MR6.5G build - looking for input
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Thread: MR6.5G build - looking for input

  1. #1
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    Default MR6.5G build - looking for input

    Hey y’all, I got hooked on 6.5 Grendel DI builds and reloading, and I intend on converting one of my MR556A1s to this caliber.
    Alexander Arms 6.5G DI bolt with gas rings removed should operate in the MR556 bolt carrier, will check fit shortly.
    Just sent funds for 2 HK416 barrel extensions and a spare MR556 gas block for modification.
    Will have a 6.5G SS match barrel blank (Wilson, Shilen, Kreiger) chambered for 6.5G and 416 barrel extension installed, same barrel profile as MR556 including gas port and gas block mounting details. Headspaced to AA bolt. Not settled on barrel length but will maintain .748” past gas block.
    Will have gas block front drilled & tapped for threaded rod to allow gas passage blocking for cycle rate tune in case it is needed. I can open up the barrel gas port if full gas isn’t sufficient. Montrala already successfully made an adjustable MR556 gas block this way.
    6.5G 10 round mags fit MR lower, expectation is 24 round Mags will as well.

    See any show stoppers? Advice? Asked for a quote from Marvin at Nefarious, he sounded positive about making this work when we spoke briefly.
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  2. #2
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    According to "Grumpy", you don't even have to pull the gas rings off the bolt to make it work. He didn't take his gas rings off when he did his test with the DI Noveske (5.56) bolt:
    HK416 /DI parts compatibility

    And you're obviously aware you're going to need to tune this sucker since you're stuck with the HK gas system length. Were it me, I would probably get a Vltor A5 buffer on the back so you can tune there too. In theory, it should all be able to work, but I wonder if you're going to get this sucker tuned down enough that it isn't devouring bolts and trigger disconnectors.

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    Since I use JP Enterprises adjustable gas blocks, I know I can block enough gas to barely move the carrier in a 6.5G rifle length DI system 24 in barrel with the blocking threaded rod. Maybe I should start with an undersized gas port, and I can open it up if I can’t get the carrier to lock back. Good idea on the buffer suggestion, I will read up on that as I’m not familiar with the A5...

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  5. #4
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    And that Grumpy thread was where I saw the successful compatibility testing, I couldn’t remember who checked all that out already. Very helpful!

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    Who are you going to have do your barrel work?

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    I had a brief conversation with Marvin Pitts at Nefarious Arms as I was saying, I asked for a quote. We will see how that goes, he has a reputation here.

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