If you really want penetration then use 0000 (.380 dia) buckshot instead of 00 (.330 dia) buckshot but if you want to hit your target, give it severe trauma, then you have to lessen the diameter like to maybe #2 (.270 dia) or #4 (.240 dia) buckshot (my #1 favourite load)...why, you ask, because there is 3 to 4 times the number of pellets, allowing three to four times more possibilities of, hitting your target. There is in a one (1) ounce (oz.) load = 6.25 in 000, 8.13 in 00, 12.5 in #2 and 20.3 in #4 of pellets...I think there are 3½ or more likely 4 in 0000 (quad Aught) buck.
There are other pellet sizes available, but you'll probably have trouble finding them, locally; like #1 (.300/10.16 per oz), #F (.220/39 per oz) & my 2nd most favourite load, #TT (.210/46 per oz) and that would be the smallest I would go for home defence. The #F loading is like emptying 3 twenty five round banana or 7 regular rotary clips of .22 ammo
all at onceat the target. Which do you think would hit, 9 00 buckshot or 70 #F buckshot, especially at 10, 15 or 20 yards, were most home defence is conducted.
The closer in you are the more spread you need whilst farther out you require a tighter pattern. Most tactical shotguns are bored cylinder (C or cyl) or improved cylinder (IC or Imp Cyl). I prefer a slightly tighter choke, a modified (M or Mod) or an improved modified (IM or Imp Mod) allowing me to have a deeper shooting zone. What really gets me irked is seeing on TV or in the movies, people shooting at a person 100 yards away with a shotgun. At 40 yards you'll get about a 12' spread in your pellets (the width of a room) or about ¾ of a pellet of 00 buckshot per foot with an Imp Cyl choke. At 100 yards that expands to approximately a 30' to 35' (width of a house) spread or about 1 pellet in 3&¾' of space. If they're hit out there, then they have to be the unluckiest people going. Mind you, any size pellet would only irritate you, at best, at that distance. The chance of getting hit with a quad aught pellet might wound you if it hit in a fleshy area. No mass, no velocity, no energy = no wound.
You can mix your own concoctions up by adding #BB (.180 dia/50 per oz) or #2 (.150 dia/124 per oz) birdshot to your #2 or #4 and #F buckshot rounds as filler. Makes for a lovely halo around the massive hole close in...anything smaller just adds an irritant factor to the equation.
I would load my pump with 3 buck rounds, followed by 2 slug rounds and then followed by 1 buck round. This is on an empty chamber but with my last buckshot round out so that I can insert it after racking the slide. This would give me a 3/2/2 configuration. I have a Rossi exposed hammer 12 bore 18½” double barrel coach gun on my side of the bed and a matching 20 bore on my wife’s side. All are equipped with a combination slip on recoil pad (Limbsaver), padded cheek pad and a 8 slot leather loop ammo carrier that I had a saddle maker stitch up for me. All but one are lace up as I had wanted to try one with a Velcro closure…very quick to adjust but very loud. I have a Surefire tactical flashlight mounted below barrels, a leather cobra style sling with 12 extra leather ammo loops on the wide part and a barrel shroud to protect your hands from the heat of the barrels and to hold the flashlight. I’m having another set made up with some very minor design changes to correct some errors I made and will all be fancied up with basket weave carving.
Although I truly dislike slugs for home defence, as there is only one projectile going out to the target...sort of defeats the purpose of the shotgun...I load them towards the end--in case I need the extra range they provide. Don't get me wrong here, I think slugs are fantastic, for hunting, but if I'm defending my home I want spread, coverage and penetration. You blast someone with a load of #9 Skeet (.080 dia/897 per oz) at 5 feet away your going to have a dead body with one big hole in them...the same as what a one ounce slug would do...you go out to 30 yards and if they would be wearing a heavy leather coat, the pellets would probably just bounce off or maybe just penetrate the leather. To penetrate you have to either increase the velocity or the mass or both.
To see the effect of using too light a load of pellets and/or too far away--view here
Bird Shot Human Torso
picture link: http://www.bootsandsabers.com/index.php/photo_gallery/image_med/61/