Expo Arms 5.56 NATO Chrome Lined AR-15 Barrel - SOCOM Profile - Carbine Length - 10.3"

Manufactured by Expo Arms
SKU: XP-B-556-103-SOC-C
MPN: XP-B-556-103-SOC-C
Manufactured by Expo Arms
36 Reviews

Out of Stock

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The Expo Arms AR-15 Barrels are designed to give you a premium barrel at an affordable cost. This AR barrel is made from Mil-Spec 11595E certified 4150 steel and features a chrome lined bore to withstand high temperatures for a long barrel life. This 10.3” model features a SOCOM profile with a carbine gas system and .070” port diameter for reliable function. Additionally, the .750 gas seat diameter is dimpled for securely attaching set screw gas blocks. The 1:7 twist rate is optimal for heavier 62 grain ammunition and the muzzle is threaded 1/2x28 for your favorite 5.56 muzzle device. The entire 5.56 Barrel is Phosphate coated for corrosion resistance and oil absorption. If you are looking for a combat ready barrel that provides exceptional accuracy and reliability, you can’t go wrong with an Expo Arms M4 barrel.

Note: Due to the Crane-Spec gas port size of .070” this barrel was designed to function both unsuppressed and suppressed with 5.56 NATO pressure ammunition. Unsuppressed use with lower pressure .223 Remington ammunition may not yield the best results regarding function.

  • 10.3” Government profile chambered in 5.56 NATO
  • Carbine gas system with .070” port diameter
  • .750” dimpled gas block shelf
  • Made from Mil-Spec 11595E 4150 steel
  • Chrome lined bore with Phosphate outer finish
  • 1:7 twist rate and 1/2x28 muzzle thread
  • M4 feed ramps
Expo Arms offers top-quality MIL-SPEC AR-15 components at rock bottom prices. Made in the U.S.A. and covered by Expo’s Limited Lifetime Warranty against manufacturer defects, material or workmanship problems, and even normal wear and tear.
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Barrel CoatingManganese Phosphate
Barrel ContourSOCOM
Barrel Length10.3
Barrel LiningChrome
Barrel Material4150 Chrome Moly Steel
BrandExpo Arms
Caliber Gauge5.56 NATO
Feed RampsM4
Gas Seat Diameter.750
Gas System LengthCarbine
Thread Pattern1/2 X 28
Twist Rate1:7
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to www.P65Warnings.ca.gov.

Ratings & Reviews

36 reviews


Primary Arms is spot on

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Outstanding Barrel, Zero issues, used 5.56 and 223. I used iron sights only and it was spot on at 25 yards and 50 yards. I can't say enough about this barrel. Build a MK18 clone.

Buy this barrel!

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This is a sleeper barrel.
This barrel is spec'd correctly and install was very snug in 2 separate upper recievers. 10.3" barrel was giving me appx 1.15" moa/100yds with 77gn Match King with Swampfox Arrowhead at benchrest.
Great barrel, I wouldn't hesitate to buy another!

Excellent barrel


Works great with Russian 55 grain ammo.


by -

Impressive for the price point. Thick heavy uniform chrome bore, heavy park, clean concentric threads.

Gas port is slightly smaller than .070 but that’s a 30 second fix. Gun runs great with and without a RC2 Socom.

Dimpled for gas block, shipped in sealed plastic, soaked in milspec heavy storage oil.

Need a 14.5/13.7 heavy profile next

Great product, will buy more.


Very snug fit in my upper. Had to tap in with a plastic mallet. Functions well and accuracy is actually impressive. At 50 yards, Prime 77gr ammo was doing 1/2" 5 shot groups with a 4MOA dot reflex sight. I'd be curious to see what this can do with a magnified optic.

As an aside, not directly attributed to the barrel per se: I'm working on some gas regulation issues and finding the right spring/buffer weight for my different ammo I shoot from 55gr reloads, 223 stuff, NATO 55/62gr loads, and 75/77gr stuff. I may just need to find one cartridge and just do that for reliability.

So Far So Good


At just over a hundred monies, thought I take a chance for a high-end pistol build. It may sound funny to go with a "cheap" barrel on a high end build, but I'm confident it's a good barrel because I know many of the other OEMs who make Expo parts for PA and they're all very reputable. While I'm not suggesting your going to get a DD or FN barrel at this price, the fact is I (like most civilians) don't shoot 1000 rounds a month, or need pinpoint accuracy to 300 yards out of a 10.3 pistol. I just need a good barrel that will feed and shoot reliably with hot defense ammo, isn't over-gassed with or without a suppressor, and has minute-of-torso accuracy at 50 yards. Keep in mind, that also means you need to feed it appropriately with M855 or something similar, because low pressure .223 isn't going to cycle even unsuppressed (at least it wouldn't with the Geissele Super 42 spring and H2). While I haven't shot it a lot, so far this barrel is showing me it can do what I need it to.



I can smack 8" plate all day long with a red dot. Excellent finish and price.

10.3 barrel

by -

Nice barrel Good tight fit in upper haven't shot yet but the other barrels shoot great .

Fantastic barrel and the price is icing on the cake

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Appropriately gased, dimpled (actually at top dead center unlike some higher end ones I have had), awesome profile, chromed lined and fit snugs in my receiver. Checks all the boxex. This is a case of get more than you pay for or maybe I have just been overpaying before. :)

Build your own Mark18 clone!

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Very impressed with the overall quality of the machining and chrome lining. Bore scoped it after running an alcohol patch and the rifling and chrome lining were awesome. Built a Mk18 clone with an adjustable gas block leaving the gas port alone, as is, at .070" and so far so good with 5.56. Will see if it will run ,223. Have not run it suppressed but I can reduce the gas even further if needed. I highly recommend this barrel.
It shoots well and should last longer than me.
So if considering a SOCOM profile with a carbine gas system and .070” port diameter for reliable function, this is a good option at a great price. Caught mine on sale for $80. Thanks PA.