A Visual Library of AR-15 Barrel Profiles


A1 Profile

The is the profile found on the Colt M16A1.  It’s thin underneath the handguards, thin at the gas block journal and thin past the front sight base.  The diameter of the gas block journal is 0.625".  The A1 profile is affectionately referred to as a “pencil” barrel (‘cause John Wick once killed three men in a bar with one.)

Colt 20” A1 profile . . .




barrel stamp . . .






A 16” rendition of the A1 profile barrel is found on the Colt 6520 and 6720.

Colt 16” 6520/6720 barrel . . .




barrel stamp . . .






Government Profile

This is the profile of the barrels found on the M16A2/A3/A4.  It’s basically the same profile underneath the handguards as the A1 profile, with additional material added from the gas block journal forward.  The diameter of the gas block journal is 0.750".

Colt 20” government profile . . .




barrel stamp . . .





An M203 grenade launcher can be attached to the 20” government profile barrel without any modifications to the barrel.
Government profile barrels that are significantly shorter than the 20” barrel required the addition of “cutouts” on the barrel forward of the front sight base to be able to attach an M203 grenade launcher.   Examples of government profile barrels with the M203 cutouts  include the Colt 14.5” M4 barrel and the Colt 16” 6920 barrel.

Colt 14.5” government profile . . .





barrel stamp . . .






Colt 16” government profile . . .




barrel stamp . . .






Medium Contour Profile

Medium contour profiles were designed to provide a higher level of precision and heat tolerance than government profile profiles, without adding as much weight as a heavy barrel profile.


Noveske medium contour 16” RECON barrel . . .






Colt medium contour 14.5” M4A1 SOCOM barrel . . .




barrel stamp . . .






Colt medium contour 11.5” FBI HRT barrel . . .




barrel stamp . . .







Heavy Barrel Profile

Heavy barrel (HBAR) profiles weigh more than medium contour barrels of the same length with most of that extra weight usually being distributed from in front of the barrel extension to the gas block journal.

Colt 20” HBAR . . .




barrel stamp . . .





Colt 16” HBAR . . .




barrel stamp . . .






Bull Barrel Profile


Topping the scales for AR-15 barrels is the bull barrel profile.  These barrels have just about as large a diameter as you can have on an AR-15 barrel while still being able to pass a standard barrel nut over the barrel.  These barrels are a joy to shoot off a bi-pod or bench.  However, carrying them around in the field; not so much.


Lothar Walther 20” bull barrel . . .






Krieger 24” bull barrel . . .






Enhanced Profiles

Over the last several years we’ve seen the emergence of barrels produced by manufacturers with specific objectives of balancing weight distribution and handling characteristics while maintaining accuracy on par with barrels with heavier profiles.  A prime example of this profile is Bravo Company's ELW (enhanced light weight) barrel.

Well over a decade ago, the late John Noveske was the impetus for bringing modern AR-15 barrel profiles to the civilian market.  His 16" CHF N4 barrel profile has the same weight as a government profile barrel of the same length, but it has a more intelligently designed contour that places more of the weight of the barrel from the chamber to the gas block journal and does away with the M203 cut-outs.

Bravo Company 14.5” ELW profile . . .






Noveske 16” N4 profile




TRIARC Track 2.0 16" barrel . . .






Criterion 16" CORE barrel . . .











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A useful quick reference, thanks for posting.

Solid post.

Wonderful post  and solid work as always "M".

Neat! Thanks!

Thanks for sharing.

I may be confused, but I don’t see the utility of a “heavy” profile for a 16” barrel.  Open to being enlightened.

More rounds through before significant zero shift, less wear on the grooves due to lower heat.  Marines are running 16" bbl on their Squad Automatic Rifle, had better be heavy.

Accuracy and heat dispersion .

Nice, thanks for the info

Canada originally wanted to use HBAR barrels in their C7 rifles, but due to the requirement that they be made in Canada, Colt at the time wouldn't allow HBAR barrels to be made in Canada, so Canada went with government profile barrels.

For starters . . .







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<This. My 16" Colt 1/9 H-Bar carbine gassed upper was a sub MOA rifle with match grade bullets right out of the gate. Excellent accuracy from a factory chrome lined barrel.

My suggestion to everyone buying or building an upper is to consider a mid-weight, SPR, Hoplite or similar profile for accuracy work. 1/7 or 1/8 doesn't matter, barrel quality does.

