I have a short barrel AR, 7.5".

I really like the maneuverability and the weight.

However AFTER I bought it (of course) I started reading about it not having enough velocity for home defense or any other legitimate lethal use.

What do you think?

Should I go back to a carbine for room to room?

I'm assuming its 5.56.

If so then it will indeed be lethal. Depending on the ammo, it could over penetrate as well.

The decrease in muzzle velocity will cause certain types of ammo to be more devastating than if shot at a higher velocity within the same distance.

Personally, I don't use an AR for home defense. In a CQB situation there are much more effective weapons on the market. If your defending a property line then it becomes more ideal, in my opinion. To each is own though.

Basically, if you shoot someone, with your AR pistol, their not going to be very happy about it.

From the ammo section:





There's a few bonded defense loads that perform similarly.

While I have a 7" I like the 10.5" for the role as most anything works well at close range.

20140130_111347_LLS by Slick_Rick77, on Flickr

It's thirty rounds available with each having the same energy point blank as a 44 mag, with less penetration than a typical shotgun or pistol defensive load.

Good response and photos.

Thank you!

Keep in mind that with any firearm in a house over penetration "might be an issue". Depending on what the house is made of will determine if the bullet keeps on going or not. In an apartment complex rounds could go in the next unit.


Finetkind

In any case, if shooting unsuppressed inside a home with that 7.5" barrel, you'll quite likely disable any intruder by deafening him from the blast

With short barrels, 300BLK is a much better choice than 5.56. 300BLK has a lot less blast/concussion because more of the energy of the round is being applied to moving the bullet. It's going to have better terminal effect on the bad guy and is less likely to cause you permanent hearing damage.

My default HD gun is an 8" 300BLK.

A 7.5" can do the job with the right ammo. The question is one of priorities. The longer you go, the more ammo flexibility you have in 5.56. If you have to buy expensive ammo for a 7.5" 5.56, why not step up to a 6.8 or .300? Ammo costs will be similar.

If it's primarily a fun gun for range blasting, the 5.56 makes some sense, since you can shoot mainly cheap stuff. If it's primarily for serious use, the bigger caliber makes sense to me.

What usage requirements point to a 7.5" over a 10.3/10.5"? In vehicles? Super cramped home? Looks cooler?

The basic rule with 5.56 is that velocity is paramount. Smaller barrel = smaller ammo choice. And even rounds that perform acceptably out of a short barrel will generally do better from a longer barrel.

Except that temporary cavitation is significantly greater from the longer barrel. At rifle energy levels, this is a legitimate wounding mechanism.

For those concerned with who's apartment or house becomes the backstop for their bullets, map out your likely shooting lanes and give it some though beforehand. Since tactically you check and don't open the door to strangers - right? - then they have to beat it down to enter. Where will you position yourself and fire rounds, will they be sufficiently stopped by whatever becomes the backstop or is it' your neighbor's bay windows in the living room?

Same for the perps rounds coming back into your home. They are not choosing low penetration high expansion bullets - they shoot what they get and you deal with it. Do you need to adjust where your safe room is to prevent them shooting into your neighbor's bedroom?

Given those situations, what ammo you choose to use is only half of the problem.

What the military choose bears some thought, first, the MK18 went with a 10.5" barrel as the minimum length to get effective ballistics, and then the Mk262 77gr OTM was chosen with low flash powder as the complementary round in use with ship boarding crews, or operating in urban situations like Pakistani townhouses. Mk262 isn't as good as M855 in penetration but does the job.

Building a 10.5 myself, I would suggest considering the longer barrel and using the better ammo. But the tools are only half the point, their defensive use needs to be planned and consideration taken over where all the bullets may land.

I plan to chrono my 7.5" this weekend.  I'll let you know.   I think it's pretty lethal.

A 7.5" will do. Just make sure you have a linear comp on it to deflect sound away from you.

I use a Glock for HD because of maneuverability and concealment. It's kept in a hardened quick open safe that's easy to get to.

Linear comps are completely useless for redirecting blast/concussion indoors. Even if they direct it forward initially, as soon as it hits a wall, it's right back in your face. The only things that really help indoors are a can, or using a round designed for shorter barrels (lower uncorking pressure and less blast/concussion), or both.

Step 1: Look up the velocity range (in FPS) your chosen HD ammo performs best at.
Step 2: Look up the ballistics for a 7.5" barrel for that ammo.
Step 3: Compare to your uses/needs (typical distance) and compare to other barrel lengths to see if another length is better.

Now you will know what range your barrel/ammo combo performs best at, and what the penalty is for going with a short barrel. It should take you 10-20 minutes.

Yes a suppressor would be ideal. A linear comp is not worthless. It's better than a bird cage.

