Best SBR AR-15 BBL Length

[ratt_finkel]

I've been thinking about building an SBR AR-15. One with extreme mobility and handling. But won't be a total compromise in accuracy or long range shooting.

I realize it will be diminished compared to anything 16" and longer.

So what's the ideal barrel size? 5" - 10" - 14", etc.

My goals are light weight
Compact
Handling/carrying
Accuracy (man size target @ 200-300 yards)

At what point does the minimal barrel weight aid significantly in accuracy, or vice versa.

Or is the standard 16" barrel already the best middle ground?

(lets please keep this on point to the AR-15 platform)

Thanks!

EDIT: This would be for off the shelf 5.56/.223 loads.

 

[Snowdog]

Interesting topic. I'm interested in the results.
However, 5" ?
An M193 5.56 55gr pill would start out at what, roughly 1900 FPS and 450 Ft/lbs at the muzzle and sharply dropping to 280 FT/lbs at 100 yards? I can't imagine what you'll have at the 200/300 yard mark, but I doubt it could be described as "effective".

This info was gleaned off BBTI and Handloads.com, but I doubt it's too far off.

Personally, I wouldn't even consider anything much under 14" if you're considering those ranges for anything other than punching paper.

 

[strambo]

The range is pretty narrow since below 10.5" can have hit or miss reliability as well as really low velocity and 14.5" is that last common "SBR" length, but it can also be done non-SBR "permed" so that leaves 10.5, 11.5 or 12.5 as the most common realistic choices.

Whether 10.5, 11.5 or 12.5 is just personal preference and whether you want to skew towards the compact side of the equation or the velocity side. Any will be good for torso hits out to 300yds no problem. From the way you phrased the OP, I think a 12.5 would suit you best. It is a great all-around length.

If we had no NFA, I think something in the 12"-14" range would be ideal for an all-around general purpose AR. Shorter for CQB specific, longer for SPR or hunting specific.

 

[Gordon]

I settled on an Noveske Infidel at 13.7 with their Flaming pig pinned on. The Noveske barrel is fast with polygonal rifling and very smoothly polished stainless. It gives a 100 or better FPS than the same ammo in my 3 14.5"s with pinned brakes. Shorter still really limits your non NFA options allthough there are some 5.5" brakes around to make 10.5" guns legal if pinned. I found the velocity of barrels really drops off below 11" or so and as been previously noted you have a .22 bullet going at .30 carb velocities at pretty short range which effects the forensics.

 

[Olympus]

10.5" is what most people consider the minimum barrel length while still being effective.

 

[Jackal]

Anything below a 10.5 and you might as well just use CCI Minimags...

 

[MachIVshooter]

7.5 inchers ( or 8.5") are fun, and they have their place, but most need some kind of back pressure increasing muzzle device like the Noveske KX3 to truly run 100% with all ammo. They are also pretty limited in effective range, as even with 40 and 50 grain loads, their initial velocity is relatively low. I consider my 7.5's effective range to be <150 yards. Also, a lot of suppressors are not intended for and warrantied with use on such short barrels.

10.5-12.5 are pretty ideal for SBR. With a suppressor, you end up having a weapon that is about the length (or a little less) than a 20" gun. They still pay a velocity penalty, but effective range is about double that of the pistol length tubes.

Once you're moving into the 13.7"/14.5" range, IMO, it's not worth going SBR. Just permanently attach a muzzle device and keep it title I, save the $200. Also, IMO, a 14.5" isn't really any handier than a 16", just gives up ~50 FPS. I do have one 14.5 with a permanent muzzle brake, but the goal was a featherweight, which is why I chose a shorter tube (which I turned down to sub-pencil profile), with the 16" length made by pinning a Ti muzzle brake I machined. Rifle is under 5 lbs with optics.

Of course, if you already have an SBR lower, then buy a bunch of shorty uppers just because . I have a 7.5", 10.5" and a 12.5", as well as a 10" .300 Blk.

This is my 12.5" configuration, which I consider to be the best balanced between portability/handiness and utility:

 

[Jenrick]

What kind of ammo are you using, and for what purpose? Ringing steel for the heck of it is, is way different then social purposes.

