Using a Mossberg 500 for home defense. used the original 24" barrel to practice and pattern my ammo but finally bought an 18" defensive barrel. Here’s the question, My plan involves holing up in the master bedroom barricading the door, calling 911 and using the shotgun to defend the door. so I patterned my rounds at 3 to 5 yards. when I began to practice with the 18" barrel I found that the groupings of low recoil, 12ga, 2 3/4 inch, 9 pellet, 00 buckshot actually patterned a smaller group then when fired from my 24" barrel. how did that happen? I have an idea why that might have happened but initially I thought, longer barrel, smaller group. how come my groups are smaller with the shorter barrel?
thanx
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Longer barrel with the same powder charge will equate to higher velocity, and possibly more deformation of the pellets under that acceleration?
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What’s the choke on the long barrel?Full choke will give a much tighter pattern where as modified opens it up. 18 inch mossy defense barrels are cyl choke or basically there is none.
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That was my next guess, different chokes between the two barrels
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Not giving a silly response but at that range that grouping should be good. No stray pellets all where you want them. Have you thought about shooting slugs?
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Concern with slugs at that range is pass through.
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I have the same gameplan, William987. Maybe a little more extreme in my planning, but essentially the same.
I have two questions for you.
Are there chokes in these two barrels or are both cylinder bore? What is the spread of each barrel?
Typically, the longer the barrel the tighter the pattern due to the longer time the shot has to stabilize and remain in a tighter column as it travels through the barrel. A couple “external” things that will influence your pattern are the model of the choke, if installed, and the brand of ammo used in your testing,
A tight choke, like a full choke, will give a tighter pattern than a cylinder boar with no choke.
The brand of ammo (the quality) can be a key player in this also. Remembering back to when I had my first HD shotty and was doing my patterning, I managed to get my hands on some absolutely dirt cheap (cheap quality) ammo because I knew I was going to waste it all testing. It has been so long ago I don’t even remember the brand. Let me just say it was inconsistent. Some rounds felt like I was getting kicked by a mule and other rounds felt like I was plinking with a .22LR.
Whatever round you will use to defend your family is the one you need to pattern with.
The 3 - 5 yards you are patterning at is ok for inside the master bedroom. Do yourself a favor and measure the longest distance you might need to shoot inside your home and pattern at that distance also. Getting a fist sized pattern at 3-5 yards will open up exponentially at 10-12 yards, and who is to say you will only be using your shotty just in the MBR?
Use your hand gun to fight to your long gun. Use your long gun to clear all your loved ones into the MBR. Use your Mossy 500 as artillery until the cavalry arrives.
This is a major concern. 
EVERYTHING will over penetrate the walls of your home. Stay focused on what is behind your target.
The 12-gauge shotgun is a highly devastating weapon in the hands of a trained warrior. That would be you, defending your home. It is so devastating that Hitler tried to have them outlawed for use in WW2 because it gave us an 'UNFAIR" advantage. We know who won WW2. It wasn’t Hitler.
Two additional points and I will get off my soap box.
The racking of the slide on a pump action shotgun or cycling the charging handle on an autoloader will tell your opponent EXACTLY where you are.
The racking of the slide on a pump action shotgun or cycling the charging handle on an autoloader will also tell your opponent you just opened a can of whoop-ass.
Peace.
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@William987 Good to see you and a great question. I use a Remington 870 with the bird barrel. I will say I do use a modified choke.
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Buckshot through a full choke barrel can display odd behavior. Nine 32 caliber projectiles travelling through a restricted bore in short order plays havoc on an orderly exit as they collide.
Your MBR Alamo plan is sound and at room distances you should expect a 2 inch pattern on whatever happens to have the misfortune of placing itself in its way. Always have in mind what is behind “it”, but an aimed shot, center mass at that distance with 00 buck should not present a pass through issue and would be a devastating man stopper.
