Alright, so I've been tossing around the idea of an M110K1 clone.  I'm coming to a bit of a roadblock here as parts selection and compatibility goes.

First off is the barrel.  To use the 7.62 URX 3.1, it is my understanding that I have to use a barrel with a rifle length gas system (both for "clone correctness" as well as this particular rail not allowing a LP GB underneath it).  So I'm left with either purchasing a ready made 16" .308 rifle gas barrel (not a lot of manufacturers) or having ADCO chop a longer one down for me (not a lot of info on reliable gas port sizes for this setup).

From what I can see, the only available ready to purchase 16".308 rifle gas barrel is made by CMMG.  It is 1:10 twist, 416 SS, and is nitrided.  Now, my question on this particular one is twofold.  One, it is my understanding that this is a DPMS style barrel (although I'm not exactly sure due to CMMG using their Mk3 designation, and not specifying what pattern it works with).  Secondly, I have no experience with CMMG barrels and there doesn't seem to be a lot of users of them out there (at least the SS .308 models).  Obviously accuracy is a very large consideration in this build, so what does everyone think about CMMG .308 barrels?  Any experience with them or accuracy testing to report?

My other option is obviously cutting a barrel down.  I would really prefer to use this option because I can select a barrel that I know will give me the accuracy I'm desiring as well as it being the correct pattern.  Only problem is gas port size.  I've searched and searched with nary a response as to what would be optimal.  To compound this issue, I don't have a local gunsmith who can do gas port work, so if I have ADCO chop the barrel, I'll have to re-assemble, fire to check function, and if it needs more work, I'll have to disassemble and ship it back off to ADCO.  Basically, this option seems like an enormous pain in the ass.  Does anybody here have ANY experience with 16" rifle gas .308 barrels?  If so, what gas port size worked for you?  I realize a functioning gas port size can differ somewhat barrel to barrel, but a "close enough" number would be awesome to have.  

My next issue is the BCG.  Most here recommend when doing a .308 build to use a BCG manufactured by the same company that manufactures your barrel.  So, CMMG does offer their Mk3 BCG for sale individually.  Only problem is, I'm back at this compatibility issue.  CMMG doesn't really specify what pattern it works with (other than it being designated as a Mk3) and my searching only turns up some vague posts about it being DPMS pattern.  Not exactly confidence inspiring.  So does anyone here have experience with using a CMMG .308 BCG in their DPMS pattern build?  Any compatibility issues to speak of?  Also, the CMMG bolt carrier doesn't feature FA cuts and my plan was to use Aero M5 receiver sets, which have a FA.  

Of course, if I go the "chop a barrel" route, this isn't an issue.  I'd probably use a Rainier Arms barrel and just use their BCG to go with it.

Lastly (and I know I already stated I was going to use Aero receivers), but does anybody know what .308 receiver sets would look as close to KAC in appearance?  I know that a few here have done some KAC .308 clones.  I could probably just search this question myself, but I figured since I was already starting a thread it wouldn't hurt to throw this question in at the end.  

In the end, if this turns out to be too big of a PITA, I'll probably just end up going with my original plan of a Mega Megalithic MATEN receiver set.  Just thought a M110K1 would be a cool clone if I was building a .308 AR anyways.  

Any and all help appreciated, guys.

For mine, I bought a 20" Krieger barrel and had Marvin Pitts cut it down to 16" and dimple it. He didn't mess with the gas port at all, and it will reliably cycle bulk military ball. The problem you run into with the rifle length gas set up is that most .308 barrels use Armalite length gas tubes which are slightly longer than the KAC rifle length.

Pics just because.

Ended up getting mine custom turned because is was pita finding what I wanted.

Buy this, change the rail = the real deal at a great price.

https://www.boltcarrier.com/product/sr-25-emc-special-release-grade-c/

I agree with this. If I could have it here. I would definitely get one of these.

I used a 20" jp barrel and BCG and cut it to 16"

If you order from Rainier you can have them cut and thread it before they ship it to you. I had them cut my Rainier select 20" down to 16" and it works great. The gas port is .100" and has cycled just fine with ball ammo. I use this on my Aero M5 receiver with the Aero BCG.

Pics or it didn't happen...

Well its not a KAC clone, but what the hell. Please excuse my crappy picture taking.

Awesome, thanks for the info man.  Glad to see a few here have had them cut down without any gas port work and they run fine.

Have you weighed yours at all?  I'm still debating on doing this clone vs. going with a MATEN Megalithic setup (which I understand is pretty damn light for what it is).  I understand it's a .308 AR so it's not going to be light either way, but I plan to carry this thing around occasionally and would prefer to get it as light as possible.

I would, but for the cost, I could easily save over $1,000 by doing this myself using non-KAC parts.  I'm just not in the market for spending close to $4,000 on a .308 rifle right now.  

Awesome info man.  I was wondering because I'd never seen a cutting/threading service on Rainier's website under their Gunsmith Services, but apparently it's possible.  

What scope mount is that?

Larue.

I suppose it'd depend on which one you were talking about.  There are quite a few different pictures in this thread showing quite a few different scope mounts.  Since you didn't quote a specific picture, it's kind of hard to give you an accurate answer.

This is my clone, I'd love to eventually get more Knights parts, but I'm poor.