-Jenrick

 

[gotigers]

Don't go shorter than a typical suppressor warranty: 10.5" long.
+
You want to go as short as you can.
=
10.5"

You'll hear arguments about needing the extra velocity of 11, 12, etc. A 10.5 has enough velocity for 75gr T2 TAP, 77gr MK262, 77gr IMI razorcore to be lethal past 150 yards. Plenty for HD/SD. Loads like Federal Fusion or 50gr TSX will do even better. Bullet manufacturers post their bullet's expansion thresholds. Most good bullets will properly expand around 2000 fps. My 10.5 easily has 2000 fps with every load I've tried out to 150 yards.

A 5.56 shorter than 10" and you will get into serious velocity losses.

Why spend the money on a stamp for a 14.5". Go big or go home. 10.5" is the way to go.

My 10.5 has run flawless with every load I tried and I've tried a lot. Just get a quality barrel. Daniel Defense, FN, etc. They will have properly sized gas ports.

 

[sappyg]

I've put over 500 rounds through one 10.5" upper and close to 100 in another 10.5" on an AR pistol and that's as short as I care to go. Accuracy is fine but I don't shoot them @ 2-300 yards. Fairly certain I could hit a man sized target with them at that distance. My eyesight would be a bigger concern.
If you're worried about ballistics at 300 yards an SBR might not be what you are looking for. For me, a 16" barreled AR covers a lot of bases.

 

[crazysccrmd]

I have a 10.5" 5.56 SBR and that's the shortest I'd go. Even with a suppressor it still has an uncomfortable tone to it when shooting without ear pro. If you're willing to consider other caliber look into building a 6.8SPC. It will be much more effective from a short barrel and ammo costs are comparable to what good quality 5.56 costs (~$12/box) and readily available.

 

[Tirod]

Shooting without ear protection at all is a serious safety of use issue with SBR's. The gas pressure continues to rise for every inch shorter and it's more than just noisy when you get to the 10.5" length.

No professional issued the 10.5" barrel shoots without hearing protection. Most shoot with amplified muffs that have their radio communications piped in.

Barrel length study: http://www.sadefensejournal.com/wp/?p=1093

10.5" was selected in 1966 as the shortest usable length when the XM177 was fielded - and as recognition that soldiers were suffering significant hearing loss using it, a moderator adding to knock down the noise level. It was the first general issue suppressor aside from small unit special operations - and classed a silencer by the ATF to this day.

SBR's are loud and shooting one without ear pro is it's own reward. You will go deaf - sooner than shooting longer barrels. The exit pressure is DOUBLE that of a 20". That is a 100% increase in the gas pressure exhausting from the muzzle.

It's also double the pressure operating the action - which is asking a lot and why those who run them full auto see bolts cracking much sooner than "normal." Nonetheless we are talking tens of thousands of rounds.

Anything shorter and the collective thinking on SBR and pistol forums is that the gun becomes more difficult to tune for reliable operation. Longer has incremental advantages - but the point is to have a short barrel, not one slightly shorter than a typical rifle. That's the point - it's NOT a "rifle" other than it meets the legal definition because it has a stock. It's a PDW - something that isn't intended for longer range use.

What do the current issue SBR's in the service do? They are chosen for close quarters combat, where more firepower than a pistol is needed. Shipboarding operations and infra urban combat - like rescuing hostages from pirates at sea, searching for contraband, working thru buildings, or in highly congested vegetation. The point is having a weapon less than 30" because of narrow passages and doorways. A typical rifle for field use is 36-41" and unwieldy in tight quarters.

There is a lot of interest in SBR's now as the typical AR builder is becoming jaded over the traditional accessories and their market development. Choosing a free float of the month for another 16" build doesn't result in something New! on the range. A 10.5" SBR or pistol, tho, is something else.

A pistol is an option many are chosing - they sacrifice the stock to eliminate the NFA registration and stamp, plus the result if built to less than 26" from buffer to muzzle (not muzzle device) classes it as a "pistol" with all the CCW implications. That's where the 10.5" barrel comes in as it results in being less than 26".

