies from eight .36" balls in "000 buck" to 27 .24" pellets in "#4 buck". Buckshot ratings are archaic and hard to understand (as are shotgun specifications and ammunition in general), but thankfully there isn't much you need to learn. Simply write down the recommended loads, walk into your local gunshop and announce your desired ammunition (note that "00" is pronounced "double ought" and "000" is pronounced "triple ought." Don't say "zero zero" or "oh-oh-oh buckshot" in front of gunshop employees - they will snicker and mock you cruelly behind your back). Then practice with both your selected defense load and low-cost birdshot to fully familiarize yourself with the operation of your gun and its terminal performance (e.g. patterns at various distances, the startling effects of buckshot on ballistic melons).
BIRDSHOT- small-diameter pellets used for bird hunting. Its stopping power is poor, except when used at very close range - out to 20-30 feet. For that reason it is not generally recommended, except for home defense use.
SLUGS are solid lead bullets for shotgun use. These are big, heavy, fat hunks of soft lead that have enormous stopping power (e.g. a typical 12 gauge slug is .73" caliber and weighs 438 grains - a 9mm bullet is .355" and 115 grains). Use of slugs ruins the shotgun's main advantage - superior hit probability - as slugs must be carefully aimed to be effective. It is important to remember, however, that shotguns must be aimed with shot, too - do not for a minute think that you can simply point your shot-loaded shotgun at the foe and let loose. Shotguns must be skillfully aimed and fired just like hand-guns and rifles. The shotgun is simply more likely to hit the attacker.
.410 Gauge
None of the above really applies in this weak caliber. The .410 is only a half-way decent manstopper with slugs. Choose the Federal Classic (F412RS) or Winchester Super-X (X41RS5) 1/5 ounce (88 grain) hollowpoint slug. Never use birdshot. American Derringer Corp. has produced an odd buckshot load for the .410 (withthree 000 pellets), and I advise you to ignore it. Lose the .410 and buy a 20 gauge pump shotgun.
20 Gauge
The 20 is an excellent self-defense caliber, particularly for those who dislike the recoil of the 12 gauge. I recommend the 20 gauge over the more popular 12 for home defense. Choose the 20 gauge 3" shell Federal "Classic" #2 buckshot (F207-2-5PK) with 18 pellets, or the Winchester "Double XX" Magnum #3 with 24 pellets (X203C3B). If your gun cannot accept 3" shells choose the Remington #3 with 20 pellets (SP20BK5PK-3). All of these loads provide definitive short-range stopping power.
I specifically recommend the 20 gauge for women and recoil-sensitive men who dislike the blast and recoil of the 12 gauge. "Delivering roughly the ballistic force of two .44 Magnum rounds at once," comments the knowledgeable Ayoob, the 20 "delivers 75% of the lead for only 50-60% of the recoil". Many police departments have found their officers shoot much more accurately in realistic training exercises with the lighter-kicking but still potent 20 gauge.
If you are new to shotgunning and considering getting one for self-defense I strongly urge you to buy the reliable and reasonably-priced "Mossberg 500 Special Purpose" 18.5" barrel 20 gauge pump shotgun (catalog #50451). This tried-and-true workhorse is the standard shotgun of the U.S. Armed Forces and costs a little over $200. You'll be much happier with the lighter-kicking 20 gauge than the 12 gauge version used by the military, and - most importantly - you'll shoot the 20 more accurately and rapidly.
For an in-depth look at the 20-versus-12 gauge issue I recommend all shotgun owners (and potential shotgun owners) read 'Stressfire II: Advanced Combat Shotgun' by Massad Ayoob. Perhaps I am beginning to sound like a broken record on the theme of Ayoob's books, but once you've read them you'll understand why I recommend them so highly (and repeatedly). Note: Ayoob dislikes the 20 gauge Remington 870 pump shotgun and recommends you choose the Mossberg 500 in 20 gauge for general self-defense and home-defense use. So do I.
For ultra-close range home defense birdshot will do the trick. Choose any #4, BB or larger high brass lead hunting load, and have the balance of the magazine filled with #3 buck in case the birdshot doesn't put them down fast enough.
Avoid slug use in 20 gauge; you are better off defending yourself with buckshot. If you must use slugs, pick the Dynamit/Nobel or Federal "Classic" (F203-RS) rifled slugs. Using slugs requires careful aiming and rifle sights: few 20 gauge shotguns have the latter.
