Home CMMG CMMG 5.7 Conversion Upper

CMMG 5.7 Conversion Upper

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This 5” upper turns your standard AR-15 into an awesome PDW! It’s so light and small.

Check out CMMG’s YouTube channel:

Here’s some info/links on the product.

– 40rds of 5.7x28mm in a CMMG propriety mag
– Can be purchased as a complete firearm Mk57 lower/upper and Mk4 lower/5.7 upper
– Can purchase BCG/Barrel separately
– Complete uppers offered at 5”, 8” and 16”
– Patented Radial Delayed Blowback
– Offered as a single 40rd mag, 3 pack of 40rd mags and a 10rd mag for restricted states.

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48 COMMENTS

  6. A 5" barrel and 4" handguard is just absurdly short IMO. I wear size 3XL gloves and I couldn't even get a hold on a handguard that small. Would have to hold the magwell so I don't potentially shoot my fingers off. Even for people with normal sized hands, that handguard/barrel is too short. I know that have an 8" one, thats much more practical IMO.

  9. So I'm not as knowledgeable on these conversions, so if I am understanding this correctly, If I have a standard 5.56 lower, I can add this 5.7×28 upper conversion to it and shoot my 5.7 with those 5.7 mags and use a 5.56 suppressor on it (with tax stamp). Also, I can still put my 5.56 upper back on and fire 5.56 with the 5.56 suppressor too? Do I need to change the buffer when you swap out between calibers? This sounds like a win-win. Sorry if this is all obvious. I just have a few handguns and no AR styled rifles, just cheap soviet surplus stuff so far. Thanks,

  17. I’m so glad I saw this video. The full-auto action just made me a buyer. I was skeptical if it would work with my Echo 2 trigger. This upper with a mvb micro buffer will make this a great backpack/car gun.

  19. Sorry, I would rather have an AR57 if I want to shoot 5.7. I hope someone acquires it. 50 round mags are the best mags. Now with pistol braces and the AR57 pistol upper, I think it's time has come and no one is producing it.

    I wondered if shooting the AR57 would be hearing safe as it ejects down? It is full ambi. Did I say 50 round mags?

  23. Sir, thanks for your time putting the video together.

    Recently been looking into the gen 2 echo trigger and wondering if the included BCG would function. Would love to hear your thoughts seeing as you were firing “full auto”. Thanks!

  29. Ordered an 11 inch upper with one mag, and a 3 pack of 40 round mags around 2 weeks ago. Sight says they are shipping mid February. Going to do a pistol build on a PSA lower with a SBA3 , I have an extra Larue MBT S1 trigger I am dropping in. Wish I had a select fire lower. That is extremely nice.

  32. My 9mm ar is this short, actually a little shorter, but yea I am sure that it is heavier. However, it is subsonic most of the time with 115 grain, and all thentime with 147 grain. Do yo think the 5.7 is more quiet than subsonic 9mm?

  45. Okay I thought watching & having a
    Guinness would be great with this my first comment then realize your camera man sounds like it could be your wife I think I love her for loving you awesome🍻💘👍

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