Adventures in building a .308 AR

[Idz]

After building several AR15s from 80% receivers I decided to try a 308 Win style AR build since the 308 ARs are not standardized so it would be more of a challenge. I purchased an Ares Armor "80% AR-10 DPMS .308", an interesting name because "AR-10" is trademarked by Armalite and uses a receiver with a flat cut on the rear whereas DPMS uses a curved receiver rear similar to the AR15. For the upper I got a Palmetto PA10 "modified DPMS" kit since I discovered the PA10 takedown pins would match the Ares locations on 6.880" centers.
Ares provides no information on machining their receiver so the 1st problem is where to locate the trigger group. Ares did drill out the selector indent hole which must match the location of the selector so the standard AR15 trigger group can be machined relative to the selector location.

After machining and assembly the following problems where discovered:
1) The PA10 takedown pins are too short by about 1/8" but are useable. I'll just make some proper pins.
2) The lower won't rotate on the front takedown pin. About .015" had to be filed off the lower to allow rotation.
3) The PA10 uses a roll pin to attach the bolt catch, the Ares uses a threaded pin. I made a pin from a 6-32 screw.
4) The bolt catch would not release the bolt. Apparently the PA10 catch is located out about 0.1" further. An AR15 catch works fine as does filing a chamfer on the PA10 catch so it doesn't hit the upper receiver OD.
5) The PA10 upper is tapered to AR15 width around the trigger group whereas the Ares lower is not. This is a non-critical 'looks' issue.

With these minor modifications the Ares lower mates nicely with the PA10 and fires flawlessly.

[nicholst55]

What you describe is the primary reason that I haven't built a .308 AR yet - too many variables, unless you use just one manufacturer's parts.

[xacex]

I put one together with an 80% lower, but went with standard LR-308 style, and parts. I had no issues with the build using parts from several manufactures, but I did stay away from anything that was oddball like Palmetto's stuff. I ended up with a pretty light 308 using a DPMS lightweight stripped upper, and combining that with a CMMG MK3 18" barrel which has a nice lightweight profile. I got under 8 pounds with iron sights unloaded, but I notice it is much more difficult to keep on target from the bench. Standing, or prone are about the only way to achieve good accuracy. Next one will weigh more.

[Fishman]

What is oddball about Palmetto's ar10 stuff? Serious question because I am considering building one and I was very satisfied with the ar15 build my son and I did using their parts.

[Electric88]

I thought about building a 308 ar off of an Ares armor 80% lower. I got a really good deal on a matched billet receiver set, and quickly changed my mind on that. Still not completed yet though, as it takes a bit more money to get into the 308 game

[Sticky]

I have built two AR's in 308, both DPMS style and both a mix of individual parts, starting with CNC'd 80% lowers that were made to match the DPMS std 308 upper.. both work flawlessly, no issues with either build. Both used std DPMS style lpk's which had all the proper parts and no fitment issues (308 bolt catch, threaded bolt catch pin, takedown and pivot pins were fine as well.)

[tygar]

I've been sitting on a Armalite AR10 lower for several years. Need to find an AR upper unless I want to do some machining to get it to mate to DPMS etc. Just can't decide whether I want an entry type gun or target/match. Have a Armalite A2 & a M14 with a BM59 folder & shorty barrel + a couple NM M14s. So, just can't make up my mind.

Anyhow, the point is Brownells has the Aero upper/lowers on sale but I haven't researched them & wondered about their "quality" & compatibility with other AR308s.

Not trying to jack the thread but if posters could evaluate the various upper/lower options & post it like the OP (thanks for the info by the way) we could get valuable insight about making one.

[gitu1]

I've only built one AR10. Used stripped DPMS lower and upper. Don't remember the maker of the parts kit. Stock is a Magpul. The handguard is carbon fiber. I got an 18" match, fluted barrel from Black Hole Weaponry.

It is pretty accurate. Was working on the load development for 800 yrds. when I moved (no longer have access to a 1000 yrd range). Used it hunting mule deer a couple seasons before the move.

[Sticky]

Not trying to jack the thread but if posters could evaluate the various upper/lower options & post it like the OP (thanks for the info by the way) we could get valuable insight about making one.

