What are your thoughts on the new 6ARC

[alamo5000]

So I am changing directions on my 6 ARC project. Instead of a 12.5 mini recce spare companion upper for my 5.56 11.5 SBR (stamp is marked 5.56 instead of multi), I'm going to convert a 16" mutt rifle into an actual recce with a 16' Compass Lake Criterion barrel in 6 ARC, in mid length, and provide the CMC bolt for headspace.

The plan is to use a BCM Mk2 extension with an A5H2 buffer using a green Sprinco spring. I am trying to keep the OAL down but cannot find any compensator or flash hider in either 6.5 or 6 with 5/8 threading that's small enough. I thought that the Vltor one would work but that threading on it is weird. Not sure if it's a typo or not but my Compass Lake is in 5/8. Any suggestions? I saw that Alexander had a 6.5 A2 but it's no longer being produced.

Are you going to run it suppressed? Barrel length is up to you--but I will give my .02. It all depends on how far (realistically) you plan to shoot and how you have it set up. Have you given thought to a pinned 14.5? It would allow a complete rifle (recommended) without another stamp.

As far as gas systems go this is my experience. I have a 24" barrel with a rifle length gas. Even though I have an adjustable gas block I had a time with mine being over gassed. I ended up using an H2 or H3 and an XP spring to slow everything down enough. I had seen before that many manufacturers were doing rifle +1 or rifle +2 lengths, and after using a regular rifle length I can understand why. While I don't know exactly, my hypothesis is the amount of powder and resulting gas is more--a whole lot more--than I was originally expecting.

Long story short, I don't know if it's a universal thing, but I would plan on erring on the side of getting much heavier buffers, especially if you plan on running a can.

As far as muzzle threads go, they will be 5/8. Most places do not make anything 6mm. Been down that rabbit hole before. 6.5 works great and I would think even a 30 cal would be ok. I have Griffin mounts on everything as that's what my cans are. My 6 ARC one is a 6.5mm version. They do make several. That said, if you just want a plane jane A2 style, go with a 30cal. I am not sure how it will impact 'flash hiding capabilities' but it will definitely work on your barrel should you go that route.