Building a .308 AR and need some hints

[Charlie98]

I'm building a .308 AR for my TaeKwon-Do instructor, I built him a AR-15 a few years ago, but he wants something bigger for piggies. He already has an AP upper and lower, stripped. I have a few questions...

1) What is a good barrel/length/gas system setup for a hunting/blasting .308? I have a 16" M1a, it's fantastic... but I'm thinking something more like 18" for his build.

2) Does anyone have experience with Magpul mags in the AP lowers... do they work well? Is there a better alternative?

3) Coming off AR-15 builds... are .308 BCG's pretty much the same, besides the finish? Like I said... I'm new to the .308 stuff, and I know some parts are proprietary.

I'll take any and all hints and suggestions. I'm not sure if he is going to put optics only on it, or any of the finishing touches, but I need to research the main components so I have some suggestions for him.

Thanks!

 

[C-grunt]

The biggest suggestion I can give is if he already has an upper and lower, buy your parts from that company. There is no industry standard yet set for AR10s so parts dont always fit/work together when using multiple companies.

 

[Charlie98]

The biggest suggestion I can give is if he already has an upper and lower, buy your parts from that company. There is no industry standard yet set for AR10s so parts dont always fit/work together when using multiple companies.

No, I know that already. In hindsight, I would have just recommended he buy a complete rifle... but he presented it to me as a fait accompli.

 

[bfoosh006]

18" middie barrel minimum... IMO

Buy the Lower and upper parts kits from Aero.. that assures the correct bolt catch, pins ..etc. ( Lack of a Milspec guideline thing. )

Strongly consider an Adj. GB... I prefer SLR's

I also prefer heavy buffer weights and Tubbs .308 recoil springs.

The various "carbine" length stock patterns are not interchangeable... IE Standard AR15 carbine buffer tube REQUIRES the use of a 2.5" buffer ( DPMS Pattern ) ... a longer Vltor length buffer tube ( Armalite pattern ) requires the use of a standard AR15 carbine buffer 3.25" .

As mentioned... I use heavy buffer weights.. 5.3oz in a 2.5", H3 in a 3.25" and I use a 9.3oz in rifle length buffer tubes,

I use heavy because those "pause" the unlocking of the BCG, by just milliseconds, allowing for extraction at lower chamber pressures. A plus for .308 sized AR's.

I prefer to lap the upper receiver face "true" ... seems to help group size and sure won't hurt anything.

 

[berettaprofessor]

Listen to bfoosh006. Especially about the heavy buffers and the Tubbs springs. His advice helped me solve some problems when I was doing mine.

 

[FL-NC]

I would go with a 16" barrel and the lightest and skinniest rail and stock I could find. Mine has a MWI MLOCK rail. These guns (AR10's) will sneak up on you in terms of gross weight during the build process, and surprise you with a boat anchor at completion. As far as 7.62 Pmags, I have used them and found them very reliable in KAC SR25s and M110's, Larue OBR, DPMS SASS, and my custom AR10 I made from a vanilla Delton host rifle. The one absolute I have found to be true of all AR10's is that the BCG needs to be well lubed if you want reliable operation. For this, I strongly recommend a grease type lube like white lithium grease from auto zone. Or if you want to spend $ on name brand stuff, use TW25 or frog lube, but I'm going to save my $ and use the auto zone product. Liquid lubes aren't as sticky, and will fly out of the rifle when you fire it, which will put that oil on the outside of the gun, your glasses, etc.- in other words, places where it isn't needed and won't do anything for the reliability of the rifle.

 

[Varminterror]

In general, if I’m carrying the extra weight of an AR-10 and burning the extra powder of a short action cartridge instead of a mini-length in an AR-15, then I generally want enough barrel to make use of it. A lot can be done, especially pig hunting at short ranges, with a 16” carbine, but I generally prefer a 20” tube. If I’m suppressing, then I might use a shorter barrel to keep OAL down, but I’m no door kicker, I just hunt, plink, and compete with my rifles.

