AR10/.308 AR Build knowledge thread.

[polydeuces]

First:
For those wanting to get to the 'meat-and-potatoes' immediately, go to post #59 page 6 - a comprehensive list of what needs consideration - what works and what does not.

If you're capable of building an AR15 and are comfortable doing it there's no reason whatsoever you could not build a reliable AR308.
The same basic concepts apply:
First and foremost - stick with reputable, quality parts. Know where NOT to go cheap.
Do your homework - research to make sure the parts you get play well together.
Use the knowledge of this forum, together with much in this thread there is little gambling or guess-work left - that and use the search button.
The info is available, and if not sure ask - do not assume - there is no TDP; variations and exceptions are the rule.

For more details and deeper discussion read the OP/thread as originally started:

The itch needs a scratch. Want to build an AR10/.308n platform rifle from scratch.
Having done research one thing has become glaringly clear: there is no standardization as with AR15. Wondering if we can build a basic knowledge thread?

There is a significant increase in offerings of quality receivers, now raising the question is with which parts they play well together?
So we have 2 different patterns:
Armalite AR10
DPMS/KAC SR25

For instance; PSA, Aero Precision - both DPMS pattern- offer receivers, barrels, BCG's on their websites. What if I want to get a 3rd party BCG because of different specs - carpenter 158 vs 9310 bolt.
Then - I assume the AR10 BCG will not run in a DPMS pattern set up?

What about barrels - will any DPMS pattern receiver play well with any DPMS pattern barrel/BCG, and how concerned should we be about 'headspace' fit and functionality?
I know from experience that when purchasing known quantity AR15 parts this will as a rule fit as a glove, across makes.

There may be a bit of tweaking involved getting the ideal spring and buffer weight to get it running smooth - but that's the fun part.

Not looking for product info or validation, really trying to get more input on what works and won't work with what platform, and where there is cross-platform functionality.
For instance - magazine are dedicated to platform, while most parts of the LPK's fit across the board, even .308/5.56.

Am I missing and or should I be concerned about anything else? What else can we add to this?

UPDATE:
Trying to keep this up to date I have edited the OP, and will continue to add info as it becomes relevant on 'brief recap' post #59, page 6.

[SeriousStudent]

This thread is relevant to my interests. I am seriously considering a 7.62 gas gun, and would like to build one with an Aero Precision upper/lower and a BCM KMR rail. I had not decided on a BCG or barrel yet.

I'll be quite interested in what you come up with.

[archad]

AFAIK there is no BCM KMR for a 308 gas gun yet.

[SpookyEng]

I am awaiting delivery of Aero Precision Lowers, uppers (std and the M5e1 w/KeyMod rail) BCGs and LPKs. I also have a PSA lower and am awaiting a PSA rifle build kit (eta Monday). The plan is to compare the two offerings and offer my first hand evaluation. I also plan on checking compatibility between the two. As far as barrel and bolt go, as long as they are both the same configuration (DPMS or Armalite) they "should" be compatible. The build will be using the BAD ASS ST, SSA-E trigger, and Troy Ambi mag release with The AP lower to confirm their compatibility as well.

[Riddle]

AFAIK there is BCM KMR for a 308 gas gun yet.

you need a 7.62 specific rail (also there are receiver thread pitches and/or receiver to rail heights to consider)

[SeriousStudent]

Yes, I have my fingers crossed that BCM hears my plea, and makes a KMR for a .308.

But they are very busy folks, and I'm content to wait patiently. They currently producing much tasty goodness for me to enjoy.

[Kokopelli]

I'm in this as well.. I'm just waiting for the Black Friday sale's to hit. At the moment, I'm thinking I'll take the route of a cheap (PSA) lightweight carry handle carbine. Just something to get into the game with and play a little. Interesting that PSA seems to compete with themselves with the PTAC line. I've had good luck with the PSA premium line and will probably stay there for this build..

[TehLlama]

Yes, I have my fingers crossed that BCM hears my plea, and makes a KMR for a .308.

But they are very busy folks, and I'm content to wait patiently. They currently producing much tasty goodness for me to enjoy.

As much as I'd really adore an Aero Precision M5E1 setup with their 16" SS Barrel, I'm still waiting to see if BCM comes out with a KMR handguard (or complete .308 rifle system), if DD rolls something out (they already have a LR308 lite rail, why not an LR308 SLiM/V11 type handguard) I'd look at that; we know Noveske can make .308 barrels and complete setups, if they roll out with a flared SR25/PMagLR compatible lower, and matching upper I'd buy that system above all others; and even though every time I mention this somebody fails to read replies 'they already do' - LMT could release a non-MRP version since they already have the majority of the parts, but a Defender308 would be enough to nearly crystallize an industry standard.

