The M4 Barrel Profile And You

Recently, I’ve been hearing a lot of people say “You know what the AR-15 market needs right now? More M4 profile barrels.”

Actually, no, I haven’t heard people say that.

And yet, it seems that every new carbine length upper or rifle in the last year or so has the M203 cutout in the barrel. Even the Bushmaster ACR, which cannot possibly mount an M203, sports the cutout for said purpose.

16" Sabre Defense M4 profile barrel.

So why are companies offering products that no one is really asking for? I do see many people clamoring for lightweight barrels and midlength gas systems. Of course, the entire AR market isn’t on the internet. But Joe Gunowner, unless he wants something that kinda looks like the military M4, might choose something else if M4 type weapons didn’t dominate the racks at every gun store in the country.

I’m relieved to see that Spike’s will be offering lightweight versions of their LE upper, and they’ve already sold plenty of midlength LEs.

Bravo Company has come out with the 16″ lightweight midlength and the 14.5″ midlength uppers.

Daniel Defense is introducing, or has introduced, 16″ and 14.5″ midlengths.

But it seems that, when carbine gas systems are being discussed, the M4 profile reigns supreme.

What advantages does it offer? Well, for the hundreds of thousands of civilian M203 owners out there – oh, wait a second. No, we don’t need the cutout in the barrel for the M203 grenade launcher.

The cutout does provide a visual breakup for the barrels of 16″ rifles, as opposed to the 14.5″ versions used by the military.  It doesn’t seem as long, at least to some.

However, we’d all be much better served from a functional standpoint if the extra steel in front of the FSB was moved behind it. The barrel will generally get hotter under the handguards, so a barrel that’s thicker in the hottest portion will outlast a barrel that’s thin at the hottest portion under sustained full auto fire.

Don’t care about full auto, or even rapid semi auto, shooting? How about balance? With the weight moved under the handguards, the rifle won’t feel as “tipsy” – it’ll feel a little more stable with the weight concentrated close to the center of gravity.

Although taper profiles, such as the Noveske N4 Light, are a more complicated machining task, it would be fairly simple to make the area under the carbine handguards just slightly thicker, while at the same time making the barrel past the FSB .625″ or so.

Of course, we’d have to break the institutional love affair with the M4 profile barrel first.

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6 Comments

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6 responses to “The M4 Barrel Profile And You

  1. Bruce

    I have been shooting AR’s for 35 years. I have followed the “next greatest thing” process in my builds but have only 2 with M4 barrels. One is a SOCOM heavy M4 with a pinned Vortex G6 and the other is an Adams Arms M4 profile barrel (from Spikes $175.00) that is made from stainless steel with a 1:8 twist. This AA M4 is also nitrocarborized (please excuse this spelling) and is the barrel that I am using for a basic build for my son. I generally do not like the M4 profile or the Government profile because these barrels are taken down to .625 for the M203 cut out or under the hand guards or both. I am not a machinist but my thought process tells me that these are the weakest parts of an otherwise .750 barrel.

    I really prefer the mid-length gas system and any future builds will be with the mid-length gas system.

    For my wife’s build I had a Bushmaster 1:7 twist 16″ heavy barrel turned down to .625 for almost the entire length back to the last 4 or 5 inches before the barrel extension. On a Cav Arms Mark 2 lower this makes for a very light weight weapon but still has the 1:7 twist rate. This combo was unavailable when I built this one.

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  4. Kaan

    I’ve had a bug for the last couple of weeks about building a light weight AR. I’ve looked high and low for a “light weight” “.625” “pencil” middy barrel. They are the unicorn that doesn’t truly exist. There is a lot of talk about barrels hitting the market in the next 2-4 weeks, but nothing has been delivered to date.
    I completely agree for the lack of “need” for the M4 barrel. Those companies that make military contract barrels, it’s just easier for them to produce these barrels. But do they really need to push that to the civilian market, by all the companies? Maybe it’s not cost effective enough to “retool” or reprogram the machines?
    Most shooters won’t need anything larger than a “light weight” barrel. The combination of off the shelf ammo, shooter skill, effective ranges of the 5.56, etc, really don’t validate the production of 14.5 bull barrels, heavy barrels, M4 barrels, etc. The lighter your rifle, the more you can shoot it, the farther you can hump it, and the easier it is to move around in competition.
    There is room for Hbar, bulls, and other barrels. But in the 14.5-16inch arena, it’s not needed and it’s over produced by the industry. If one company built, in mass and stocked, light weight full rifles… the market would change, the market would want a lighter rifle!

  5. Stoneboat

    As I machinist I can attest to the fact there is nothing easier about producing an M4 barrel. True MILSPEC are made from the hardest steels to machine – 4150 and CMV. The easiest barrel to make is a straight walled heavy barrel simply because it requires less machining. No tapers or complex radius cuts to make. Cheap fat barrels are cranked out by the millions for shooters that wouldn’t know the difference, shooters that don’t carry their guns any further than the gunsafe/ trunk / shooting bench and back again. The gun “feels” light enough when you only carry it 100 feet at a time. Carry it all day long and it’s a whole different story.
    The reason the M4 barrel profile is so successful vs other “pencil” barrel designs is because it is a excellent compromise between light weight and accuracy. The barrel harmonics of the m4 profile are superior to ultra lights in many ways – to make a long story short, the muzzle end thickness helps tame barrel whip, increases shot to shot consistency and acts much the same as a barrel weight would on an Olympic style target rifle. It’s light under the hand guard because it most cases it doesn’t actually need to be thick there – this in turn significantly reduces weight. You guys are making more out of the M203 cut than bears mentioning – it’s the rest of the barrel design that does it for me, and tens of thousands of others. Just ask any GI that’s carried a 20″ M16 vs an 14.5″ M4 which one they like better.

    • Andrew (Vuurwapen Admin)

      Actually, the barrel needs weight under the handguard more than it does out front. When M4 barrels burst, they burst under the handguards. Comparing an M16 to an M4 doesn’t make a whole lot of sense, of course they’re going to want the lighter one – that doesn’t mean that the illogical barrel profile is somehow a better design than a barrel of the same weight that tapers from rear to front.

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