Lightweight barrels can shoot very well, but the mid-weight variety is the best of both worlds.

As someone who lives in MD and is only allowed to buy heavy barrels for new rifles, there is no consistency regarding this at all across the industry. As was mentioned in the other thread, Colt and the military call the Socom barrel a heavy barrel. Faxon has heavy barrels that you call medium. FN makes a heavy barrel you would call medium. When your definition conflicts with Colt and FN, two of the most respected barrel manufactures in the industry, you have to take a step back and admit there is no consensus.

EDIT: Not sure if Colt actually makes barrels, but everyone knows FN makes their own barrels.

There's no consistency b/c bbl manufacturers want to sell bbls to Maryland AR owners - hence anything can be labeled a heavy bbl.  When I get my website going, there will be a normal bbl section, and a Maryland Heavy Bbl section.  All the bbls will be in both sections.

The US military doesn’t call the Socom barrel a heavy barrel so they can sell to MD.

Be careful, pretty sure MSP says it has to be marked or advertised as heavy by the manufacturer, and I’m assuming you aren’t making them.

Ah, fair enuf.  I do know a custom bbl manufacturer, however.  

Very nice. Thanks.

IIRC, this is correct.  

That's a major part of the equation that some people don't seem to grasp.







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That's the idea!

Glad to have you back, Molon.

I finally understand what a "government profile" is and why it's different on the 20" vs 16" guns. Thank you.

You should include the BCM enhanced medium weight fluted barrel in the last section. Really neat profile.

Great information, as usual, Molon. Thanks.

Excellent. Molon, site resources just went up.

I've gone from heavy, to medium, to lightweight.

The nice thing about lightweight is that while they heat up quickly, they also cool quickly.

If you're shooting fancy 30rd rapid fire groups, heavy is nice to have.

Medium is kind of an awkward in between.

Former MD resident - this is correct. MD doesn't care what the retailer/distributor calls it, they get by what the mfg labels and markets it as. Ruger, for instance, makes an MD-compliant AR556 for that express purpose. Sensible? Of course not. But thems the rules.

Great writeup and reference as always Molon.

The vertical "flats" cut into the Colt medium contour M4A1 SOCOM barrel, aft of the gas block journal, are also to accommodate the M203 grenade launcher.

"Out of stock."

Always appreciate the precision of your content & the dedicated to the thoughtful posts.

Now if all the “Socom Hbar” guys out there would read this post

De nada.

good stuff thanks

I like that Hansen profile from ballistic advantage.

What about the "SPR" contour?
Is it based off anything or is it just a invention of the aftermarket?
I have that profile on my 16 inch mid gas carbine (also fluted) and really like it. It adds a little meat to the barrel without adding too much weight. I call it a "happy medium" between a full heavy barrel and the lightweight barrels.
It has a standard .750 gas block and diameter forward of it, while being .850 from the GB back, but tapers up to .950 at the barrel nut.

There is no commercial industry standard for an SPR barrel, but Noveske's 18" SPR barrel is a medium contour barrel.






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Ok, I was not sure. I just see it mentioned semi regularly on barrel listings, but did not see it here.
Just wasn't sure if it was once a factory contour, or a aftermarket invention.

some spr history

Love your posts Molon.

Muchas gracias!  


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I try to read just about every post @Molon makes.   I have learned a good amount of things that i did not know from reading his very informative posts.   Thank you Molon.

As another MD resident, from what I have been able to find out about the Heavy Barrel profile, the state police don't really have a definition either, but they seem to take a 0.750" gas block seat diameter as the standard for a heavy barrel.

I would think that someone who turned out a bbl labeled as Maryland Heavy that everyone else would call a pencil would make a mint.  Throw a .750" gas block seat on it, or larger.

Well done

Muchas gracias!

Another barrel with a modern approach to the profile.

Criterion 16" CORE barrel . . .




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How would one classify the 16" Lilja M4 Navy profile per NSWC Crane specs?  Medium contour?

The drawing states that it weighs 2.25 pounds.  That would place it in HBAR territory.




For comparison . . .

Colt 16" HBAR barrel (6721):  2 pounds, 3.4 ounces.




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Thank you, sir.  Great thread!

Very nice

Big thanks for all your effort to put together this post.  
Prime example of signal over noise.

De nada.

LOL.