Diamondback Firearms 5.56 AR-15 Barrel - Mid-Length - Nitride - 16"

Manufactured by Diamondback Firearms
SKU: 556M16M50B8
MPN: 556M16M50B8
Manufactured by Diamondback Firearms
78 Reviews

In Stock

Due to the overwhelming response to our Black Friday and Cyber Monday sales, we are working hard to catch up! New orders of non-FFL items will ship within 2 business days (M-F), and FFL orders will ship within 8 business days if transfer details are provided.

For individual Officer, First Responder, and Military pricing please make sure you are logged in. for details



This 16" barrel is manufactured in-house using state-of-the-art CNC machines and is thoroughly inspected at multiple stages of the build process to ensure quality. Precision machined from heavy duty 4150 Chrome Moly Vanadium Steel, this barrel features a 6 groove button rifled bore to ensure consistent accuracy, with a 1:8 twist rate optimal for a variety of bullet weights. The mid-length gas system is designed for reliable and smooth cycling.

This barrel is threaded 1/2x28 and features an 11 degree target crown. To provide an added layer of protection, the barrel is finished with a durable salt bath Nitride coating. Designed by Diamondback Barrels Co., this barrel also features M4 feed ramps and is compatible with a wide range of AR-15 parts. The medium contour/profile of the barrel provides a good balance of weight and heat dissipation.


  • 16" barrel chambered in 5.56 NATO
  • Machined from 4150 CMV steel
  • Salt Bath Nitride finish for added durability
  • Mid-length gas system for reliable cycling
  • 1:8 twist rate for optimal bullet stability
  • 6 groove button rifled bore for consistent accuracy
  • 11 degree target crown for enhanced precision
  • Threaded 1/2x28
See More


Barrel CoatingSalt Bath Nitride
Barrel ContourMedium
Barrel Length16
Barrel Material4150 Chrome Moly Steel
BrandDiamondback Firearms
Caliber Gauge5.56 NATO
Feed RampsM4
Gas Seat Diameter.750
Gas System LengthMid-Length
Thread Pattern1/2 X 28
Twist Rate1:8
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

78 reviews


Gas port drilled out of alignment

by -

Bought on sale. The description sounded good. Got it home and dimpled the barrel for a gas block. They are not dimpled.
While putting everything together, noticed that the gas port was drilled out of alignment with the index pin. So now I have a canted gas block under the handguard. I could deal with a slight cant, but this one is pretty bad. Well, now I just need to shoot it. If it doesn't shoot well, it is coming off. So I will update this review after I shoot it. I would not buy another Diamondback barrel.

Nice finish, great fit

by -

Got this as part of my budget AR build. It fits great into my Bear Creek upper. The finish is also nice with no marks.

No gas block set screw dimples

by -

Beware that the barrel is not dimpled for the gas block set screws. That is the only reason Im giving 4 stars instead of 5. Will have to buy a jig to drill barrel, but its no big deal to me. Other than that Primary Arms is awesome as always with fast delivery and great customer service and for that I am a customer for life

Would not recommend

by -

Barrel does not have dimples for gas block and chamber has deep grooves in it grabbing the brass upon pressure expansion. Would not let BCG Ejector grab brass and had to be manually forced out of chamber with a cleaning rod through the muzzle. Eventually, after using a chamber brush and chamber mop and heating the barrel up through single round shots it polished the groove out of the chamber. Have not malfunctioned since but a severe headache compared to other reputable manufacturers on the market where you can seat the barrel and move on. You get what you pay for on this one.

Crooked Gas Ports

by -

These barrels have crooked gas ports.

Excellent...especially for the price.

by -

True it does not have a dimple for the gas block, but for the price and accuracy, I can't complain. I buldt it for a truck gun and put open flip up sights on it. I sighted it in at 100 yrs with 2 shots then adjust to zero with 4 two shot groups. In all 4 groups the 2 shots were with in .5"-.75" of each other. I know this isn't a true accuracy test, but I am very pleased with the barrel.

Great barrel for the money

by -

Paired this up with a bear creek upper and bcg. Was on zero after just a few shots. Shot 1 moa, 5 shot group, with 55 grain hornady soft points running 26.4 grains of cfe 223. I am very impressed with the accuracy using a mil spec trigger. I have used a couple other Diamondback barrels in the past with the same luck.

No dimples? No problem!

by -

I have built hundreds of Ar15s over the past 30 plus years. This is a great barrel and the lack of dimples for a gas block means nothing on a barrel where the handguard will cover the gas block. I have never had a gas block come loose with this setup. The only thing the dimple really does is help align the block with the gas port.

Visible Burr on Rifling is Disappointing

by -

This barrel falls into the "you get what you pay for" category. I put this in a close range rifle that didnt need sub moa accuracy so I figured this bargain barrel would do.

The fit and finish is decent. There was wiggle in the extension to upper fit but not too much. The gas port and gas journal are properly sized. Muzzle threads are correct.

The bad: Upon first inspection, I could see a burr on the rifling inside the barrel. It was small enough that I decided to install the barrel and shoot the burr out. After firing the rifle the first time the small pieces of excess metal ended up inside my gas system and blocked the flow of gas. The rifle would not fully cycle. I had to disassemble the muzzle device, gas block and tube to blow it all out with an air compressor and do a full cleaning of the BCG to remove the bits of small metal. After all this the rifle functioned properly.

Accuracy has been acceptable with wolf steel.

You get what you pay for

by -

Visible burr on the rifling halfway down the barrel. A brass brush did not remove it. I ended up shooting it out which sent small pieces of metal into my gas system gumming things up. Other then that, its been fine and is in spec.

I dont think Id recommend this barrel to others unless it was for an absolute bargain bin build.