We've had the 10.5" since 1966 and it was of interest then. Now, it's arguably the largest growing segment of the AR market.

 

[ratt_finkel]

This is all been very informative thank you. I did some quick research after I posted to make sure there wasn't a recent and or duplicate thread. It appears the general consensus is 10.5" is the minimum for effective "rifle like" performance. And below that, while probably a blast to shoot (no pun intended). Not really practical for what I have in mind.

Someone asked about what loads I used or social situations? I'm not a load expert, but typically shoot everything from cheap Tula ammo to 50cent a round soft point and hollow points.

Just looking for an agile rifle that has acceptable accuracy to 200-300 yards. And in the AR platform and 5.56/.223 caliber. Based on what I'm hearing, the 10.5" barrel meets that need.

 

[jmorris]

I have a 10.5", with the suppressor it is the same length as a 16" without one.

 

[Ibmikey]

12.5" and DD flash hider added seem just right for my supersonic 300 Blackout fungun.

 

[Zerodefect]

10.5"

12.5"? minus well just build a non-NFA 14.5" AR. 8" and the gun gets finicky. But I'd say 7.5" is best if we allow .300blk into this conversation.

 

[wally]

Don't worry about it. You can go longer or shorter with another upper once you get your stamp.

I started with 7.5" simply because I really liked the way it handled, but quickly added a 10.5" once I got a suppressor.

With a 7.5" stick it through a cracked open door and touch one off into the floor and you've an improvised flash-bang

If muzzle blast bothers you, stick with 16" or longer barrels. The shorter you go the more the blast as the uncorking pressure is higher and its closer to you.

With all the great deals out there on AR parts these days, build up everything you might want as quickly as funds allow!

 

[USAF_Vet]

I've got a 10.5" pistol that I'll be SBR'ing next year. I considered a 7.5" but read that you lose a lot in terms of ballistics, and that 10.5" was the best way to go.

But with a SRB lower, having multiple uppers to fit and play around with seems more viable. I may eventually go with a 7.5" upper, (I already have a free float tube for one) but it's pretty far down on the AR want list. Below the .450 Bushmaster, 9mm, and 20" rifle builds.

 

[MachIVshooter]

12.5"? minus well just build a non-NFA 14.5" AR. 8" and the gun gets finicky. But I'd say 7.5" is best if we allow .300blk into this conversation.

A 14.5" most certainly is NFA unless you do a permanent muzzle device that brings it to 16". There is a big difference in the handling characteristics of a 12.5" versus a 16".

And 7.5" is not ideal for .300 Blk, either. The round was designed for optimal subsonic suppressed performance out of a 10.3" tube. Super sonic loads can benefit from more barrel, but do OK in a 10".

 

[taliv]

my recommendation is a 10.5" barrel from noveske with the switchblock and a shorty suppressor like the delta p designs. imho the suppressor is a requirement due to the hearing safety issues mentioned above.

i would not recommend a cheap barrel or a barrel that has been cut down. i would not expect them to be reliable.

if you don't want a suppressor, then i would recommend an 11.5" bravo co barrel.

 

[wally]

A 14.5" most certainly is NFA unless you do a permanent muzzle device that brings it to 16".

Isn't the BATFE making noises about no longer allowing "permanent" muzzle attachments to count towards barrel length? Maybe it was just a rumor, as I'd have expected to have heard more about it by now.

Supposedly it was in response to those SIG and Ruger barrels with basically mono-core suppressor "guts" permanently attached -- pay the $200 tax and buy the outer tube to complete the suppressor later.

 

[Tirod]

And 7.5" is not ideal for .300 Blk, either. The round was designed for optimal subsonic suppressed performance out of a 10.3" tube.

Not - the .300 x 5.56 was "designed" to allow the AR15 into 3 Gun competition back in the 1980s. It was an expedient wildcat meant to get around the rules that disallowed "poodleshooters" because Real Men only shot .30 cal battle rifles.

It was quickly run off the range at the First Invitational SOF Match at Chapman Range in Columbia, MO back in the early '80s, but it didn't go away. SSK kept developing it and found it had a good application as a niche suppressed round.

