Having recently begun my AR-9 build I’ve been seeing references on AR specific forums that 223/5.56 (55gr) out of a 7.5” barrel is equal to or performs better (terminal effects) than 9mm (115rg) fired from a 4”-7.5” barre at 0 to 25yrds.
I thought I’d pick the ballistic gurus here what their opinions are on this topic.

The argument is that at that range a 55rg .223/5.56 still has the velocity to stabilize in flight and tumble upon impact.
Giving it better terminal effect within 0 - 25yrds, than a 9mm .


I already have a 7.5” 5.56 so I was really intrigued when I came across this .


Opinions ?!?!



AR-9





7.5” 5.56

I can’t find data to provide an exact answer about the different ballistics performance of 9mm in longer barrels and 223/5.56 in shorter ones, but based on my own tests and what I could find it’s possible to get a general idea.

In my own testing, from a 7.5 inch barrel M193 (55 grain FMJ) has a muzzle velocity of about 2235 fps and therefore generates about 610 foot-pounds of energy. According to some opinions 2000 fps or greater is necessary to produce a temporary cavity capable of causing significant wounding effects. (I’m not convinced of that myself, mostly because I doubt it’s anything more than wishful thinking, but neither can I refute the claim.)

There are countless 9mm Luger loads, but if we use one reported figure for 124 grain Gold Dot Short Barrel, from 7.5 inches it should run about 1320 fps and produce muzzle energy of ~480 ft-lb.

If we decided only on the basis of pure kinetic energy and, possibly, the effects of any temporary cavities, then the M193 would be the clear winner of those two. What I don’t know, however, is how much penetration the two loads would achieve. In addition, both cartridges are available in many other loadings. The 9mm Gold Dot Short Barrel is far from being the hottest load available, and I’d expect something like the Gold Dot 124 grain +P load to do significantly better from 7.5 inches, possibly in the 570 ft-lb range.

On the other hand, the 223 Hornady 75 grain SBR load is specifically designed for short barrel use, and according to one article, it runs about 1950 fps from 7.5 inches. That’s 633 ft-lb of energy, but it reportedly penetrates well beyond the minimum of 12 inches recommended by the FBI when fired from 11.5". If I were limited to a 7.5 inch barrel in a defensive weapon, I would definitely prefer that load over 9mm. (Neither is close to being as good as what can be achieved with a cartridge like the 300 Blackout or when using a reasonable length long gun barrel, but that’s not what you asked.)

Leaving aside the huge flash and sound issues of unsuppressed very short barreled AR's the data I've seen for fmj rounds(for m855 not 55g109 since nobody uses it) says that to get 2500 fps you need 10" of barrel length. And that's generally the agreed threshold value.
But you and I can use better stuff than M855 or 109 and some of that is moving pretty close to its threshold range even in short barrels. You would have to research what you use to figure it out.
But me personally I'd consider 10.5 the minimum for effectiveness of 5.56.
Edited to add, all things being equal in terms of barrel length I would take 5.56 over 9mm every time, but for sure I would make sure the ammo I was using was going to get the job done in terms of terminal effectiveness, which might limit the options.

Federal fusions have good terminals down to 1700 FPS. Also, 556 233 will work vs body armor where 9 mm will not.

I have the 10.5 AR pistols covered.
Two in 300blk (FDE) & two in 5.56 (black) and in the past, when I traveled in the motorhome I always took the two 300’s.
Now I’m just playing with the 7.5” (5.56) and the yet to be built AR-9.
However I was interested in the answer to “what if I wanted to use either of these for personal defense”?
But while reading up on the 9mm ARs as well as “short ARs” I noticed there was a lot of folks dismissing the 9mm in an AR platform and stating the preference of a 7.5” 5.56 over them.
Which I don’t really understand since so many on here have dismissed the 7.5” 5.56 as worthless or a range toy at best.
My mind says if a 4” barreled 9mm pistol is considered a good choice for personal defense then why does that opinion seem to change when it’s in an AR platform?
Or does that not change but is it simply bested by the 5.56 in 7.5”?
I’m wondering if personal preference comes into play on this as opinions , even from folks from whom I’m happy to defer to seem to not be in agreement.
I’m happy to listen & learn all I can I ask these questions because I don’t want to be the guy who has already formed his opinion and is just looking for a source that will confirm it.


The Hornady 223 75gr sounds interesting.
I’m also interested in whether hollow points will feed well in my AR-9.
Sadly I don’t have a chrono but as these type of questions keep bouncing around my head I’m leaning towards getting one.

quote:

Originally posted by GrumpyBiker:
Or does that not change but is it simply bested by the 5.56 in 7.5”?

That would be my reasoning if I were considering a 7.5" AR.