I prefer 15”-18” handguards, as I prefer more room on the guard, more stability on a bipod, and the aesthetic of a hidden gas block. The SLR Helix is one I like.

Adjustable gas block and full weight carrier and buffer.

I prefer carbine stocks, specifically the UBR, but fixed stocks can be just fine (XLR, Luth-AR, PRS. I don’t love A2’s).

Geissele trigger - G2S-e on a budget, Hi-speed NM if not. SSA-e is good as well.

Magpul mags are fine. I prefer stainless steel body mags when I can, but Magpul mags are fine.

 

[James Fonteneaux]

I bought a Windham Weaponry SRC a few years back, and have added an Advanced Armament muzzle brake and a Burris AR 532 prismatic sight. I second the statement above to run it wet. Magpul mags in multiple sizes work fine.

Edit: The brake is LOUD to the sides and behind, but definitely helps keeping rounds on target.

 

[someguy2800]

My experience with AR10’s is limited to having built one from scratch and handling others in the store, but if I may I’ll offer my opinion.

Compared to an AR15, AR10’s are fat heavy pigs. They are substantially bigger in ever dimension than an AR15, so they loose almost all of the compact handling that endears the AR15 to me. The receiver is wider, longer, taller, and much heavier. It would be pretty easy to end up with a 12 lb rifle with scope if your not conscious of weight with an AR10, so I would focus on keeping it light and compact.

If I could do mine over again I would not have built one at all, rather I would have just bought a DPMS gen 2. They are substantially redesigned to be very close in size to an AR15. If someone were to hand you one in the dark you really would not be able to tell you were not holding an AR15. If I had done that I would most likely still own it, but I did not like the AR10 I built so I sold it and built another AR15 in 358 yeti.

 

[Tommygunn]

My experience with AR10’s is limited to having built one from scratch and handling others in the store, but if I may I’ll offer my opinion.

Compared to an AR15, AR10’s are fat heavy pigs. They are substantially bigger in ever dimension than an AR15, so they loose almost all of the compact handling that endears the AR15 to me. The receiver is wider, longer, taller, and much heavier. It would be pretty easy to end up with a 12 lb rifle with scope if your not conscious of weight with an AR10, so I would focus on keeping it light and compact.

If I could do mine over again I would not have built one at all, rather I would have just bought a DPMS gen 2. They are substantially redesigned to be very close in size to an AR15. If someone were to hand you one in the dark you really would not be able to tell you were not holding an AR15. If I had done that I would most likely still own it, but I did not like the AR10 I built so I sold it and built another AR15 in 358 yeti.

I have a Saint "Victor" in .308 and it is pretty light, near enough to my AR-15s, while my D. P. M. S. LR-308 is, yeah, a heavy fat pig. But I still like it anyway.
Granted both are factory guns, but the AR-10 can be a light weapon.

 

[earlthegoat2]

Once I started toying with 6.5 Grendel, I forgot I had an AR10.

Just a heads up for the OP after he gets this build done for the sensei, there will be another upper or full AR build for 6.5 or 6.8. Haha.

 

[Charlie98]

Well... I have a stripped lower in the safe that will be my next AR build, probably in 6.8SPC. I chickened out last time and built another 5.56mm.

Some of you guys mentioned an adjustable gas block... I would never have thought of that. Good idea.

It's interesting... everyone I've talked to about the AR-10 either loves them or hates them, there is very little in between. Weight is often an issue, as is reliability.

I bought a Windham Weaponry SRC a few years back,

I looked at one of those, too, a few years ago... I thought it was a very well built rifle for the price. I talked a friend of mine into a WW AR-15 last year, it cost a little more but it appears well built, and he has had no problems with it so far.

 

[MTMilitiaman]

I'm building a .308 AR for my TaeKwon-Do instructor, I built him a AR-15 a few years ago, but he wants something bigger for piggies. He already has an AP upper and lower, stripped. I have a few questions...