Glad to put my info up... I have done two, both DPMS (because it seemed like that was the most obtainable parts-wise a couple years ago when I built these). The lowers were done from 80% CNC'd based on a DPMS lower that came from a DPMS 308 rifle, so I know it was done to spec for a DPMS upper receiver, or compatible and matched up with the prints for a std DPMS lower receiver. I built the first to be a longer range rifle, the second to be a bit more of a tactical rifle (shorter bbl, lighter, more maneuverable and without a long range scope).

Here is the list of the major parts used on each...

308 Build "The Exterminator"
CNC Lower (mine)
Jard 3# adjustable single stage trigger
JP LMOS BCG
CMMG Upper
JP 22" Supermatch Bbl (1:11)
JP adjustable gas block
JP Std Compensator (blended)
JP 18" Modular handguard
Ace Skeleton Stock
Std AR 308 Rifle Buffer
Std Buffer Spring
Ergo Grip
Vortex 6-24 x 50 PST
Burris PEPR QD mount




308 #2


CNC lower (mine)
SAA - Billet LR-308 DPMS Style Upper Receiver
ALG ACT trigger
WMD bolt carrier assy NiB (Radical Firearms)
Black Hole Weaponry 18" poly 3 groove bbl, SST (mid length gas) 1:11
JP 15" modular handguard
BCM Mod 4 Gunfighter CH
Std buffer/carbine buffer tube/spring
YHM Flash hider/suppressor mount
YHM flip up sights
DD Enhanced Buttstock
Burris AR-332 3x prism sight (waiting on Vortex 1-6 Strike Eagle w PEPR QD mount)

The first build - The Exterminator... lol



The upper/lower mating...



The second build... I need to get some better pics of... sorry, only have a couple and they don't really show it well. I'll get on that this week.

Main difference, which most are aware of, is the difference between an Armalite AR-10, and the other variations of the 308 in an AR platform, as there is no std or mil-spec... so DPMS is different that Armalite and some of the others as well. Be sure, if you are building one, that your bbl style, upper and lower styles all match up, or yer gonna have some issues... big ones.. lol.

I haven't messed with the PSA stuff in 308, so I can't add to that, though I have ordered many things from PSA with no issues at all.

[Rustyleee]

Being a truck driver I listen to a lot of pod casts. I use the Stitcher app on my android and have found an AR15 podcast dedicated to those that are builders. Last week they had a fellow on from http://308ar.com/
It seems the difference in manufacturers is where the problems lie.

[tygar]

I have been debating just selling the Armalite lower & get a DPMS set & go from there.

Gitu your DPMS was able to take about any brand parts, correct? Same with you Sticky? Cool rifle! I have been told that with the Armalite & need an AR upper or it's a real circle jerk & they are about twice the cost of DPMS.

What about mags? I have about 20 AR10 mags & a whole lot of M14s so I would like to not have to get a bunch of "other" brand mags. What mags fit all you guys rifles?

Still would like some info on the Aero Precision Upper/Lower that Brownells has on sale. Sure wish I had got the DPMS when CDNN had them on sale.

I do know that I don't want to mess with completing a receiver, I want to get them complete.

[Artful]

What about mags? I have about 20 AR10 mags & a whole lot of M14s so I would like to not have to get a bunch of "other" brand mags. What mags fit all you guys rifles?

There are three main styles of magazines in the .308 AR's, and a mythical 4th.

From Most prevalent to least:

Original AR10 style mags (including KAC mags, and PMAG-LR)
KAC
LMT
Larue
DPMS
LWRCI
Sig 716
2013 Armalite
2013 Bushy
2013 S&W

Eagle Arms/Armalite AR-10 a modified M1A/M14 style mag
Pre 2013 'new' Armalite AR-10
Noveske N6

Hk417 mags
Hk417
MR308


FN FAL Metric Mags
~2006 Bushmaster -- not sure if any actually shipped other than SHOT demo models

Note:
M-14 mags: Armalite/CMI manufactured mags are pricey ($45) and true M-14 mags, while plentiful and of varied quality, must be converted with a milled slot. M-14 mags cannot be switched back and forth between the AR-10 and M-14 due to different followers (if you want the bolt hold open feature to work).

AS I Remember: DPMS mag has a narrower, but with a larger standoff, rear rib, than the current Armalite mag.

The DPMS mag is also more square than the current Armalite mag, and is of very similar overall dimensions to a G3 mag.

