What is the shortest PRACTICAL barrel length for .223/5.56 AR

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BSA1

BSA1

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What is the shortest PRACTICAL barrel length for .223/5.56 AR-15? By practical I mean reliable functioning with 55 gr. FMJ without using custom barrel, gas block or specialty ammunition. In other words how short of barrel can be used in a SBR / Pistol using commonly available off the shelf parts?

(For this discussion a SBR is merely a pistol with the butt stock added.)
 
I had personal experience with a Radical Firearms 10.5 Nitride carbine gas that ran flawlessly with M193 in a budget mil-spec build. The gas system length will play a part, and I am sure others will have good luck with shorter length, but this was my experience.
 
If your bar is reliably functioning then it would generally be 10.5” inch. I know that BCM has a thing with 11.5” inch (and those work great), but I haven’t had any issues with 10.5”. Below that it’s a case of sometimes there’s issues and sometimes there aren’t.

If you're asking about the fragmentation from that FMJ then the shorter barrel you go with the less likely it is to fragment depending on the distance of the target you’re engaging.
 
When you say “practical” that implies terminal ballistics matter. Your choice of 55g fmj (my fav) is good but relies on velocity to fragment rather than just expanding like most rifle bullets.

The drop in velocity is significant when you get below 16”. From memory (somebody check me) but even at 10.5” (what I use) the m193 only reliably fragments out to around 150m or so. When you drop to 7” it is significantly less.

Also typically the noise increases dramatically.

If you just want a range toy or plinker that doesn’t malfunction much, then like varmint said, it can be done. But practically there starts to be a very narrow range of use cases for which a 10.5” or shorter barrel is most appropriate.
 
BSA1 said:
No one has experience with or uses AR with barrel shorter than 10.5"?
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Yes, 7.5” and an 8.5”.

The 8.5” ran okay (although over gassed) and the 7.5” had extraction issues. I’ve had a multitude of friends also build them, some ran well and others not so much.

IMO if you’re going under 10.5” inch (i.e 7.5, 8.5 or whatever) then extreme care in picking which AR upper you’re going to go with is essential. The complete uppers seemed to be more hassle free.

If you’re building an upper from parts choosing which parts are going into the build should be escalated even more. It’s not like with a 16” or 20” inch where just about any upper you slap together with okay parts will likely work.

They’re a little finicky. Hence the sometimes they work and sometimes they don’t. :Shrug
 
For me, the shortest practical length for a 5.56 AR is 11.5" with a carbine length gas system. I've made a 10.5 run without doing anything exotic, but after shooting both, I find the 11.5" has less drop at 300 yards and enough more velocity to make the extra inch worth it.

Many with combat experience prefer the 12.5" over the 11.5" because they say it gives them better terminal ballistics with military rounds, more reliability and is handier than a 14.5" barrel. I haven't had any reliability problems with an 11.5" barrel and I shoot it a lot suppressed.

If you're looking for the easy button for a good shooting shorty, start with a Colt 11.5" barrel. Or, see what Black River Tactical is offering in that length. Both barrels have the right size gas ports. Use an H2 or A5H2 buffer for softer, smoother felt recoil.

PS- If you don't use a suppressor on your shorty, get an inline compensator. I have personal experience with the BRT Covert Comp. It's lightweight, small, affordable and it works.
 
BSA1 said:
What is the shortest PRACTICAL barrel length for .223/5.56 AR-15?
Click to expand...
An AR15 in 7.5 can work just fine but it's the absolute minimum. You need to know what you are doing since they a picky with ammo and port size.
The 10.5 is a lot more common since it provide more reliability and better performance than a 7.5 (MK18 with 10.3)
The 11.5 (My favorite) even better performance than 7.5 and 10.5 while been shorter than a 14.5. Softer recoil, and great for suppressors. it's the grand daddy of the MK18 back in the (Colt Commando and XM177) days.
The 12.5 is also great like the 11.5
The 14.5 is standard issue M4 it's an all around length that work great as a rifle.
The 16.5 (civilian version of the M4)
The 18" (my favorite when it comes to DMR)
The 20" (Standard issue M16)
 
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I’ve had a 7.5 and it functioned just fine I have 4 in 223 in 2 in 7.5 and 2 in 8.5 all functions just fine.
 
taliv said:
When you say “practical” that implies terminal ballistics matter. Your choice of 55g fmj (my fav) is good but relies on velocity to fragment rather than just expanding like most rifle bullets.
Click to expand...

Not concerned about fragmenting. I want reliable functioning and a reasonable degree of accuracy at 25 yards using basic 55 gr. FMJ such as PMC Bronze, Federal M193 and other bargain ammo. Once I have that then I can work on finding mission specific ammo.

taliv said:
The drop in velocity is significant when you get below 16”. From memory (somebody check me) but even at 10.5” (what I use) the m193 only reliably fragments out to around 150m or so. When you drop to 7” it is significantly less.
Click to expand...

That is why I specify 55 gr. FMJ. My concern is not about downrange bullet performance as having the gun first perform without having to do a lot of experimenting to find a brand that works.

taliv said:
If you just want a range toy or plinker that doesn’t malfunction much, then like varmint said, it can be done. But practically there starts to be a very narrow range of use cases for which a 10.5” or shorter barrel is most appropriate.
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It will be shot mostly on the range but that is not the real reason I want one. The real reason, although legal, which hopefully will never happen is not permitted for discussion on THR. I will let you read between the lines why I want to be able to use commonly available ammunition.

Browning said:
Yes, 7.5” and an 8.5”.