I believe that the oft-heard platitude that handguns are poor self-defense weapons is arrant nonsense, but for me it’s a question of what’s best in a particular weapon. Even though the 223/5.56 cartridge loses much of its ballistic effectiveness at lower velocities, based on my research in considering your question, it’s nevertheless evidently better for the purpose than the 9mm cartridge even out of a longer than normal barrel. If two different types of guns were being considered for various specific purposes, that might possibly change my opinion, but that’s not what you’re considering.

Every decision relating to self-defense weaponry involves compromises, but my philosophy about the subject is to reduce their adverse effects as much as reasonably possible. Some people might believe that the muzzle blast of the 223 from such a short barrel is enough to settle for less wounding effects, and if that’s their considered opinion, that’s their choice. In the very unlikely event that I will ever have to use a gun for defensive purposes, however, I will want whatever shots I might get off to be as effective as possible (within the limits of the other compromises I’ve made).

First I've not had any issue feeding anything out of my Colt 9mm AR's. hollow points and a zillion other types of ammo. if it fits in the mag it runs. Other setups YMMV.
But if I could get it I would be using 75tap sbr out of any 10.5" 5.56 and be really, really happy. Passes the full FBI protocol. A 7" AR I'd be looking for a specific test on a specific ammo and not be happy till I see that its GTG.
And in the scheme of things the barrel difference to 10+ seems not meaningful to me. (mine are factory colt so 10.5, but OK YMMV).

I dont have any info, but I really want to build a 223 pistol even if it's a range toy. those are cool.

I think the whole "temporary stretch cavity" nonsense is gunwriter bullshit. I'm much more interested in penetration, or the actual wound channel, not a temporary displacement that looks neat in gelatin, but isn't necessarily significant otherwise. Gel doesn't displace and move back; tissues do. If the tissues are ruptured and bleeding or can't function, that's another matter. That matter is the actual wound channel.

All things being equal, higher velocity, higher sectional density, and greater weight are going to penetrate further, expansion really coming into play largely to prevent overpenetration. Any additional enlargement of the wound channel (actual damage, vs. "stretch") is a bonus.

Muzzle energy is not the only standard, but on that basis, 9X19 is hard pressed to be pushed much past 500 ft/lbs with a 7" bbl. It can be squeezed up there in hot loadings with +P, but isn't going to exceed 5.56 or .223.

http://www.ballisticsbytheinch.com/9luger.html

5.56/.223, on the other hand, is suffering substantially from losses by the time it gets to a 7" bbl, but still exceeds 9X19. Whether the bang and the flash are worth it, is another matter. 10" is plenty short, and really what are you going to do with a 10" bbl that can't be done with a 14.5 or 16" bbl?

You can pump up the ammunition and squeeze a bit more out of it, but it's like running .357 in a 2" bbl...the round is handicapped by such velocity loss that it's nearly at a point of diminishing returns, and I think you'll do better with some of the pistol cartridges by the time you get into a sub 10" barrel.

http://www.ballisticsbytheinch.com/223rifle.html

At the risk of hi jacking this thread, where would a 300 Blackout pistol fit in relative to the 9mm and 223 AR pistols you are comparing? I’m considering the Blackout right now, so this comparison is of significant interest.

Energy really doesn’t matter (directly). It is going to come down to the specific projectile. A 5.56 FMJ that doesn’t tumble or fragment would probably be worse than a good expanding 9mm HP. OTOH, a bonded SP like the fusion or copper TSX that is proven to expand in that lower velocity envelope would be superior.

Id like the .300 BLK better than either with a barrel that short and a good 110g supersonic load.

Strambo, how long is the barrel on your Blackout?

quote:

Originally posted by Sourkraut:
At the risk of hi jacking this thread, where would a 300 Blackout pistol fit in relative to the 9mm and 223 AR pistols you are comparing? I’m considering the Blackout right now, so this comparison is of significant interest.

It sort of depends what role you want the Blackout for.

Very compact package with subsonic ammunition?

Go with something like an 8" barrel.

You gain some MV with supersonic ammo if you use a longer barrel.



Personally I tap out at anything shorter than 10.3 for a 223. The extra bit of compactness doesn't make up for the decreased terminal effectiveness and the drastic increase in blast.

quote:

Originally posted by IndianaBoy:

quote:

Originally posted by Sourkraut:
At the risk of hi jacking this thread, where would a 300 Blackout pistol fit in relative to the 9mm and 223 AR pistols you are comparing? I’m considering the Blackout right now, so this comparison is of significant interest.

It sort of depends what role you want the Blackout for.

Very compact package with subsonic ammunition?

Go with something like an 8" barrel.

You gain some MV with supersonic ammo if you use a longer barrel.