AAC lifted the entire cartridge design, changed a few non-critical dimensions, and renamed the .300 Whisper to .300 Blackout. And here we are - shooting it for the most part supersonic by most builders looking for something different in the AR Alternate Cartridge of the Month Club.

It's a good suppressed round, but it was not originally meant for that - it was a supersonic wildcat for 3 Gun, where it never got legs and was largely ignored for the last 30 years until suppressors got interesting and Remington put some ad dollars behind it.

As the OP was building a 5.56 it's also not on topic - but since it was mentioned, then some would suggest that 6.5 Grendel or 6.8 SPC could do better. The issue for a lot of us is the expense - I'm still waiting on cheap gov't surplus 6.8 at 17c a round. Don't think I will ever see it. So I build a AR pistol in 5.56 to feed it.

A 10.5" barrel will carry 1,000 foot pounds of force out to 80m - good for hunting. At 200 its potentially lethal but I wouldn't prefer it over a 16" for long range work. It's not suited for that. I's a close range PDW at 10.5" and stretching that out to 200 is like trying a 20" M16 at 600m. Just because you can doesn't mean you should - or that a good shooter can't, either.

If someone plans to use one - get muffs. They are cheaper than a suppressor, and they "silence" the other weapons around you. Again, that is the professional recommendation. The military uses suppressors for the tactical purpose of not announcing where the shooter is, what is happening, or putting muzzle blast in a team mate's face in close proximity.

For us on a firing line or for HD, the muffs are about ten times cheaper, too. And you aren't registered with the ATF nor do you have to jump thru all the legal hoops.

We've had them available for years but the bad boyz factor of a suppressor is what is really driving sales. it's a trade off - suppressors just jack up the length of the overall firearm and you wind up right back where you started, $1000 poorer.

But - You Bad!

 

[Zerodefect]

Who the heck would NFA a 14.5" when you can perm a muzzle device in literally 5 minutes. And remove it and perm another in 10.

Were not seeing jack between 10" and 7.5" .300blk pistols. Maybe 80fps.

 

[MachIVshooter]

Not - the .300 x 5.56 was "designed" to allow the AR15 into 3 Gun competition back in the 1980s. It was an expedient wildcat meant to get around the rules that disallowed "poodleshooters" because Real Men only shot .30 cal battle rifles.

It was quickly run off the range at the First Invitational SOF Match at Chapman Range in Columbia, MO back in the early '80s, but it didn't go away. SSK kept developing it and found it had a good application as a niche suppressed round.

AAC lifted the entire cartridge design, changed a few non-critical dimensions, and renamed the .300 Whisper to .300 Blackout. And here we are - shooting it for the most part supersonic by most builders looking for something different in the AR Alternate Cartridge of the Month Club.

It's a good suppressed round, but it was not originally meant for that - it was a supersonic wildcat for 3 Gun, where it never got legs and was largely ignored for the last 30 years until suppressors got interesting and Remington put some ad dollars behind it.

According to the information I have, J.D. Jones, while working for SSK Industries, specifically designed the round to run heavy-for-caliber high B.C. bullets at subsonic velocities for suppressed use. Hence calling it the .300 Whisper, as in quiet.

The reason for the nomenclature is also easily confirmed here, at the source: http://sskindustries.com/300-whisper/

A “Whisper®” cartridge must be capable of sub-sonic extreme accuracy with very heavy bullets for its caliber

 

[ratt_finkel]

I guess I must be the odd duck. I never shoot bare. Always with eyes and ears on. Whether indoors or out. No immediate or planned intention to suppress this SBR.

I have a bushy, early 2000's carbine now. 14.5"plus pinned muzzle brake.

I'm a smaller guy. 5'6" 150lbs. Very muscular since I do weight training. And have no problem wielding my Soccom II around fully loaded with optics and 30 rd mag. But I just think it would be nice to have a smaller AR. Obviously, a big part of the mobility is weight. And a big part of the weight is in the barrel. Hence the thread.

In time, I'll have an array of different sizes. But this is not my main hobby. So for now, a small AR is on my list. Then a big one. Then some of the odd calibers, etc down the line.