The 8.5” ran okay (although over gassed) and the 7.5” had extraction issues. I’ve had a multitude of friends also build them, some ran well and others not so much.
Click to expand...

Is adjustable gas block advisable?

Browning said:
IMO if you’re going under 10.5” inch (i.e 7.5, 8.5 or whatever) then extreme care in picking which AR upper you’re going to go with is essential. The complete uppers seemed to be more hassle free.

They’re a little finicky. Hence the sometimes they work and sometimes they don’t. :Shrug
Click to expand...

Finicky is at the heart of my question hence why I said practical. I don't want to get into the size of the gas port, etc. for it to function correctly. I am not really sure I want one but I want to check on what if anything I am missing. 10 ½” barrel is close to a SBR for me but I don’t (at least at this time) don’t want the expense and b.s. with the NFA.
 
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Have you thought of switching platforms my tavor is shorter than my 10.5 pistol or many similar to ar setups that don’t use a buffer tubes or even just get a folding hinge it’s a little on the pricy side but you can turn a 16in rifle into roughly the same length as a 7.5 pistol.
 
BSA1 said:
Is adjustable gas block advisable?

Finicky is at the heart of my question hence why I said practical. I don't want to get into the size of the gas port, etc. for it to function correctly. I am not really sure I want one but I want to check on what if anything I am missing. 10 ½” barrel is close to a SBR for me but I don’t (at least at this time) don’t want the expense and b.s. with the NFA.
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I’ve never actually used adjustable gas blocks on any of the AR’s I’ve owned.

So we’re getting outside of the area that I have experience in. I can only speak on the sub-10.5” AR’s that I’ve owned (none which have used adjustable) and the ones that have been owned by friends or family members.

Out of those only a few have used gas blocks for sub-10.5” pistols. Those were in vogue for a short period and then went out again. One came on it from the factory (Noveske) and the others were really well researched builds done by a guy that’s done quite a few (100+). All three worked great for what it’s worth. That’s really a sample size of two though (Noveske and the most experienced guy I know on AR’s).

I’ve heard everything from gas blocks being fairly straight forward all the way to ‘no one would use them on a pistol or carbine meant for defense’, but now we’re getting into hearsay. The short answer is I honestly don’t know.
 
OARNGESI said:
Have you thought of switching platforms my tavor is shorter than my 10.5 pistol or many similar to ar setups that don’t use a buffer tubes or even just get a folding hinge it’s a little on the pricy side but you can turn a 16in rifle into roughly the same length as a 7.5 pistol.
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Not interested in another platform. I am finding myself AR stripped lower "poor" so I am kicking the can around on what kind of builds I will be doing.

I am not sure I am really that interested in a AR pistol. I am dipping my toe in the water to see how much I like it.

Thank you guys for the comments so far,
 
BSA1 said:
Is adjustable gas block advisable?
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The only con for an AGB is price.

The advantage is control. All of my personal AR’s have AGB’s for that reason. Pick a recoil impulse you like with reciprocating mass, then tune the gas block to operate reliably - the end result is minimized gas waste, meaning more of the money I spent on powder goes into pushing the bullet, instead of just venting out of the breech.
 
I had a PWS Diablo Mk107 Mod 1 that ran flawlessly with a 7.75" barrel. I never fired it indoors but outdoors the muzzle blast was not objectionable....it was great fun to shoot!
 
I went 7.5” with a purchased Aero upper. Members suggested a flash forwarding device which I purchased, along with an H2 buffer, and I assembled the lower from a stripped Aero.

Mortared the first two casings after forgetting to lube it up beyond a light CLP wipe down and it's been 200 rounds trouble free since. Not an impressive round count, but I’ve had a busy summer between work and vacations.

I too purpose built using the short barrel for JIC situations. Makes for something different to take to the range.
 
10.5", period. Same length and proven record for 55, 62, 75, and 77 grain issued rounds as used in SOCOM and the USCG in the MK18 as well as the older Crane CQBR uppers. Carbine length gasser, so more commonly available parts, as well as more reliability than a 7" pistol gasser which can be more picky with some rounds for functioning. We are only talking about a 3" difference in OAL in a gun that is far from "small" buying you all of this, plus more muzzle velocity and the opportunity to use a longer rail. FWIW, my favorite barrel length for a "shorty" is 11.5".
 
@FL-NC 3" can make a lot of different in a close quarters situation but your comment goes to the heart of my question. 10.5" barrel with along blast deflector (2"+) is getting into SBR territory for me. A SBR in that length makes more sense than leaving it as a handgun. But I don't want to deal with the paperwork and paying $200.00 fee for a SBR.

Essentially a AR-15 makes for a poor handgun.
 
BSA1 said:
Essentially a AR-15 makes for a poor handgun.
Click to expand...
This right here. You can get 30-round mags for most popular semi pistols, in an easier to carry and conceal package. You do lose the rifle cartridge's capabilities, but it is a trade-off for maneuverability. It has it's place, one of many tools, but none are perfect for every situation, which is why I traded mine for a 1911.
 
Tongue firmly in cheek...

How about a 2-inch AR-15. You can see if it loaded cause the bullet is sticking out the end of the barrel. Seems reliable...

 
I believe the KVP is 2.25” OAL which adds ~1.75” after installation or, put in other terms, shorter than a 10.5” with thread protector.

Compared in pics to a 16” barrel middy.


3670C11E-3E81-4E09-9DE9-80B25C188DFC.jpeg


059925A8-9035-499D-AADA-A8CC6F2F9145.jpeg


809A88EA-CB91-448F-9287-15964EF84F68.jpeg
 
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