I'd buy the LMT Defender308 if it came out, since that would probably be an LR308 type setup, and they'd mostly cement that as 'the' rifle since a Mike Rock (or other LMT quality cleared) barreled standard configuration that uses their existing lowers/CH/BCG/Sights but runs a conventional upper/barrel nut setup that would use existing handguards. Colt could do the same thing (make a non-boat anchor non-proprietary version of their SP901), but I don't see that happening.
DanielDefense seems to have the ability to hammer forge barrels in house if they want to shell out for some uber pricy mandrel and other stuff; can make handguards like nobody's business, and with a standard receiver design they'd be able to parts bin almost everything else on the rifle - for fairly lightweight V1/V5/V11 availability type entry into that market space it would be immediately successful, they'd cover a lot of market space, and again it would further stabilize the market for 308 AR configurations - their hunting modded Ambush V7 type version would also be a clear hit.
The BCM is the pink elephant in the room for what they could do (a 16" EMW mid-weight button rifle CMV steel setup with 13" KMR would rock, and adding a SS barrel in 16 or 18 like their KMR Recce would finish out that line - again BCM has the bolt-on stuff sorted out once they have the receiver pairs finalized, and the complete setups would be phenomenal and arguably worth the price premium.
Finally Noveske have made 7.62x51mm AR's, and I think they'd have the ability to come out with a few of the most lust-worthy components to base builds off of - a flared GenIII type lower, maybe work with VLTOR for a MUR-7.62 and then mate it to a revised barrel extension version of a PacNor 7.62 barrel blank in their NM type chamber and I'd be willing to throw enough aftermarket parts at it until I had the unicorn I wanted.

What realistically will drive it in the interim will be if somebody like RainierArms, MegaArms, HodgeDefense, LaRue, or maybe even an odd player like Geissele, S&W 'Performance Center M&P10' or Aero Precision to make part-together complete rifles that make enough sense and don't have any bespoke parts that might emerge as a go-to answer. Mega have the MA-Ten, API has their M5E1 proprietary integral Keymod handguard, and I think both of those are held back by requiring integration (where there are players like KAC, BCM, DD, Geissele, and even MI that make such great handguards that can bolt-on and therefore future-proof the platform). I'm not in love with the Fortis Rev rails on the Rainier Custom builds, but if they can source enough of good receiver pairs, LPK/BCG/Buffer setups and then put combos like the MI SS-Keymod with their UltraMatch SS barrels [or if anybody churns out awesome cheap keymod rails with integral QD cups] and choose flexible enough furniture sets, then it's a real winning answer. Same thing if LT magically got through their backlog to make a Stealth308 line of stuff, they'd have the tech to make it happen but they're so snowed in backlogs that they're unable to even use the PredatOBR upper to its fullest.

What may also get this rolling is a third party manufacturer finding a way to bundle all the LR308 specific LPK/Buffer/Spring setups and combine the rest of the missing components to have better and properly QC-ed completion kits for an LR308 receiver set. That retailer could throw a mildly absurd price premium and still get asking price because that's the part that seems to hold some of these platforms back - the charging handles seem to be sorted and there are plenty of good barrels; and a BCG spec will eventually emerge, but sourcing quality receiver pins, bolt catches, buffers, and the like is why I'm shying away from building one myself, just because the ammunition budget to shake out issues on the rifle is something I don't really want to spend the money to guinea pig just yet.

[Sticks]

Even a cross reference chart would be extremely handy.

Like the rest of you, I've been pondering a .308 AR platform, but come to a screeching halt because of all the "Proprietary" components on the uppers, and lowers.

DPMS now has a Gen II out (ironically appears to be a front runner - Tier I rifle, given that their 5.56 rifles are considered crap) which IIRC is incompatible with their Gen I - kind of stirs the confusion pot a little.

I think that we can agree that we want to see a standardized universal spec for the LPK, FCG, BCG, Charging handle, Barrel nut thread, Barrel Extension, and Mags. Rail compatibility comes down to low profile or high profile. At least they all use the same RE.

I suspect a lot of this comes down to the Mil does not have an AR-308 that they use - ergo no basic Mil Spec to go by from the manufacturer aspect, and gods forbid the top manufacturer's R&D departments get together and come to an agreement.

[archad]

I know Seekins doesn't get much love on this forum. Seekins just released their .308. I'm getting one they are local for me.
Seekins is fully ambidextrous. 18" Mike rock barrel with intermediate gas system. I shot the 1st 2 prototypes back in May.