Tactical difference between a carbine / "CQB" carbine and a SMG?

[simonrichter]

I'm well aware of the technical differences between (super short) carbines like the MK18 (it still seems kinda awkward to me calling these "AR psitols", though I'm aware of the legal reasons for that nomenclature) and SMGs like the MP5 or the UZI, Mac etc. To be exact, there is even a third "class" of weapons to be taken into consideration, namely the PDWs like the P90.

Are there any actual differences in terms of tactical use and value in military and LE operations or is that simply a matter of preferences? E.g., are there any considerable differences in terminal performance between a very short barreled .223 carbine, a 9mm SMG and 5,7mm or 4,6mm "PDW"? I reckon e.g. the muzzle energy advantage of 5,56mm over9mm becomes negligible out of such short barrels...?

[Fishbed77]

The muzzle energy and terminal performance of 5.56x45mm (when mated to proper bullet construction) is essentially always going to be superior to 9x19mm, even with short barrels.

Which is exactly why you see pistol-caliber subguns falling out of favor compared to short-barrelled carbines chambered in 5.56x45mm. The carbines are just far more versatile.

Now other issues such as blast and noise arise from these short-barrelled carbines, but the increasing prevalence of suppressor use is doing much to offset this.

[ttarp]

There are different and overlapping "tactical" applications for both SMG's and very short rifles.

A 9mm is less likely to cause a lethal friendly fire incident in a room clearing situation, and the short .223's will always be more lethal and provide more effective fire at range.

The problem with the noise is an issue thats only partially solved with suppressor use, since you lose some of the small handiness of the short rifle its a trade off.

[simonrichter]

What I find puzzling is that still there are a lot of 9mm carbines, even AR style, on the market. I take it the advantage oft these does merely depend on ammo cost?

[Fishbed77]

A 9mm is less likely to cause a lethal friendly fire incident in a room clearing situation, and the short .223's will always be more lethal and provide more effective fire at range.

Today, this is essentially untrue with proper bullet selection. Modern 5.56x45mm defensive ammo exists that is far less likely to over-penetrate than most common 9mm loadings.

http://www.tactical-life.com/exclusives/9mm-vs-223/2/

What I find puzzling is that still there are a lot of 9mm carbines, even AR style, on the market. I take it the advantage oft these does merely depend on ammo cost?

There are several advantages to 9mm carbines vs 5.56mm:

-Cheaper ammo.
-Typically less noise & blast vs. 5.56x45mm when shooting unsupressed.
-Typically less recoil.
-They are fun.

I own a 9mm AR-15 carbine. It's a lot of fun. But for defensive use, I'd always steer towards 5.56x45mm.

[rickyrick]

.223 blast from a short barrel inside an enclosed space isn't the greatest experience in the world. The sound is one thing, smoke is another.

Power wise, the 5.56/.223 is the hands down winner and I'd choose that.
I can also appreciate the advantages a lower powered caliber like a 9mm in tight spaces.
I'd revert to my pistol as a civilian home owner.

[alaskabushman]

From a civilian standpoint I don't think an SMG vs. a carbine would be much difference for something like home defense. They both would work well for defense and both would be deadly.

The reason the military has moved away from pistol caliber SMG's (with the exception of some specialized units) is simply the fact that rifle carbines are more flexible, more powerful and can be used at longer ranges.

SMG's came into their own when battle rifles were on 10lbs plus side of things, and had a fairly low rate of fire. While some SMG's were heavy (STG 44), they had a much higher rate of fire and low recoil.

Now with modern rifles/carbines, the rate of fire advantage is gone, the weight has lessened dramatically and carbines tend to be more accurate at longer ranges.

If you like a pistol caliber carbine or legal SMG then go for it, they are fun and cheap to shoot compared to their rifle caliber brothers.

[ttarp]

Today, this is essentially untrue with proper bullet selection. Modern 5.56x45mm defensive ammo exists that is far less likely to over-penetrate than most common 9mm loadings.

If I was talking about wall penetration I would agree with you, I was convinced by a thread here some time ago, but I'm suggesting a few rounds mistakenly fired into a friendlies body armor are less likely to be lethal with a 9mm.

[Fishbed77]

If I was talking about wall penetration I would agree with you, I was convinced by a thread here some time ago, but I'm suggesting a few rounds mistakenly fired into a friendlies body armor are less likely to be lethal with a 9mm.

By that logic, they are less effective on a bad guy as well.

Another reason why 5.56x45mm carbines are proliferating at the expense of 9mm subguns.

[deadcoyote]

I know this is a pretty rare or unique situation, but I could see the usefulness of a 9mm carbine simply based on my living where it rains ~100 inches a year and you can only shoot pistol caliber long guns at the indoor range.

[Theohazard]

Originally Posted by simonrichter

What I find puzzling is that still there are a lot of 9mm carbines, even AR style, on the market. I take it the advantage oft these does merely depend on ammo cost?

There are several advantages of a 9mm carbine over a 5.56 one, and those advantages help fuel the popularity of those pistol-caliber carbines. Here are the advantages that I can think of:

1) Lower ammo cost.

2) Less muzzle blast.

3) You can shoot it at more ranges (some ranges limit you to pistol calibers, or charge you extra to use their rifle-caliber bays, or make you go outside to shoot rifle calibers, like deadcoyote noted).

4) Ammo interchangeability with your handgun, and sometimes magazines, too.

5) If you're building an SBR, you can make it shorter than a rifle caliber; the action is slightly shorter on a pistol caliber, and some PCCs are designed with the mag well in the grip making it even shorter, something you can't do with a rifle caliber. Also, the 5.56 starts to drop off sharply in effectiveness when the barrel is shorter than 10", and the muzzle blast increases greatly as well. Whereas a 9mm doesn't lose anywhere near as much velocity when you shorten the barrel and the muzzle blast doesn't go up much.