Personally I tap out at anything shorter than 10.3 for a 223. The extra bit of compactness doesn't make up for the decreased terminal effectiveness and the drastic increase in blast.

I’m thinking specifically short range home defense. Would BO be better than 223 or 9mm?

quote:

Originally posted by Sourkraut:
I’m thinking specifically short range home defense. Would BO be better than 223 or 9mm?

For a large, AR-style gun with short barrel, the 300 Blackout is far superior to either 223 or 9mm, IMO. The 223 cartridge is capable of causing horrific wounds due to the cavitation effects it produces (check the Internet for examples), but that’s when fired at carbine or better velocities. When fired from short barrels it doesn’t become impotent, but those effects are much reduced and its small, lightweight bullets don’t do the same things. And as is mentioned every time the subject comes up, there is the disadvantage of the muzzle blast of the 223 when fired from short barrels. An officer I knew had an AR with a short barrel and even with the attached suppressor the muzzle flash in low light was blinding.

One major factor of wound ballistics effectiveness is kinetic energy of the projectile. That’s why rifles are generally far more effective than handgun cartridges for hunting and other purposes when wounding is important. The advantage to me of the 300 BLK is that with supersonic loads it produces as much energy from short barrels as the 223 does from a 16" carbine. To cite just one comparison, the 55 grain M193 load from 16 inches produces about 1120 foot-pounds of energy. From my 9" MCX, the Hornady 110 grain V-MAX load produces about 1170 ft-lb of energy. The V-MAX bullet also expands and penetrates well at lower velocities. A hot 9mm load from a similar length barrel would produce about half the energy.

Would the 9mm from an AR-type rifle be effective for self-defense purposes most of the time? Of course; the cartridge is effective most of the time for the same purposes when fired from 4 inch or even shorter barrels. I personally cannot imagine limiting myself to a lower-power round, however, when the weapon I’m using is capable of handling something much better for the purpose.

There is, however, little advantage to using subsonic 300 BLK loads for any serious purpose unless it’s during a special ops mission to take out a sentry or guard dog.

So supersonic loads for a home defense round vs slower heavier weight subsonic rounds. What are your thoughts about over penetration concerns of the 110grn Blackout round vs 9mm and 223/556?

Subsonic loads in 300 Blackout generate kinetic energy levels similar to handgun cartridges. And although there’s nothing wrong with settling for handgun energies if we have no good alternatives, supersonic 300 loads are simply better if we want to cause the maximum damage to our targets.

It’s generally reported that heavy bullet handgun rounds penetrate deeper through building materials than light 223 projectiles. Part of that depends, of course, on the velocity and construction of the bullet. I found, for example, that the 64 grain Gold Dot bullet penetrates vehicle windshields better than the M193 bullet, but the M193 bullet penetrated the sheet metal better. Both did better against sheet metal than the 62 grain M855 green tip bullet.

I suspect that a bullet like the 110 grain V-MAX would penetrate through building materials more than most 9mm or 223 projectiles from similar length barrels, but I have no hard evidence to support my belief.

Thank you for those thoughts Sigfreund!

223/5.56 out of those 7.5 and 10.5 is really LOUD. I was at the indoor range the other day and a guy was shooting a 7.5” barrel AR. Since I shoot 357 Mags and 10mm I double up - military rubber ear plugs under good headphones. Trying to protect what hearing I have left. 357 Mag is loud, but it it doesn’t chase people out out the range. The AR pistol is somehow harder put up with than 357 Mag. Something about the frequency of the crack.

Good luck with your hearing if you shoot those AR pistols inside a building without hearing protection - like you would do if something ever went bump in the night.

+

I've shot a fair amount of Hornady 110 VMax ammo. No scientific tests in gel, but I've dug quite a few bullets out of dirt and sandy backstops. Distances were 50 to 100 yards, shot from an 11" barrel. The bullet expands pretty well -- maybe between 50% and 100% greater than bore size. I haven't seen complete separation of jacket and core, but the front edge of the jacket is definitely peeling back from the core. It appears the bullets lost very little mass -- meaning that they weren't fragmenting.

Vmax bullets are known for rapid expansion, and they probably do at 308 Win velocities. I suspect the 110 vmax at 300blk velocities penetrates further than it would at 3000 fps-ish velocities.

But 110 VMax isn't the only game in town. Hornady loads 110 GMX and 135 FTX, which almost certainly expand most slowly and penetrate deeper in most mediums.

Fiocchi loads Hornady's 125 SST, which is almost certainly a slower expanding bullet than VMax.
Federal loads a 150 Fusion, which is known as a game bullet. Also a 120 Power Shok copper solid bullet.

Corbon loads a 125 MPR bullet with a ballistic tip.

Barnes loads their VOT-TX copper solids in 110 and 120, which will penetrate well. I've dug them deep out of berms.