16 Gauge
The 16 has slipped in popularity with Americans. As a result, no shotguns made specifically for defense are available in 16. If you have a sporting 16, however, it can do double duty as a great defense gun. Choose the Federal "Classic" #1 (F164-1) or the Remington #1 (SP16BK-5PK) buckshot load.
Here is the second portion:
12 Gauge
If you have a 12 gauge shotgun you own the most effective and devastating short-range firearm ever created. If you simply want to know the best defense load, go out and buy: 12 gauge 2 3/4" shell 00 buckshot. You shall live happily ever after, as this is the most effective man-stopping firearm cartridge yet devised by man. I recommend the Federal "Classic" (F127-00), Winchester Super-X (X12RB5) or Remington Buckshot (SP12BK-5PK00) as the best double-ought buckshot defense rounds. One of these rounds is virtually equal to a nine-round burst from a submachine gun, with every round hitting.
Effective shotgun technique, of course, requires that one hits with each shot. Don't think that you can merely point the shotgun in the general direction of your attacker and let fly. Read Ayoob's book 'Stressfire II: Advanced Combat Shotgun' for the low-down on good shotgun skills and then practice, practice, practice.
Many experienced shooters prefer #4 or #1 buckshot to 00. I really cannot argue, but Lt. Marshall is on record as stating that 00 is superior, both in penetration and stopping power. Good enough for me, but if you have a #4 or #1 buckshot jones, go ahead (Ayoob favors #1). Stay away from 2 3/4" Magnum or 3" Magnum loads, however - the brutal kick of these rounds makes them a bad choice, and you gain nothing in stopping power over the 2 3/4" standard loads. Controllability is important, and standard 12 gauge shells have quite enough kick as it is.
A note on shotgun spread: firing your shotgun does not create a diabolical cone of doom destroying all in its path. If you have a typical defense or "riot" gun with an 18"-20" open-choked "cylinder" barrel, the pellets will spread out about 1" for every yard of range. This means that the spread of pellets fired across a large room (18') will be 6" or so, a circle the size of a coffee cup saucer. At 50 feet, the spread will be the size of a large pizza (16"). Test-fire your shotgun at various ranges, using big white butcher paper targets to get an idea of the pattern you can expect. It is a common misconception that blasting at foes ten feet away will take out two or three of them. The spread at that range is just three inches, so you can see that I meant it when I said that the shotgun must be skillfully aimed and fired just like handguns and rifles. The shotgun is simply more likely to hit - and stop - the attacker.
Slugs are potent manstoppers, but have limited application for self-defense. Slug use loses the one big advantage of the shotgun - its high hit probability. Slugs have ferocious recoil and often over-penetrate. There are special situations where slugs might be preferred over buckshot (e.g. road-blocks, barricaded foes), but if you are interested in such esoterica I again direct you to Ayoob's masterful tome 'Stressfire II: Advanced Combat Shotgun'. This guide is for general civilian readers; policemen, soldiers, and gun enthusiasts should rely on Ayoob's in-depth expertise.
Don't be a knucklehead. Stay away from weirdo rounds like rubber buckshot or neoprene slugs. These are riot-control rounds designed for massed police use against violent mobs. Don't rely on such marginalia to save your life.
Two things to keep in mind about birdshot. The first is that birdshot is as lethal as buckshot at close range. Don't believe for a second that you can just wound someone with birdshot and he'll go on to live another day. If you aren't justified in killing a man, you aren't justified in wounding him, either. Never "shoot to wound." I once again direct you to read Ayoob's 'In the Gravest Extreme' and learn the truth.
The second thing is that birdshot makes a lot of sense for home defense. I keep my home-defense 12 gauge loaded with two #4 birdshot rounds followed by 00 buck. Birdshot is much less likely to penetrate thin interior walls and kill innocent people on the other side, and has lower recoil than buckshot for faster follow-up shots (I live in a thin-walled apartment house, however - if I lived in a solid house with a lot of land around, I would definitely choose buckshot instead). The stopping power of birdshot should not be under-estimated: at ranges out to thirty feet or so, birdshot is virtually a solid column of lead (imagine an angry swarm of bees chasing Elmer Fudd and you'll get the idea). Choose any #4 or BB high brass lead hunting load. I like the Federal "Classic Lead Hi-Brass" #4 birdshot (HI26-4) and Winchester "Super-X" #4 high brass birdshot (X12-4), but there is little difference between the various choices. Buy whichever you please. If you're a bird hunter, use your favorite hunting shells as long as they are #6 or larger.
