I am working on a new AR upper and am wanting to build it in a modified A2 configuration.  "What do you mean modified?" you say? well, I want to get an A2 upper with the built in carry handle and rear sight, do a 16" barrel with A2 flash hider and an A2 gas block/front sight, (here comes the modified part) and do it in 300black out with a Magpul MOE SL hand-guard.

Turns out in 300blk, there are not many options I can find for a barrel in the configuration I need.  I do not have the tools to pin a gas block so I was thinking I would just get a barrel assembly with it already attached.  I know I could have a gunsmith do it but I would rather just get one pre assembled for convenience and time.  I also have seen the clamp on A2 gas blocks but that just doesn't make sense to me since you need to align the front sight properly and make sure it stays.  

I know the 300blk is not the most accurate round but I am still looking for something that is around 1.5-2 MOA at 100 yards with premium ammo.  I have seen plenty of sub MOA 300blk rifles, some even with SBR length barrels, so I don't think 1.5 MOA is asking very much.  I am not planning to shoot past 100 yards so accuracy out to 200++ yards is not a concern.  I plan to put a 1-8x24 FFP scope on it or possibly a magnified red dot, like a prism sight or something.

The best choice I have found so far is from CMMG.  They basically have exactly what I am looking for....  https://www.cmmginc.com/shop/barrel-assembly-16-1-mr-4140cm-sbn-300-blk/  ... My question is,  how accurate are CMMG barrels?  More specifically the one in the above link.  I figure if their other barrels are accurate this one is likely to be around the same quality.  Thanks for any future input. Please, only comment if you have experience with CMMG barrels.  I have already searched online and most CMMG reviews are positive but I was hoping to get some feedback from ARFcom.

Stay cool

I've heard mention that some guys are getting MOA to sub MOA accuracy out of CMMG barrels in 300 BLK.

I'm building my first 300 (8" CMMG bbl) as soon as the stamp comes back but that won't be for a few months so I have no first hand with the platform right now.

I really want to build mine with a 10" barrel but I don't live in a free state. (CA)

Not Cool

Go with a PISTOL gas barrel, and get a setscrew gas block.  Then get an "A2-type" clamp on FSB.  The gas block will hide under your handguards and the clamp on FSB will give you the look (and sight radius) you want.

You want pistol gas because 300 Blackout works best (no matter the barrel length) with pistol gas.  It is essentially a hot magnum pistol cartridge, after all.  (No kidding!)