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I wouldn’t use a shotgun, and I cannot barricade, I have other family members in the house, therefore, my plan is much different than yours, too many variables to have a plan that fits everyone, I am going mobile, I know the terrain, and hunting humans breaking into my house would be very cool indeed.
Layered defense is best, fences, dogs, alarms, cameras all scream to the bad guys to move to the next house. But, if they still make that fatal mistake, I will be the one calling 911, after I clean their pockets of cash for the damages.
I don’t fight fair, I have yet to find a rule book on warfare that I accept, so that’s why I wear (after the alarm sounds):
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Barrel to barrel differences. Choke. Sometimes it varies, good on you for testing.
As for the plan…it’s great. Just remember that everyone has a plan until they get punched in the mouth. Or something like that.
Who is to say that you will be in the master bedroom if someone breaks in, and you will not have any reason to leave that room? Be prepared to be versatile, pattern farther than 5 yards.
Try to get your hands on some Federal flite control or Hornady Critical Defense with the versatile whatever technology (same thing) for use with cylinder chokes especially
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I’m not a Tier One operator. Never was. It’s fun to play one in a computer game though.
You are correct in a couple points you made. Having a layered defense is always best. The more layers, the better. More warning before the intruders get to you.
My plan doesn’t work for you and your plan doesn’t work for me. There are different dynamics involved from the jump and in a home defense situation, only you can see what you see. No one else is there, so even though you have a gameplan, things will occur that you didn’t plan for and you will need to make it up as you go.
Well, back to the old drawing board…
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Barricaded, behind mattress, round in chamber, muzzle aimed at doorway and call made with speaker on. 
Wandering ninja like around the dark house thinking you’ll sneak up on a bad guy? 
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Funny, I never owned a computer game. And I would never consider myself a Tier One, but I was on and instructed a Special Operations Team in the Military, Having the bells and whistles does not mean highly professionalized, being in shape does not, understanding and knowing the tactics does not, having the heart to work the problem does not, having all the other resources does not, I am retired, I no longer have a multi-million dollar bank rolling Uncle Sam, in fact I no longer have access to helio’s and other aircraft, no more flex linear or flash-bangs or unlimited ammo of all sorts, hell, in fact, I can’t even shoot a Goat and fix it up again, no more repelling, or fast roping, no more crisis entries, of sniper/counter sniper, no more getting really ass drunk at the local hole with my team, my gym has shrunk, my knees are shot, my shoulder was replaced, I have a new right knee and they took my appendix out in Arizona, my molars out in South Korea, stitched my hand up in New Mexico, and they gave me 100% disability one day and said adios.
So, I wear my own NVG’s on my helmet, have IR light sticks, and my AR is GOATED out for those who wish to enter my house uninvited, (Or my suppressed 9mm) therefore, I would jump at the chance to go mobile in my castle, yes sir, back in the saddle.
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You made some pretty good points until you got on your soapbox.
Is the handgun on your nightstand or wherever you keep it at night. Is it loaded or unloaded?
Do you carry with one chambered or not?
Why would your home defense shotgun be unloaded? Why wouldn’t they’re already be one in the chamber?.
and a perfect world. The bad guy should never hear you, rack it .
Jmo.
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I have to rack one into my suppressed 9mm, as my PTSD nightmares screw with me, I was shooting at Black Hawks one night, the pilot and door gunners were green bunny rabbits. I woke up in a sweat, my wife was laughing while I issued commands for my team to use their shoulder fire weapons to take the bunny fighters out, so…
I have to ensure that there is a two step process in place to make my 9mm hot and ready to kill any bunnies that enter my castle. That’s just one dream, my weapon malfunctions when I pull the trigger and flubber material comes out. Just saying, I just do not have time to drink a cup of java first, but I do have to rack one in, 
I see your valid point.
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It also tells the bad guy where you are and that you have a gun.
We all have our reasons.to do things a particular way.
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I have a mossberg 500 home defense loaded slug, (2) 00, slug, (2)00, along with a 45acp locked and cocked. But it is just me and my wife so don’t have to worry about others in the house.
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