OE-SPEC- 300 Blackout 4.75" Micro gas, AR15 Barrel- Nitride

(12 reviews)
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300 Blackout 4.75" AR15 Barrel- Nitride

• Chamber- 300 Blackout 

• Length- 4.75

• Gas system- Micro Length

• Gas Block Size- .750

• Threads- 5/8-24

• Finish- Melonite 

• Twist- 1:7 5R

• Material- 41V50 Chrome Moly Vanadium

• Extension- M4 Ramps 

• Barrel dimpled for gas block set screw

• Marked for Caliber and Twist

• Weight- 10.56 OZ

• Fully Made In House From KAK Industry Produced Blanks

As a high volume contract manufacturer for the firearms industry, KAK is able to leverage its machining capacity to bring the same quality parts that we provide to some of the biggest names in the industry, straight to the retail customer.  We manufacture our barrels from the raw material all the way to the complete product, all under our own roof.  Our barrels are fully inspected through the entire process, including air-gauging the bores, physical measurements of the threads and outer diameters, and 100% gauging of the headspace tolerance.  Our OE-Spec line provides you with the quality you demand and the value you desire.


300 Blackout


  • 5
    4.75" 300 blackout barrel

    Posted by Chris on October 21, 2023

    I have alway want a sig rattler but its way out of my budget. I honestly thought that this super short 4.75" 300 blk barrel would be a giant waste of time. I assumed it wouldn't be reliable, I assumed it wouldn't be little and I couldn't be happier to have been so wrong! It has become on my my favorite pistol builds, it has ran flawlessly from day one. With no fancy parts and goes everywhere with me in a low key sling bag. Thank you kak industries you guy rock !!!!

  • 5
    4.75 300 BLK BARREL

    Posted by EPHRAM STRINGER on August 8, 2023


  • 5
    Stellar quality as always

    Posted by Shortdog on April 25, 2023

    These guys have not failed me yet. Always lightning quick delivery of quality one of a kind products made in house. These short barrels of all calibers are unmatchable and they grant the outside the box ingenuity all the other companies and manufacturers ignored. The look of the craftsmanship is amazing with outstanding consistency amongst barrels of the same caliber. I'm gonna buy again and recommend all my responsible gun owner friends. Can't go wrong with these guys on anything they produce not just the barrels.

  • 5
    Nice Fit & Finish

    Posted by @paperordnance on January 3, 2022

    So far so good. Wanted to build super short barrel blackout SBR with one of my lower receivers. Barrel and gas block fit flawlessly. No rounds through it yet but no plans on going any further than 60 - 100 yards or so with this. Great value and fast shipping!

  • 5

    Posted by Tony on May 2, 2020

    real nice barrel and great quality!

  • 5
    Great Value

    Posted by Benjamin on April 17, 2020

    Shoot great, everything went smooth.

  • 5

    Posted by Jason on April 7, 2020

    First time KAK buyer here. I live in FL and the package arrived quickly. Funny.....I ordered a part from Orlando and the barrel from California arrived first! The barrel, gas block, and tube installed without a problem. Some have stated issues with the gas tube, but my set up didn't have that problem. I haven't had an opportunity to test fire this yet....darn COVID! I will test the set up this coming weekend. Overall this is a great barrel value for what you get. I'll more than likely buy again from KAK from this positive experience.

  • 5
    Great Product and Shipped Quick

    Posted by Noah on March 30, 2020

    Barrel is great and I purchased it with the KAK short gas tube, which this setup won't work without. I did run into an issue, I tried to use a longer barrel nut and the gas tube is so short it hit the barrel nut and wouldn't seat. So I had to order a shorter barrel nut for this setup. Just FYI.

  • 5
    I was skeptical but boy was I wrong. Ran like a champ!

    Posted by Brian on January 11, 2020

    When I hatched the idea to build a super short PDW style AR I was skeptical that the physics would allow for as tiny a build I was looking for. There were mixed feelings online about the micro style in general. But given the objective, the AR platform seemed to be the most workable solution... if it worked. My concern was lack of dwell time resulting in lack of direct impingement pressure and excessive post muzzle exit burn. I was confident I could at least make it work but I was also worried about the downrange performance. At first I was thinking 5.56x45 but when thinking it through realized I wanted to put some mass in the projectile and with a more favorable burn profile I opted for 300 AAC BO. That's when I found this barrel. This puts the overall length of my pistol at 20.6" and an overall weight with empty mag of 5 lbs 5.6 oz with red dot, buis, and Streamlight TLR-1 unloaded. With the halves separated the whole thing fits in a 5.11 4-Banger go bag. I have several Value Line barrels in builds and this one looks to be of the same quality. I was shocked at how big the gas port is drilled but was happy to see it since I wanted to make sure the gun cycled well. I opted for an adjustable block so I could reduce the reciprocating force of the bolt as much as possible, thus ideally combined with the huge gas port. After a quick assembly I took it out to the range with two different loads: (1) 168gr OTM over H110 and (2) 110 gr V-Max over Alliant 2400 to check the difference between the two outside profiles I wanted. First worked with the 168s and was pleased to print a 2" group at 50 yds. Then shot the 110s and it was basically like setting off a flamethrower. Quit those after 3 rounds. I'm going to be moving it back to 150 gr projectiles with both powders and see what the difference is again with the same bullet. But in both cases recoil was minimal and functionals were perfect. Overall I'm ecstatic. Both types of loads worked perfectly with no cycling issues and lockback of the bolt everytime. I just need to get the load fine-tuned and chrono'd and I'll have a PDW in a briefcase sized setup that's both reliable and adequately accurate. Also FYI, my PMAG did not work. Lancer did well, but most of the shooting was done with ETS.