So name some ammo designed for shorter AR barrels.

Im planning a 10.5 300BLK build. But thats just my preferences. 7.5 seems too short to me.

If I used an AR for HD, I would use whatever they LLEA uses in their rifles.

You load or buy specific rounds, and in a world where the news was touting Zimmerman's gun didn't have a safety (Glock), and they'll say you were using super killer ammo or something.

That said, Zimmerman was acquitted, regardless of the yarn the lawyers spun for the media.

It sounds like there's a exponential velocity loss between 10" and 7". Less so from 14.5" to 10.5".

Zimmerman had a Keltec PF9

For those of you that have never shot a rifle indoors the concussion is ridiculous.  Shooting a 7" barrel outdoors with a linear comp is stilll teeth rattling.  The only true solution is a suppressor.  If a suppressor is not possible then I would probably use a subsonic 300blk out of a 10" barrel.  I haven't shot one but I'm assuming it's going to be the least concussion solution out of an SBR.   10.3 CQBRs were made to fit in the confined quarters of ship passageways.  If it works for them then I don't see any purpose in going shorter in a household.

Just my $.02

I don't go any shorter than 10.5 on my builds.

Wouldn't you get better performance out of a 7.5 with ballistic tip ammo.

Ballistic tip projectiles such as Hornady V-Max or A-max perform down to about 2000fps.

In my 10.5" build i keep a heavy predator/light deer soft point load. FWIW.

Outdoors in the open, yes. Not when shooting indoors where sound, blast, and concussion are enclosed. If there is a wall in front of you, it will bounce all of that back at you and completely defeat the function of any linear comp.

The only 5.56 round I know of that is designed for, and has decent terminal performance out of a 7.5-8" barrel is the Black Hills 50gr TSX. But it is going to have a lot more muzzle flash and blast/concussion than any 300BLK round.

I've fired 5.56 and 300BLK at night side by side, and 5.56 had more flash from a 16" barrel than the 300BLK did from an 8" barrel, even with both guns wearing YHM 5C2 Phantom flash hiders (the 300BLK was running the 30-caliber version obviously). The 5.56 gun fired green tip M855, and the 300BLK fired 130gr Remington Hog Hammer. The 5.56 had small flames that extended out from the flash hider ports an inch or two, The 300BLK had no flame at all, only has some dim orange sparks. The 5.56 was noticeably louder than the 300BLK, even though the 5.56 barrel was twice as long.

A 7.5" 5.56 AR pistol loaded with the Black Hills rounds would be effective on a bad guy in your house, but the concussion would probably be enough to break windows, and pop the eardrums of the perp, you, and anyone else in the room not wearing ear protection. An unsuppressed 300BLK with a similar length barrel isn't going to be "hearing safe", but is going to be far less likely to cause permanent hearing damage if fired indoors.

An AR pistol with a 7.5" barrel and M193 ammo will get the job done extremely well. This is the setup I have.

Anything in a standard pressure cartridge firearm hurts the ears indoors. Guns are loud.

A window could break...if the muzzle is against it while firing

What is the velocity at 7 to 25 feet?  Bet you it has plenty, if not I'll be glad to dispose of it properly for ya.



 

Under 2500fps, which is the fragmentation threshold for standard 55gr ball. You need a 10" or longer barrel for it to work well. M855 requires an even longer barrel for effectiveness.

With 300BLK, you get a much more lethal round from short barrels, with far less blast, concussion, and flash. I have 8" pistols in both 5.56 and 300BLK and have compared them side by side. The difference in blast and flash intensity is profound.

Do a bit of research and see how many people are deer and hog hunting with 7-8" 300BLK guns vs 7-8" 5.56 guns, and what kind of success each group is having.

lol If you shoot an intruder indoors with a .5.56 they are going to be dead and/or deaf before they hit the ground.  You won't need to be worrying about velocity at those ranges.

You'll be deaf, too unless you're wearing earpro (not likely in most HD scenarios).

30 rounds of anything out of an ar is going to do the job.

So let me see if I understand you correctly... a linear comp is completely useless, but the round designed for shorter barrels that will really help is going to blow out windows and everyone's ear drums?

"round designed for shorter barrels" being a 300BLK...

you need a linear comp on that too

A 55-62gr softpoint or other expanding round traveling at 2200 fps or better is far from ineffective. Not to mention that you have 30 of them.

- OS

Exactly! Most hog hunt with 300 BLK for a reason not seen on paper. The 300Blk in a 10.5 " barrel is better. The 300blk does not lose as much velocity in the shorter barrels

 

I did a side-by-side comparison 5.56 to 300BLK, both guns with 8" barrels and the caliber-appropriate model of the YHM 5C2 flash hider. The 300BLK is not hearing-safe, but the blast/concussion is far more tolerable from the 300BLK than the 5.56. And a linear compensator does not help at all indoors when the blast directed forward hits a wall and bounces right back in your face.