10 Gauge
Yow. Load your 10 gauge with whatever the hell you want.
12 Gauge
If you have a 12 gauge shotgun you own the most effective and devastating short-range firearm ever created. If you simply want to know the best defense load, go out and buy: 12 gauge 2 3/4" shell 00 buckshot. You shall live happily ever after, as this is the most effective man-stopping firearm cartridge yet devised by man. I recommend the Federal "Classic" (F127-00), Winchester Super-X (X12RB5) or Remington Buckshot (SP12BK-5PK00) as the best double-ought buckshot defense rounds. One of these rounds is virtually equal to a nine-round burst from a submachine gun, with every round hitting.
Effective shotgun technique, of course, requires that one hits with each shot. Don't think that you can merely point the shotgun in the general direction of your attacker and let fly. Read Ayoob's book 'Stressfire II: Advanced Combat Shotgun' for the low-down on good shotgun skills and then practice, practice, practice.
Many experienced shooters prefer #4 or #1 buckshot to 00. I really cannot argue, but Lt. Marshall is on record as stating that 00 is superior, both in penetration and stopping power. Good enough for me, but if you have a #4 or #1 buckshot jones, go ahead (Ayoob favors #1). Stay away from 2 3/4" Magnum or 3" Magnum loads, however - the brutal kick of these rounds makes them a bad choice, and you gain nothing in stopping power over the 2 3/4" standard loads. Controllability is important, and standard 12 gauge shells have quite enough kick as it is.
A note on shotgun spread: firing your shotgun does not create a diabolical cone of doom destroying all in its path. If you have a typical defense or "riot" gun with an 18"-20" open-choked "cylinder" barrel, the pellets will spread out about 1" for every yard of range. This means that the spread of pellets fired across a large room (18') will be 6" or so, a circle the size of a coffee cup saucer. At 50 feet, the spread will be the size of a large pizza (16"). Test-fire your shotgun at various ranges, using big white butcher paper targets to get an idea of the pattern you can expect. It is a common misconception that blasting at foes ten feet away will take out two or three of them. The spread at that range is just three inches, so you can see that I meant it when I said that the shotgun must be skillfully aimed and fired just like handguns and rifles. The shotgun is simply more likely to hit - and stop - the attacker.
Slugs are potent manstoppers, but have limited application for self-defense. Slug use loses the one big advantage of the shotgun - its high hit probability. Slugs have ferocious recoil and often over-penetrate. There are special situations where slugs might be preferred over buckshot (e.g. road-blocks, barricaded foes), but if you are interested in such esoterica I again direct you to Ayoob's masterful tome 'Stressfire II: Advanced Combat Shotgun'. This guide is for general civilian readers; policemen, soldiers, and gun enthusiasts should rely on Ayoob's in-depth expertise.
Don't be a knucklehead. Stay away from weirdo rounds like rubber buckshot or neoprene slugs. These are riot-control rounds designed for massed police use against violent mobs. Don't rely on such marginalia to save your life.
Two things to keep in mind about birdshot. The first is that birdshot is as lethal as buckshot at close range. Don't believe for a second that you can just wound someone with birdshot and he'll go on to live another day. If you aren't justified in killing a man, you aren't justified in wounding him, either. Never "shoot to wound." I once again direct you to read Ayoob's 'In the Gravest Extreme' and learn the truth.
The second thing is that birdshot makes a lot of sense for home defense. I keep my home-defense 12 gauge loaded with two #4 birdshot rounds followed by 00 buck. Birdshot is much less likely to penetrate thin interior walls and kill innocent people on the other side, and has lower recoil than buckshot for faster follow-up shots (I live in a thin-walled apartment house, however - if I lived in a solid house with a lot of land around, I would definitely choose buckshot instead). The stopping power of birdshot should not be under-estimated: at ranges out to thirty feet or so, birdshot is virtually a solid column of lead (imagine an angry swarm of bees chasing Elmer Fudd and you'll get the idea). Choose any #4 or BB high brass lead hunting load. I like the Federal "Classic Lead Hi-Brass" #4 birdshot (HI26-4) and Winchester "Super-X" #4 high brass birdshot (X12-4), but there is little difference between the various choices. Buy whichever you please. If you're a bird hunter, use your favorite hunting shells as long as they are #6 or larger.
10 Gauge
Yow. Load your 10 gauge with whatever the hell you want.