I believe the mag catch height to be compatible.

I believe that the DPMS bolt catch would work in an Armalite lower; I'm not sure about the other way around.

Bottom line: You can't put an Armalite mag into a DPMS lower because the rib is too wide at the back, and I believe the main mag is also a little too long.

You can't put a DPMS mag in an Armalite lower because it's too wide throughout, particularly at the front, because the Armalite lower is cut for the tapered Armalite mag.

I believe that you *could* cut an Armalite style lower to accept DPMS/SR25 mags. However, today's attempts at interchange suggest that an attempt at a jack of all (AKA a magwell opened up to allow for either to work) would probably be proverbially master of none, and would have to have the mag-locating features opened up so loose that both mags would slop around and probably have trouble.

On the assumption that DPMS mags are entirely compatible with SR25's, I would assume that the same would be true of the SR25 mags. Unfortunately for me, I don't know anybody who actually has one of those and I have not jumped into AR-10's myself.

I myself would want to copy as closely as possible the M110 that is made for the Military. Realistically the 7.62 AR standard mag is the KAC Mag based on the original Gene Stoner AR10 magwell. And with over 17,500 SR-25 style guns (M110/Mk11/M110K1) shipped to US and Allied governments - and at least 10 mags for each gun sold - its pretty much been solidified by the introduction of the PMAG-LR by Magpul.

[Electric88]

I have heard excellent things about Aero Precision's receivers. I bought a Next Level Armament receiver (it is also DPMS pattern), so I haven't conjured up the funds for another build yet. In all honesty tygar, I would probably sell the Armalite receiver and jump into a DPMS pattern receiver, or a Mega Maten set if you have the money. There is far and away more support for DPMS patterned rifles, whereas I think there is only a handful that support Armalite (Noveske is one I know that does, but they aren't for someone with even a modest budget).

As for mags, Magpul makes pmags for 308 rifles that are compatible with most (if not all) DPMS pattern rifles. That's what I would run.

[M-Tecs]

I wonder if the Ruger Precision Rifle mag system could be incorporated into an AR10?

[Electric88]

I don't remember reading what mags the Ruger Precision Rifle uses. It would be awesome if they picked up on using Magpul pmags for 308 though

[Sticky]

Tygar, yes the DPMS patterned 308 can use most any parts that are designed to be compatible with the DPMS design. Unlike the AR-15, there is no 'spec' for the 308. Armalite was first and patented their design, so others that came along had to modify it to avoid infringing. The military never adopted a standard and created mil-specs, as they did with the AR-15. You can make anything AR-15 work, even with a lot of deviations from a mil-spec receiver, as long as you hold the critical dimensions and areas to spec... The 308 does not share that nice feature, so there is a myriad of variants.

The upper, lower and barrel all have to match up for the two primary styles of 308's, the Armalite and the DPMS/SR25. I do think that parts availability is a little better for the DPMS style and also the prices are a bit lower for some of those vs the Armalite. I don't really see any functional differences, nor benefits one way or the other for one platform over the other, except for pricing and availabilty of parts.

I used primarily JP rifles parts on the upper for the Exterminator.. barrel, handguard and BCG were all from JP Rifles. The second build has more of a mix of parts, with the BHW bbl, JP handguard and a WMD bcg. Both the SAA and CMMG uppers mated fine as well as another I helped a buddy build on the same lowers, but with a std DPMS upper.

I run Magpul mags, no issues and this is from their website for the M3 mags....

Additional commercial rifle compatibility includes the new Armalite AR-10A, Bushmaster .308 ORC, Colt LE901-16S, CORE Rifle Systems CORE30, DPMS LR308, JP Enterprises LRP-07, KAC SR25, LaRue OBR, Les Baer .308, LMT .308 MWS, LWRCI REPR, Mega Arms MATEN, POF P-308, Remington R-25, Ruger SR-762, S&W M&P10, SIG716, and others*

*NOTE: NOT compatible with Armalite AR-10B, Noveske N6, Springfield Armory M1A, Rock River Arms LAR8, FN SCAR 17S, PTR-91, HK417 or any other rifles that utilize M14, FN FAL, or HK 91/G3 patterned magazines.