This is my opinion on what I prefer if I knew I was going to have to shoot in self defense.   Like most people, I still reach for a traditional pistol most of the time as I am not expecting to have to actually fight.   I generally have a pistol for "just in case".      

I love the 5.56 and the AR.    I especially like the 20" A2/4 varieties.  I think they are great for fighting outside of heavily congested cities.     Having said that, I only have one like that, and it is all Colt except for the Geissele trigger.    I have 1 16" light weight, 1 14.5" government profile (M4gery), 1 14.5" short stroke piston, and a 16" heavy rig with a 1-4 Trijicon TR24R AccuPoint, while the other 3 wear Aimpoint Micros.   The blast of all of these even just under cover such as a shed is horrendous.   In a building or vehicle unsuppressed, it is God awful.    Still,  I see those as urban rifles capable of most needs.   Yet, for home defense, I even skip my 16" 9mm Colt Carbine AR and go for either a suppressed (SilencerCo Octane 45 HD)  7" 9mm AR wearing a Trijicon Reflex 4.5 MOA  ACOG  using 147gr HST rounds  or a suppressed (SilencerCo Saker 7.62)  8.5" 300 BO AR wearing a Aimpoint Micro.  The neat thing about the 300 BO is that you have a 45 ACP on 1 end of the spectrum and a 7.62X39 on the other end.     Not much is faster than the 9mm AR short of a NFA gun.   Many 9mm ARs even without a bumpfire stock will out run a M16.    (Remember, these are blow back ARs with very simple and slick triggers.)  9mm ARs are routinely very accurate.    People frequently  have more difficulty getting really good accuracy out of the 300 BO .    Either way, I far prefer the 9mm and 300 BO in a short barreled AR in and around the home, buildings,  and vehicles.

I have a lot of other guns, from pistols, and revolvers, to pump and auto shotguns, including one that is a combination of the 2, a Benelli  M3.    

I do prefer real MP5s over the Colt 9mm sub gun.  (Full auto VS Full auto)     But, I also prefer the 9mm AR over the HK 94.   (Semi VS Semi)    Strange?   Maybe.  But, those are my preferences.

The 300 BO AR can go both ways and perform as a good suppressed CQB gun or go into a more intermediate role like a 7.62X39.

If I were limited to unsuppressed fire for around the home, I would build the most wicked 9m AR that I could.   Actually, that is what I have done, but I also suppressed it.

I am not a Navy SEAL.   I am just a combat medic, combat engineer, recon team lead, and light infantry officer.   Everyone has to make their choices based on their education, training, and experience.  The biggest issue I have is that I have no combat experience with the 300 BO round in any load from any platform.  

In a self defense situation the last thing youre gonna worry about is your hearing.  Or keep a set of ear plugs by your AR if youre that worried about it.

This.

Accordingly,  it is critical to plan, in a practical manner well in advance, and train.    Putting in earplugs as you hear someone breaking open your storm door on their way to busting down your front door is less than practical.    On the other hand,  reaching for one of your suppressed ARs within arms reach of your bed is quick and extremely practical.  

Remember, during a fight is not the time to be planning how you will respond or what gear you be getting and using in training.    

Go with the platform you have used in classes since your teens,  trained with in the field, and had trigger time in combat.   This is be natural and fast.    The  last  thing you want to do is be fumbling around with things, especially tiny little earplugs.  

I fired an entire 100 rd belt from a 7.62 M240G machine gun with no hearing protection and fired fifty rounds of 454 Casull out of a ported barrel indoors with inadequate hearing protection in close time frames. There was no measurable hearing loss.

The hearing thing is a bit overblown. It's painful afterwards but you don't even know your ears are taking a beating during. Don't make a regular habit of getting into gunfights indoors and you'll be okay. Most overblown topic ever

I fired M16s, M4s, M1911s, and  M9s indoors, along with M60s under cover, all with little to no hearing protection.     I had to.    

I have also blown a lot of stuff up.     My hearing is severely damaged.

I could end up firing a pistol indoors or inside of a vehicle, unsuppressed.     I  really hope that doesn't happen.  

I do have choices.    For me, I am reaching for a suppressed 9mm or  suppressed 300 BO  AR for home defense.  

I know some people who were born male and love to take it up the tail.    I am fine with them doing that.   That is their choice.     BUTT, I as sure as the Devil am not doing that.

Good for you, man!

In a Hd role.... I don't think 7.5" or 10.5" will make a difference... 30rds of 556 or 223 ammo will put down the intruder. With that said, keep an electronic ear protection next to whatever gun you choose. Not only will it protect your ears, you will be able to listen better!