[T. O'Heir]

"...Tactical difference..." No such thing as a 'tactical' anything. There is a logistical reason for a troopie to be issued a carbine or an SMG though.
SMG's, typically, are/were issued to vehicle crew, rad ops, officers and other people who need to use their hands for other jobs.
Carbines used to be issued to the same types, but now are mostly issued because they're light. "CQB" is a marketing term. It's a carbine.
"...the UZI, Mac..." Former was dumped due to its excessive weight. The latter has never been an military or LEO issue thing.
By strict definition, there's no such thing as a 5.56 SMG. An SMG uses a pistol cartridge. An M16K is one(Friggin' things shoot really well. Just an 9mm M-16.). An M4 is not. Am M4 is a carbine. Same cartridge as the standard PBI rifle in a shorter firearm.
An STG44 isn't(wasn't) an SMG. It's an assault rifle. One of exactly 2 such things to ever exist. It and the AK-47.
"...9mm is less likely to cause a lethal friendly fire incident..." Um, no. That has nothing whatever do with the cartridge used. And due to their length, SMG's, when they were common in the military, were involved in far more "accidents" than rifles or carbines. FNG's will turn away from down range with a loaded SMG in their hands more often than with rifle or carbine. Buddy of mine had a Sterling pointed at his middle, long ago, by an FNG. Absolutely nothing to do with the chambering though.

[Theohazard]

Originally Posted by T. O'Heir

No such thing as a 'tactical' anything.

Of course there is. Just because the word is often overused and thrown around haphazardly as a marketing term doesn't mean it has no real meaning. The word "tactical" does have a valid use and meaning, even today.

Originally Posted by T. O'Heir

"CQB" is a marketing term

Sometimes, but it's also a completely valid term. It stands for "Close Quarters Battle", and it's a term we used all the time in the Marine Corps. It simply means just that: Using a weapon in close quarters.

[James K]

Sure, and maybe someone can explain "tactical" undershorts. Sounds silly, but it has been used for the same reason anything else is called "tactical" - to sell it to the suckers.

Jim

[simonrichter]

Using the term "tactical" I simply wanted to express something like "other than logistic or price related"
Thanks for the interesting replies, though

[simonrichter]

Edit: I took the effort to actually calculate the muzzle energy of both 9mm and .223 out of a 10" barrel. The .223 has indeed a slight advantage over the 9mm of something around 1000 vs. 750 joules

Especially with 9mm +P, the difference becomes smaller when the lenghts go down to around 7" or 6" (ca. 800 vs. 650 joule)

With a barrel length of 5", .223 loses against 9mm with around 500 vs. 650 joules.

Out of a 3" barrel, 9mm wins hands down.

Of course it is hard to compare because there are so many different ammo types to take into account and also the fact that there are no real life data e.g. for .223 out of a 5" barrel (source: ballisticsbytheinch.com)

Sorry for the metric measures, ye imperial folks

[Rob228]

Inside of a house I'm perfectly comfortable with my 14" M-4.

Taking down a nautical vessel..... Well it is a nightmare from any angle, but that is where I would lean very heavily towards an SMG

[44 AMP]

"Tactical" is one of the most overused and misused "hype" words of the current era.

Tactical is a method of operation, NOT an item, no matter how cool it looks.

40 some odd years ago, when I was in the Army, we had two modes of operation, tactical and administrative. When we went on a field exercise, we were "tactical", meaning behaving as if in a combat environment. (digging foxholes, and sitting in them night & day, wearing all our gear, carrying our weapons, even being "attacked" by aggressor forces, all that fun stuff)

The last day of each exercise, we went "Admin", cleaning & packing up all the toys to return to garrison. Fatigues and soft caps, no perimeter guard, etc.

Tactical differences between an SMG, a carbine, and a CQB (whatever that is)? I see none. The function of all is to provide a weapon of shorter length than the standard infantry rifle, to be handier in tight spaces. Some designs do it better than others, ALL have sufficient power for close combat.

The added easily useable range of the 5.56mm over the pistol rounds means added flexibility of use. That's all.

One of the main reasons you see the military and police (who are being supplied by the military) using AR carbines (select fire) over 9mm SMGs, is COST. Not just the cost of the ammo, but the cost of the entire weapon system (the guns, repair parts, training, etc.)

Since the 5.56mm does at least as well as the 9mm in CQB, why spend extra money maintaining a weapon system that is (as now seen) not needed?

[DPI7800]

. police (who are being supplied by the military)

Wow news to me! I must be some kind of chump and been buying all my own gear all these years. I guess I need to go to the closest military base and go straight to the quarter master and demand to be issued all my high speed low drag military gear.

Can you quantify that?

[rickyrick]

Some departments have been supplied weapons and gear from the military. Just google 1033 program...

It has been quite controversial, inventories were published in newspapers

[random guy]

Especially with 9mm +P, the difference becomes smaller when the lenghts go down to around 7" or 6" (ca. 800 vs. 650 joule)

One more reason the .300 BLK exists:

7.5" barrel, 110 gr. bullet, 2013 fps, 1342 joules energy (990 fpe).

[ronl]

The caliber. I agree with 44amp. There is no such thing as a "tactical" weapon. Just a word that sounds cool when attached to anything from clothing to weapons.

[ttarp]

Are there any actual differences in terms of tactical use and value in military and LE operations or is that simply a matter of preferences?

I think the tactical horse has been beaten dead a long time ago, how about actually addressing the op's question? Just a suggestion.