8.6 Blackout AR10 Build

[BigNate]

I've been reading up on the 8.6 Blackout and decided that I needed to waste some dollars and build one.  Anyway - I went digging for info and found only two references - both of which were more focused on reloading for that cartridge - so I figured I'd start a thread... 


The gun will be an SBR and I'll be reloading for it and working on both sub and super-sonic loads.   The immediate purpose of this build at this point is to play with the cartridge.  I'm usually a "more is better" guy when it comes to guns as a tool for personal defense and the cartridge has my interest as something that could bridge the gap between the 45-70 lever gun that goes into the woods with me, and the AR15 by the nightstand.  There's a lot of ground to cover before this would replace either of those (both of which I trust with my life) - but the idea of very heavy bullets delivering more than their normally expected share of energy due to dumping the extra rotational energy is intriguing. 
 

I have the following parts so far(most of this is stuff that I have accumulated and has been waiting for a project): 

• Aero Precision M5 bare lower 
• Aero Precision M5 Upper (assembled)
• Ballistic Advantage .308 BCG (understand these to be Aero Precision units - the Aero was out of stock and BA had a good holiday sale going)
• Odin Works .875" adjustable gas block (was going Superlative Arms but a buddy had the OW unit available at a great price so I'm starting there).  Planning to try to make it work suppressed. 
• Radian Raptor SD 7.63 charging handle
• Wilson Combat 10.4" handguard (used - was on another aero based AR10 - will work for now) 
• Standard used lower furniture for the moment - once it is up and running I'll probably upgrade
• Larue MBT-2S 
• Standard lower parts kit

Stuff that I need to figure out:

• Buffer and spring
• Barrel
• Gas Tube (pending barrel selection)
• Muzzle device (will likely be a function of suppressor selection.  If I let myself do what I think I want to do I'll be ordering a SilencerCo Omega 36M - but the devil on my shoulder has not yet fully beaten down the accountant on the other shoulder)

So now - the questions: 

• Barrel Manufacturers - I find AR10 barrels in 8.6 from Faxon, Mos-tek, and PRO2A.  I know Faxon, but don't know the other two.   Mos-tek wants almost twice the price of the other two.  Unless I get a compelling reason to do so I'll probably just buy a Faxon as they are a known quantity.  I always want reasonable quality or better - but this is not a gun that will ever be shot at great distance and I doubt that I'd get a ton of value out of whatever makes the Mos-tek "better" (assuming that it is actually better).    Any other manufacturers to look at?  Any good or bad to say about any of these?   
   
• Barrel Length - This is an SBR build - so I'll be going shorter than 16".  I want a compact platform for carry in the woods and for all the other reasons that people want SBRs.  I'm leaning to 12" mainly based on what I see in the load data from Q (see below) and the fact that it gives up appreciably less velocity than the super short barrel in most cases.   Interested in input from the mob as to what I need to consider in this space.
  
  
  
   
• Buffer Tube, Buffer, and Spring.  This is an area where I really don't know where to start.  If I were going to just "guess" I'd start with the Aero tube/buffer/spring kit and go from there - but I'm guessing this is going to need something special.   Muzzle energy for the supersonic rounds above is in the 1700-2100ftlb range...   for the subsonic they are in the 700ftlb range.  Where do I start?  With the adjustable gas block I like to think that if I pick the right buffer spring and buffer I'll be able to shoot both sub and supersonic rounds through the gun with just a gas block adjustment - am I wrong?   Any advice on where to start with spring and buffer weight? 
  
  Thanks in advance... 

Edited December 11, 2023 by BigNate

[98Z5V]

8 hours ago, BigNate said:

 Any advice on where to start with spring and buffer weight? 

Go Big...

Start off with the Armalite AR-10 Carbine Receiver Extension Kit.  I'm just guessing, but I'd expect that you might need something heavier than the H3 buffer, but at least that will get you running, in the right direction.  Maybe a HeavyBuffers buffer, in the long run.