No doubt the .300 is good in an 8" barrel. The ammo costs practicing at a range, not so much. And training ammo is the major expense. This is why I went 5.56 - I can shoot cheap fodder at torso targets all weekend, and then use the 77gr OTM as the defense load.

As for noise, it's a problem regardless of the cartridge or barrel length. A silencer is nice to have, it does control muzzle blast especially when working closely together in teams. Not so much in some states if it's illegal, and the expense is high.

There is an alternative to silencers, it's used everywhere, including in teams where silences are issue. There are more units sold every year by just one vendor than the total sales of silencers overall.

Electronic mufffs Especially the better grade ones with good circuits and amplification. Look at the next range competition and see how many active muffs are on the line. They aren't cartridge dependent, one size fits most, and THEY SUPRESS THE PERP'S GUN TOO.

You can spend all you want on your silencer, the perp isn't bothering - he has you downrange of his blast regardless.

If you can leap fully awake to grab your MK18 clone and start clearing the rooms in your jammies, having sound suppression on your ears with the added benefit of low sound amplification is a major benefit. Which is exactly what the teams ARE doing.

Think about it. Muffs for $100 street price (Peltor Sport Tacs) vs. $200 for Stamp, $200+ for trust, and $$$$ for silencer, all to fix just your gun alone - not theirs.

Already on my build list, as much an necessity as a flash hider or optic. And I can use them for yard work, chain sawing, and hunting.

In a defensive situation you'll barely have time to get to your gun let alone fiddle dick around with hearing protection. I say screw my hearing. I want to live. Immobilize the threat and worry about everything else second.

Any of you guys reload? Just pop a cap inside and see how loud that is. You'll get the point. Multiple rounds of anything is friggin LOUD!

Brad

I wonder what the effect of using a varmint-style selection of barrel and ammunition would  have to solving the barrel length based fragmentation problems of regular issue ammo.  It would be interesting to see what some of the high dollar prairie dog rounds would do to ballistics gel out of a 7.5" Ar  pistol with 1x12" twist.

The gun for the man who killed too many prarie dogs.............and they've found him

If you're looking for a cheap flash-bang grenade then 5.56 from a 7.5" will do nicely.  If anyone else is in the house you probably just made them deaf, and yourself as well if you aren't wearing hearing protection.  Nevermind the God-awful flash.  Flash-hiders be damned.  In the dark the white walls, ceiling, and everything else will bounce light just like sound, so you've incapacitated yourself when you are full defensive.  Go Blackout all the way in this scenario.

So you shoot the FIRST guy, have no idea the second is there because you can't hear $4!+ now ,and take a knife from behind... This mindset is beyond dumb.  Am I the only guy that has thought to keep a pair of electronic ear muffs hanging off my magazine?  It's 2 seconds to put them on and turn them on.  That means when the bangs come the BAD GUY will be deaf and at the disadvantage now, not me.  God gave us ears for a reason, protect them.

I disagree. Firing a short bbl AR (or any rifle for that matter..) in a closed space is analogous to a grenade going off next to your head. It's disorientating and takes you out of the fight momentarily. Furthermore the flash of a shorty in a dark environment is also very disorienting and will defiantly slow you way down, blind you momentarily (for a while actually....) and fuck your day up if you're trying to fight and survive.

I'd strongly recommend that anyone considering a 7.5 5.56 AR for any type of general purpose HD reconsider their decision.  Ballistics suck, though the newer rounds are more effective than ball they suck as well.

My choice in the house  is a G-34 with tac light and a 32 round mag as a primary and a 8" 300 AAC shooting 220 subs with a can on it as the "go to" rifle, if needed.  I used to keep a claymore bag with some extra mags, a few flash bangs, some flex cuffs, etc...next to the bed as well but not so much anymore.  The pistol is fast inside tight spaces and allows for tight clears without getting jammed up such as in closets, bathrooms, etc...pistols, unsuppressed, are loud indoors but manageable.

The 300 shooting 220's has enough energy to get the job done and is perfect with can indoors, both in terms of flash and sound mangement.  

In any case whatever you decide I'd strongly recommend that you shake out your kit as realistcally as possible to get a sense as to how it all performs under real use. You might be very surprised what a 7.5" AR sounds  like in a bedroom and what the flash can do to non-light adjusted eyes.  You'll be blind and deaf for what seems to be an eternity....and that's a hell of a way to fight for your life.

This has been my experience. When shooting without ear pro (which is of course not recommended), you don't notice how loud it is until a half-hour later, when you notice your ears ringing. You don't lose hearing at the time. It's not like a jet engine, which presents a constant stream of earsplitting sound that drowns out everything else - gunshots are loud sounds with a short impulse.