Hey everyone!! I've been doing some research on the ammo for the AR-15. Different calibers and such. Just wanted to get your opinions on what you prefer for home defense primarily. My setup will be a short 8"-12" barrel suppressed. Here are some of my observations so far:

5.56mm rounds are the safest for home defense if you are worried about over penetration since the rounds are so light, has a little pop to it suppressed, louder than 300BLK, but not as bad as 6.8mm

300BLK supersonics suppressed are the quietest out of short barrels of all these calibers, love how compact and quiet it is. This is my current hog hunting setup.  

6.8mm is the loudest and most powerful caliber for home defense at short distances, but I hear they destroy suppressors out of short barrels

6.5mm is the best for long range shooting, and almost as deadly as the 6.8mm, but not quite. So I'm leaning away from this caliber at the moment.  

So for my purposes of home defense the 6.8mm seems like a great choice, however noise and over penetration are both important factors as well. Part of me really likes the quietness of the 300BLK. And part of me really likes not having to worry as much about over penetration. So I'm kind of torn between the three calibers. Right now I do have a 10.5" 5.56mm suppressed setup, and I have a 8" 300BLK suppressed setup and I love them both. But I'm thinking about adding a 6.8mm SBR suppressed setup to the mix maybe in a 12" barrel. What caliber setup would you use for home defense and why? 

12 gauge, hands down

12 ga 3" heavy goose shot. It will turn their insides to mush but less likely than buckshot to over penetrate. You will mop the floor instead over repairing the wall

Haha I'll agree 12 gauge is great, but too loud and too long for me. I prefer the suppressed short barreled rifle personally. So let's stay on AR-15 rifle calibers for now.

Suppressed 5.56mm (MK318) out of a 10.5" barrel.

12-gauge or .308.

I keep electronic ear pro ready to go too.

Of the calibers you mentioned, I only roll 6.8 so that's my default choice. However, I don't go SBR or suppressed but wouldn't hesitate to use it to defend the home, or outside the home or shtf or for hunting deer, coyotes, pigs, elk, moose, bear....or whatever.

I don't normally have it out and ready for home defense use, I leave that to the night sighted Glock 17 on the night stand.

my HD set up is a G17 and a PSA 9mmAR with 8.5" barrel. both reliably send 147 HST's so I keep a qd belt with kydex G17 holster and 3 x 21 rd magpul GL9 mags full of them.
both guns respectably have a factory 17 and 18 mag plugged in already. Wife knows to grab the 12g and run to which ever door I DONT run to.

300 with either 110g Barnes tac-tx or Lehigh 115g CC would be my choice.

You can't usually go less than 11.5" in 5.56 with a suppressor, so I guess you can rule that out if your requirements are a shorter barrel and a suppressor. I have an 11.5 suppressed and I actually took the suppressor off because it makes the gun too long and front heavy for rapid indoors work. So my current setup is 11.5" AR with a PWS CQB on the end (I've not seen any flash yet with it, but I've actually only shot PMC .223, still I believe it is an excellent flash hider).

So I think the 300 blackout in an 8.5" is what you seek. If I had more money I'd probably go that route with a suppressor.

I really like the 300 BLK with supersonic bullets like the Hornady SST or VMAX or any other fast expanding or varmint type bullet.  The 300 BLK isn't as loud or have as much blast to me as a 5.56/.223 even without a suppressor. Distances are going to be short.  I REALLY like the 300 BLK and think it should be even more popular. It would be my choice for home defense, SHTF or riot. I find it easy to reload too.

Pretty sure that has been disproven time and again, NOT that it really matters. You have to consider bullet construction and potential backstop with ALL cartridges, buckshot and birdshot included. Certainly from my own informal testing "shooting shit up," I'm always amazed at what materials a bullet can sail right through-- even 22LR.

-Stooxie

Yeah I think I'm currently leaning towards using the 300BLK for home defense since it's purpose built for such short barrels suppressed. I think 6.8mm would do best for hunting. And 6.5mm for long range target shooting. And 5.56mm for SHTF.

Close... suppressed 5.56mm MK262 out of a 10.3" barrel

Why can't you go shorter than 11.5" with a can?  

I think he is talking about barrel length restrictions for the can.  Its also typically 10.5" 556 for most cans 

I use an LMT 10.5" barrel with a can just fine.  Works great without ever a hiccup.  Shoot Black Hills 5.56 50gr TSX for barrier blind, and Mk 262 for non-barrier blind.

I like the 556 best for HD because it the least likely to exit my home, the barrier blind loads perform so well terminally, and they seem to expand on contact with drywall which lessens penetration though multiple walls.

https://www.theboxotruth.com/the-box-o-truth-1-the-original-box-o-truth/

People who think drywall is going to stop anything need to spend some time either in the site above or doing their own testing. 

Rigid or crystalline materials are generally terrible at stopping bullets. More pliable and multi layered materials  (like phone books or kevlar) are better because they slow the bullet down over time.

Of course rigid materials work if thick enough or tough enough  (A500) but drywall ain't either. 

-Stooxie

MK262 or clone, currently 77gr IMI Razorcore, out of a 10.5" SBR with Specwar can.

6.8 VMAX

.

5.56 because that is what I have. Well, I also have 7.62 X 39, but it wasn't on the poll.
Just like 5.56 it is specific to ammo for best results.

Absolutely the same, 10.5" LMT, Mk 262, SpecWar 556 suppressor.
Was going to Hornady T2 556 75gr, but I've got lots more 262.

My choice as well for the same reasons. Currently have 2 mags loaded with Fusion MSR 62 grain.

Primary home defense? A handgun. You won't have time to open your safe and pull out an AR.

And what kind of giant uranium can do you have to have to make an 11.5" barrel too long and heavy?