The Aero kit you mentioned is gonnd come with a receiver extension that 7.000" internal depth, it's only gonna work with shorty 2.500" length buffers, and the buffer you receive from Aero in that kit will weigh 3.8oz.   I wouldn't even use it, man.  The Armalite kit I mentioned will have a receiver extension that's 7 5/8" internal depth, run standard length carbine buffers at 3.250" long, it comes with the EA-1095 recoil spring, and the buffer is already an H3 at 5.4oz. 

If you can't find the Armalite kit, we can piece it together from known good quality parts, and achieve the same goal.  

Edited December 12, 2023 by 98Z5V

[BigNate]

This one? 

https://www.huckleberryarms.com/product-p/armel0370.htm  ?

It’s out of stock there -but if that’s the one I’ll dig a bit…

Edited December 12, 2023 by BigNate

[98Z5V]

1 hour ago, BigNate said:

This one? 

Nope, that's a rifle receiver extension.  You running a rifle stock, or carbine stock.  I figured carbine, collapsible stock, since you're going the SBR route.

[BigNate]

1 minute ago, 98Z5V said:

Nope, that's a rifle receiver extension.  You running a rifle stock, or carbine stock.  I figured carbine, collapsible stock, since you're going the SBR route.

D’oh… correct….  I’ll keep looking…

[98Z5V]

1 hour ago, BigNate said:

D’oh… correct….  I’ll keep looking…

This is everything under one part number, but I can't find it anywhere in stock. 

https://www.eurooptic.com/Armalite-AR-10-6-POS-Receiver-EXT-Kit.aspx

 

No worries, we can piece it together.  I'll link the appropriate parts to hunt down.

 

 

Edited December 12, 2023 by 98Z5V

[98Z5V]

Here's a blem VLTOR A5 receiver extension.  You'll never find the blem.  These are my go-to carbine extensions for large frame builds when I can't find the Armalite parts.   (I EDITED THIS, put the wrong link in here the first time...)

https://www.vltor.com/shop/ar/receiver-extensions/vn-re-a5-a5-receiver-extension/

Here's the recoil spring - either option will give you identical results.  If you can find the Armalite spring, it's the EA-1095 spring.  I can't find one right now.  The other alternative is the Sprinco Red spring.  This one:

https://www.primaryarms.com/sprinco-m4-ar15-carbine-red-extra-power-carbine-buffer-spring

^^^ Don't worry about the description that Primary Arms listed there.  That's the one you need.

Any old AR15 H3 Carbine buffer.  Literally.  As long as it's an H3, you're good.  This one will work:

https://www.primaryarms.com/expo-arms-h3-ar15-carbine-buffer-od-green

 

Those parts will get you up and running.  The only thing that might change is the buffer, depending on how much of a Beastly Thumper this thing is.  At that point, if it happens, I'll point you towards an even heavier buffer from HeavyBuffers.com. 

Here's what Sprinco says about their Red spring:

RED SPRING

Extra Power Buffer Spring. This was our first AR buffer spring solution that we were tasked to design back in 2006 for a Force Modernization Team to specifically address spring-related M4 carbine reliability function issues for operating challenges in the Eastern Asia Theatre. The design loads of the Red spring are approximately 25% greater than the White spring for one of the considered Load Constants in the spring design. Refer to provided tuning procedure reference documents prior to calling for recommendations for use. The Red spring is commonly used in 9mm, 6.8 SPC, 6.5 Grendel, .450 BM, .450 SOCOM, .500 Beowulf, and Colt LE6920’s specimen carbines, but certain specimen guns can deviate from the norm depending upon port values and the power factor of your chosen ammunition loads. Color Coded RED.

NOTES: The RED spring is appropriate for moderately gassed .308 / 6.5 CM / .260 Rem heavier caliber carbine platforms using AR-10 / SR-25 Pattern (Armalite, LMT, LaRue, KA.C, etc. receiver extensions and 3.25” carbine buffers. NOT for use in “DPMS Pattern”.308 Carbines using standard 7" deep M4 extension tubes and short, 2.5” buffers. (Use our "ORANGE” Spring" for that specific platform approach application.)

 

Edited December 12, 2023 by 98Z5V

[98Z5V]

Bump - had to make an edit, for the wrong link I posted for the VLTOR part above...

[BigNate]

Thanks much….  I’ll be ordering tomorrow.   