I have used Aero uppers on AR-15 builds and they worked just fine, no issues. I would not hesitate to use another (in fact I have one tucked away somewhere) for an AR-15 build.

The LPK for a 308 is very similar to an AR-15, but beware, while the trigger parts are interchangeable, the takedown and pivot pin are longer and larger, the bolt catch is different and you really should run the proper bolt catch. The bolt catch pivot pin is normally threaded in on a DPMS lower, not just a roll pin like on a std AR-15. The grip is a bit different for the 308 lower also, due to the takedown pin spring and detent going down to the grip, not out back through the buffer end plate as on an AR-15, so beware when fitting a grip, needs two holes instead of one for the spring/detents to rest in.

I have been running my tactical BHW bbl'd 308 to test lead boolits with great success so far. Still working a bit on load development, but I have had great luck running the NOE and MP 30 hunters in my AR platform 308

[tygar]

QUOTE: I run Magpul mags, no issues and this is from their website for the M3 mags....

Additional commercial rifle compatibility includes the new Armalite AR-10A, Bushmaster .308 ORC, Colt LE901-16S, CORE Rifle Systems CORE30, DPMS LR308, JP Enterprises LRP-07, KAC SR25, LaRue OBR, Les Baer .308, LMT .308 MWS, LWRCI REPR, Mega Arms MATEN, POF P-308, Remington R-25, Ruger SR-762, S&W M&P10, SIG716, and others* QUOTE:

So the Magpuls will work in a lot of 308s. THats good.

So if I get the Aero I will need to ensure that it is compatible with DPMS style mags & parts in the .308 build just like their AR15s.

I think it would be of benefit if I can get a complete lower assembly to start, given your info on takedown, pivot pins, bolt catch, etc. then decide on the upper configuration I want.

Thanks guys, great info. IDZ your post is what got me wondering about compatibility of these things.

Sure would be nice if they were as interchangeable as the AR15s.

Thanks
Tom

Lot of info from u guys.

What I have come to realize is that I need to sell the AR lower & I think my AR10 A2 & get into another one, preferable a DPMS style & be done with it. The cost of all parts will be much lower & also availability greater. (I tried to get a front site elevation tool from AR & they don't even have them any more)

[Electric88]

Aero Precision lowers are compatible with DPMS pattern parts. I'm sure you can find complete lowers somewhere, I'm not sure where. As for the lpk, there are definitely some differences between the ar15 kits and ar308 kits (as sticky noted), but you can buy ar308 lpk easily enough. Just make sure they specify that they are for the 308 and you will be fine. Also note, that if you choose to build your lower, you will want a 308 specific buffer assembly (I believe the 308 buffer tubes are a bit longer, as well as the buffer. If I'm wrong, hopefully someone will step in and correct me promptly). However, if you are going to buy a complete lower then you will be fine. I'm not sure what you intend your build to do, but I highly recommend the Luth MBA-1 stocks. They are half the price of the PRS, but lighter. I thoroughly enjoy mine

[Sticky]

A 308 lower parts kit will fit a stripper lower, as electric said and the Aero lower will be compatible with all the DPMS stuff, including the pmags, I'm sure. It's as easy to build a lower up if you get a stripped one, as it is an AR-15, there are but a few subtle differences.

The buffer tube is the same as used for a collapsible stock on an AR15, BUT you need to have a proper AR308 carbine spring and buffer. THEY ARE DIFFERENT than an AR15. An A2 rifle stock uses the standard AR-15 rifle buffer. The carbine buffer is shorter, due to the longer bcg in a standard AR15 tube.. that is just how they do it.

I have run a slash heavy buffer in my carbine as well, but with slightly reduced lead loads, I had issues, so swapped the carbine out to a standard buffer and all has been fine. The heavy worked well with jword loads tho..

I opted to build mine from 80%'rs as I have done a bunch of AR-15's that way and I live in a state where its better, imo, to not have to go through the hassle if you don't have to.. :zip:

[Electric88]

One thing I just remembered that you might want to watch out for when building the upper receiver group is that DPMS pattern rifles can have two different rail heights, high and low. I don't know that one is more standard than the other. Just make sure that when you buy a rail/handguard, that the height is the same between the two. I want to say offhand that Aero Precision uppers have the low height rails, but don't take that for gospel. I could very well be wrong, as I have looked at so many that it can run together