If you had time to get the rifle, I'd go unsuppressed and with active ears. Blowback smoke kills my eyes indoors with no moving air.

With suppressor: 300bo.

Without, 5.56

Dont need to open a safe to get my rifle

I've seen these stated a lot over the years, but nobody has ever been able to support them with testing or real world data because they turned out to be marketing, not reality.

90gr TNT from 6.5 Grendel is a brutal HD load, and Federal sells it by the 50rd box.

In my 17.6" barrel, one string of 5 averaged 2900.4fps, the other 2880.8fps.

Other HD bullets are the 85gr Sierra HP Varminter, 95gr V-MAX, and 95gr Controlled Chaos.

With an SBR, you get superior terminal performance, an ideal hunting package, and long range capability that you wouldn't think possible from an SBR AR15.

You have more energy at the muzzle from a 10.5" Grendel than a 20" 5.56.

6.5 Grendel suppresses well.  Ti cans like the TBAC Ultra are rated down to 11.5" barrels with 6.5 Grendel, same as 5.56.  The TBAC Ultra 5 is extremelly quiet with 6.5 Grendel in my experience, and doesn't even feel like a can on the muzzle, it so light.

This is the first I've heard that 6.8s trash cans, as they generally punt short bullets with fast powders, leading to lower muzzle pressures.

You won't see a measurable difference between a 90gr TNT from either 6.5 Grendel or 6.8 SPC in HD at close range looking at terminal ballistics.  They both frag immediately and don't overpenetrate.  One is .007" wider than the other before impact, one has a longer ogive for more expansion potential.  MV is the same on both from the same barrel lengths.

The Grendel just does multiple duties really well, making other chamberings specialized and reduntant, while not offering the other benefits of 6.5 Grendel, particulalry when looking at hunting and intermediate range shooting with an SBR.

So this doesn't come off like a baseless generality, just to show what I mean in being good at other things, an 11.5" Grendel with a 129gr Nosler ABLR smokes a 20" AR15 from the muzzle on out in every parameter except trajectory, which will always be flatter with a lighter bullet going much faster.

The SBR Grendel has more energy at the muzzle, and less wind drift than the 20" AR15 spitting a 77gr Mk.262 at 5.56 pressures.

It has less wind drift, and retained energy only gains on the 5.56 hot load from the muzzle on out.  It also has more energy at 400yds than a 20" .30-30 has with a 150gr at 200yds.

11.5" 6.5 Grendel 129gr ABLR 2250fps, BC = .553 G1 Litz, expansion thresh is 1300fps, at full expansion, it goes over .60 cal
Muzzle 1450ft-lbs
400yds 1704fps 832ft-lbs 1 mil drift

20" 5.56 .223 Wylde, 77gr Mk.262 Mod 0, 2785fps, Litz BC = .371
Muzzle 1306ft-lbs
400yds 1878fps 587ft-lbs 1.1 mils drift

20" barrel, 8ksi+ more chamber pressure, and 525fps more mv gives you wimpy impact, more wind drift, limited hunting potential.  You would do better in competition even using an SBR Grendel over a 20" .223 Wylde because of wind drift.

6.5 Grendel SBR suppressed is really the pinnacle of AR15 capability.

Recently it's been CCI 64gr Gold Dot for my 16" carbine.
It's backed up by 5 rounds of 12G Federal 00 Tactical Buckshot shells.
If all else fails l have 4 rounds of Winchester 1 oz slugs on the sidesaddle.

Double Ought Buck and a cleanup crew. Or a call to Winston Wolff

If you want suppressed, you want 300bo. 

6.5 or 6.8 reduce mag capacity for not much gain at short ranges for home defense.  I'm not going to trade more ammo/less recoil for more range when I don't need more range. 

I think 6.8 is the most most lethal of the bunch, check out lone star boars on YouTube. He's got a bunch of videos killing hogs with suppressed 12" 6.8s. Seen 300BO used even out of 16" and not nearly as impressive. 120gr sst or 120gr Cavity Back would be devastating

5.56 mk262ish OTM for less penetration.

Not really worried that it's not strong enough to lay an invader out

I think the discussion of 6.8 and 6.5 is irrelevant, but 6.5 wins as has been explained already. 

If you're talking home defense, you're thinking in tens of yards, not hundreds. You're also talking close quarters. You want it to be suppressed, which makes sense in such a situation. In my mind, the absolute best tool for this job is the most potent semi-auto rifle in the shortest package available. 300blk really allows you to maximize the platform out of the shortest barrels. A 7.5" barrel with a 6" can is going to be the length of a 12" sbr with a birdcage, but suppressed. If you run an Omega 9k, then you'll sacrifice some suppression for another inch+. That's about as short as the platform gets. Most calibers aren't available in such short barrels without getting custom work done. 

You are well acquainted with the abilities of the 300blk if you're killing hogs with it. It is plenty of bullet for down the hall and across the living room against some jerk (or jerks) intending to do you or your family harm. Plus you have 30 of them on tap and you're not going to be deafening or disorienting yourself every time you pull the trigger. 

For other purposes, you're likely better off with some of the other calibers you mentioned, but for extremely short barreled, suppressed, short range situations, I think the 300blk is exceptional. No need for one gun to rule them all... just have a gun for every occasion. 

Here is my bedside nightstand pistol... put together specifically for HD in the middle of the night or whenever. 300blk, 7" barrel, Omega can, Maxim brace. I don't do anything else with it (other than shoot occasionally to make sure it functions). I have other rifles for hunting/plinking/etc. 

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You're AR doesn't come out andcrest next to your bed when you're home at night? :). Mine does because I'm usually fondling it anyway and it just ends up next to the bed.

Sig srd and adj. gas block take care of gas.