1) What is a good barrel/length/gas system setup for a hunting/blasting .308? I have a 16" M1a, it's fantastic... but I'm thinking something more like 18" for his build.

2) Does anyone have experience with Magpul mags in the AP lowers... do they work well? Is there a better alternative?

3) Coming off AR-15 builds... are .308 BCG's pretty much the same, besides the finish? Like I said... I'm new to the .308 stuff, and I know some parts are proprietary.

I'll take any and all hints and suggestions. I'm not sure if he is going to put optics only on it, or any of the finishing touches, but I need to research the main components so I have some suggestions for him.

Thanks!

1.) I bought an Aero Precision M5 used because I got a good deal on it. I only have a couple hundred rounds through it but it has been flawless. Mine has a 16 inch 4150 CMV barrel with a midlength gas system. If I was going from scratch, I would have went with the 18 inch and a rifle length. For hunting, a 20 inch might even be better. But I think the 18 inch is probably most useful for AR10 because it is most compact that will take the rifle length gas system, and getting the longest gas system possible helps with DGI guns.

2.) I had some problems with Magpuls slipping over the mag release and falling out. I contacted Aero and they sent me their "enhanced" components, for free, even though I wasn't original purchaser. I installed their components and haven't had any problems since. I run exclusively Magpul 25 rounders because they are what is cheap and available in my area.

3.) Can't speak to BCG.

Aero's Customer service has been very responsive in my experience. Don't be afraid to drop them a line with any questions you have. If you are on Facebook, they have an Aero Precision Owners group that is really good for comparing notes and asking questions as well. Most people seem pretty happy with their Aeros.



Regarding weight, I don't think the AR10 is bad at all. According to my bathroom scale, my Aero is just over 9 lbs unloaded, with the Trijicon TA11J, and the Magpul two-point sling. A loaded 25 round PMag jumps it up to about 10.5 lbs. Plus it is fairly compact and well balanced. It isn't a poodle shooter, but it is no "hog" and those of us who seek the power of a 7.62mm usually understand it comes with some weight.

 

[Shawn Dodson]

I assembled a .308 AR-10 rifle using Aero Precision M5 receivers and Aero parts kits (without trigger). However instead of the Aero bolt stop I installed a Phase 5 extended bolt release (EBRV2/308).

Receiver extension is Vltor RE-A5 with H3 carbine buffer, JP Rifles rifle length buffer spring (JPS-OSR .308), and Magpul ACS-L carbine stock. I used a Primary Weapons Systems ratcheting castle nut and receiver end plate.

BCG is Toolcraft NiB (from Arm or Ally). No need to spend extra money for a boutique BCG - Toolcraft is good-to-go. (FYI, the BCG is the heaviest component on an AR-10.)

Raptor charging handle.

Barrel is Faxon 20" Big Gunner .308 (rifle length gas) with SLR Rifleworks adjustable gas block and Precision Armament M-72 compensator.

Handguard is Midwest Industries 15" DPMS high M-Lok (MI-308SS15-DHM). It has 5 QD sling mounts milled into the handguard so no need to buy QD mounts.

Trigger is Geissele Super Dynamic -Enhanced.

This rifle weighs 7 1/2 lbs without optic.

I fitted an SWFA SS 10x fixed power MOA turret/reticle scope using a Warne 20 MOA Extended Skeletonized 30mm MSR mount.

With the adjustable gas block, muzzle brake and buffer spring I used this rifle recoils less than an SKS. Recoil is negligent.

 

[Jessesky]

I built a 308 AR-10 recently. The platform is great but there is a major plaguing flaw. There is no one standard pattern of parts.

If building from scratch you need to research what fits what. And DPMS vs Armalite, and now PSA. Even if you stick with DPMS sometimes different brands don’t play nice with others. It’s a bit of trial and error.

Maybe I had a bad experience.

Nothing is ever guaranteed to work with any gun. But new parts work consistently far more on my AR-15 than AR-10. I always find myself needing to tune new parts for the AR-10