CMMG MK3 Lower and Rock River LR8 upper compatability

[1911whore]

Will they fit together or are these not compatible? If there is an AR10 guru out there, I would love to pick your brain.

[kcheung2]

I'm not an Ar308 guru but my understanding is that Rock River is it's own platform & doesn't play well with anyone else.

[1911whore]

I see that too....So my next question would be what upper will produce half to one MOA accuracy that does play well?

[kcheung2]

Well when you figure it out let me know because I have the same lower, lol. I'm leaning towards an Aeroprecision nitrided 18" or 20" upper.

[1911whore]

Where is randall when you need him

[CaliDoc]

Aero Precision makes uppers, CMMG makes them as well. There are others and you could always build out a custom barreled upper

https://www.cmmginc.com/shop/upper-group-mk3-cbr-308-win/

http://aeroprecisionusa.com/m5e1-308-20in-rifle-ss-complete-upper.html

[berg]

The DPMS SASS upper is incredibly accurate though heavy. CMMG makes an upper specifically for their lower that can shoot to your accuracy requirement. Midway just had the 18" stainless version on sale for $850.

[1911whore]

The DPMS SASS upper is incredibly accurate though heavy. CMMG makes an upper specifically for their lower that can shoot to your accuracy requirement. Midway just had the 18" stainless version on sale for $850.

Unless I am missing the right info, what I read online is the CMMG mk 3 LR-308 upper is about a 1.5 moa rig.

[nate76239]

My brother has the cmmg MK3 lower and it fits a DPMS oracle upper

[Drew Eckhardt]

I see that too....So my next question would be what upper will produce half to one MOA accuracy that does play well?

Rhino guarantees 0.5 MOA on their complete guns.

Fulton guarantees 1 MOA on their complete guns and .223 uppers.

Neither makes guarantees when you pair their .308 upper with a different lower, and upper/lower play can produce vertical stringing (the upper moves when the hammer falls).

Barrel extension to upper fit matters, with the US Army AMU and reputable gunsmiths bedding the two together. The Fulton and Alex Pro (the same part) stripped uppers I examined were tighter on my Fulton sourced M110 AMU profile Krieger barrel.

[lwbyo1]

Your best bet would be to build one. The problem is finding an upper that mates well with your existing lower. The DPMS should fit but will stick out a little around the trigger area. Purely a cosmetic thing.

I'm not sure how an Aero Precision upper will mate up to it. I have an older Fulton Armory lower (rebranded DPMS lower) and there's a small gap (1/8"+) between the bottom of the charging handle and the top of the receiver extension tower. I also had to elongate the takedown pin hole on the upper to get the pin to go in. You'll have to test different uppers on your lower to see what fits and what looks good to you.

Your best bet would be to buy a complete CMMG upper assembly for around $800. Try it out and if it doesn't shoot as well as you like then swap out the barrel with a Bartlein, Krieger, Lilja or JP barrel. With the upper assembly, new barrel, adjustable gas block and muzzle brake, you'll be around $1500 - $1650. Sell the original barrel for $175-$200 and you can recoup some of your money back. If an Aero M5E1 upper does fit well on your lower then you can probably build one for around $1300 - $1450 with one of the aforementioned barrels.

These are just a few ways you could go.