Home CMMG CMMG MK3 Short Barrel 308 AR 10 Pistol

CMMG MK3 Short Barrel 308 AR 10 Pistol

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Often when someone says 308 Winchester, they think of a precision rifle vs battle rifle. Well in today’s video we are going to be talking about the exact opposite, a lightweight 308 AR 10 Pistol. The impetus of this video is to start a series working toward the ultimate Short Barrel 308 but we are going to start out slow and do a review of the base gun before we get crazy. To that end we are starting with a Cmmg mk3 12.5 308 ar pistol. Ar rifles in 308 caliber tend to be less popular because of their expense, but also the AR 15 compared to the ar 10 is much lighter. However to step up to the heavier caliber this is certainly required

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Chapters
00:00 WTF? Short 308?
01:56 Overview
04:53 Chrono
05:47 Accuracy
09:38 Problem?
15:05 What’s Next?

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48 COMMENTS

  1. It looks like the same issue as one of the SA80 A1's problems. On the SA80 the clocking handle acts as the deflector, the A1 had a round clocking handle which caused the casing to bounce back into ejection port, the cockingg handle was redesigned on the A2 to deflect the casings out to the side. I expect if the shape oof the deflector was altered it would solve the stoppage issue for you.

  2. There's a company called slashs heavy buffers. The guys name is clint I believe but don't quote me on that. He makes buffers for the 308, 5.56 carbine and car buffers. Even an 8.5oz buffer. You can include the wolf xp spring in the package for like 10 more dollars. I run his 7.5oz in my lmt. That will slow the bolt down enough to allow the pressure to drop before extraction, and drop the bolt velocity enough to give the case time to eject completely. Cmmg is probably going to make a bolt weight tuning kit like they do for the radial delayed banshees. Pof accomplishes this by using a rifle length spring. You are way more knowledgeable than me but I hope this helps, awesome video

  3. About time i see a good review on an AR10 pistol lol i built one off a stag upper/lower mine don’t jam lol ballistic advantage 12.5 barrel SI adjustable gas block kaw vally 5.6oz buffer 🤘🏼

  4. I put a BCM intermediate buffer tube, so I could then use standard size buffers in the .308 as opposed to a shorty. This allows greater buffer weights.. but, that is not all.. I also used a Red Heavy power spring and mine sings now. Mine was ejecting about as yours in now before these changes and now its 3 oclock with an H2.

  5. Your issue is stemming from the short dwell time created by closeness of the gas block to the muzzle. .308 ARs tend to be overgassed, but most likely CMMG opened up the port to allow it to cycle. The short dwell time is difficult to address because the operational "window" of reliable cycling is small. The overgassing is a bandaid to get it to run. The suppressor and the AGB should fix the problem for the most part. The suppressor will give you more dwell time, and the AGB will allow you to tune the window.

  6. Armaspec. 308 Stealth Recoil Spring! I love those captured buffer systems. It really smooths out the recoil impulse. Aero Precision recently released their own Adjustable Gas Block. I run one a 5.56 suppressed upper and seems to work well. My own AR10 .308 (16") runs a mid-length gas system, superlative arms adjustable gas block and an Armaspec SRS. Great shooter without any performance issues thus far. It's become my go to for defensive use outside of my residential property.

  7. I just got an aero m5 receiver and was 50/50 between a 20in barrel rifle and something shorter like this…any chance of getting the overall length? AR pistols are a no go in my state, but if its over 26in, non-nfa "other" firearms are good to go. Thanks

  8. Also be sure check the specs on the bolt travel. If it is traveling too far, you’ll see similar case throat denting, in my experience. If you’re seeing marking on the back side of the ejection port, this makes it even more likely. Turning down the gas can slow the bolt down enough for the case to clear the port properly, but it might only be masking a different issue that will only be complicated with suppression.

    Overall, I dig the idea of a shorty 308. Great video, and thanks for sharing.

  9. I have heard good things about the Superlative Arms adjustable gas blocks for suppressed use. Unfortunately I can't speak from experience as my cans are still under quarantine.

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