 

[Magwa]

and a tax stamp......... lol

[BigNate]

13 hours ago, BigNate said:

Thanks much….  I’ll be ordering tomorrow.   

 

Edit - OK - not ordering today - I decided to try to hunt down one of the Armalite AR-10 Carbine Receiver Extension Kits.  I really can't start building until I get the barrel here and it's not ordered yet so I've got a few days.   If I manage to find one of those "kits" - does the included spring and heavy buffer - or is it just the tube?  

2 hours ago, Magwa said:

and a tax stamp......... lol

Got it covered... 

[shooterrex]

The armalite kit is everything but the butt stock.

[BigNate]

36 minutes ago, shooterrex said:

The armalite kit is everything but the butt stock.

Thanks much... 

 

Also - barrel ordered and inbound... went with this : Faxon Barrel

[BigNate]

I went looking for available commercial ammo and found some.  It's not cheap - but I will be buying at least a box or two of factory loads for "break in" of the rifle.  Well  - not so much to actually break in the rifle - but to take load workup variables out of play for the first few rounds through the gun... 

 

Anyway - stumbled on these - which immediately led to "I've got to source a block of ballistic gel..."  🙂

 

350 gr Supersonic

 

[BigNate]

OK - parts either in hand or in the mail include: 

Item	Family	Brand	Description	MPN
Lower Receiver	Lower	Aero Precision	M5 (.308) STRIPPED LOWER RECEIVER, SPECIAL EDITION: FREEDOM - ANODIZED BLACK	APAR308053C
Trigger	Lower	LaRue	LaRue Tactical MBT-2S Trigger	MBT-2S
Buffer	Lower	Expo Arms	Expo Arms H3 AR-15 Carbine Buffer with OD Green Bumper	XP-H3B-AR15
Buffer Spring	Lower	Sprinco	Sprinco M4 / AR-15 Red Extra Power Carbine Buffer Spring	25004
Buffer Tube	Lower	VLTOR	VLTOR, Receiver Extension Tube, Fits M4/AR-15 Stocks, 7 Position, Black	RE-A5
Upper Receiver	Upper	Aero Precision	Aero Precision, M5 Assembled Upper, For AR10, Anodized, Black	APAR308503AC
BCG	Upper	Ballistic Advantage	.308 COMPLETE BOLT CARRIER GROUP, PHOSPHATE	BAPA100058
Charging Handle	Upper	Radian	Radian Weapons, Raptor SD Ambidextrous Charging Handle, Ported, Black, 7.62MM	817093020507`
Barrel	Upper	Faxon	Faxon Duty Series Barrel LR-308 8.6 Blackout 12" Big Gunner Contour Pistol Length Gas Port 1 in 3" Twist M18x1.5 RH Thread Tapered Shoulder with Adapter Nitride	10A863P12NGQ
Gas Block - Adjustable	Upper	Odin Works	Odin Works, Adjustable Low Profile Gas Block, Fits .875" Diameter Barrels, Nitride Finish, Black	GB-ADJ-.875
Handguard	Upper	Wilson Combat	HANDGUARD, AR-10, M-LOK, 10.6", BLACK ANODIZE	TR-MLOK-AR10-10

 

Need to find a muzzle device of some sort - and hopefully pick up a pistol length gas tube locally as I forgot that when putting together the other orders (was waiting until I chose a barrel - and that happened late).    

 

[BigNate]

Also... I'm a dummy and had assumed that the pins and levers in the AR10 lower were interchangeable with AR15 parts...  Lesson learned.   Went looking for the parts kit from Aero and they were mostly out of stock.   Found a generic set of parts from S2 Armament in North Phoenix.  Also grabbed a pistol length gas tube there.  I think I'm complete other than the muzzle device.  Parts started arriving last night and tracking tells me that I MIGHT be able to get it together this weekend.   Fingers crossed. 

 

[98Z5V]

I'm giggling with excitement...  

[dpete]

On 12/12/2023 at 1:21 PM, BigNate said:

I went looking for available commercial ammo and found some.  It's not cheap - but I will be buying at least a box or two of factory loads for "break in" of the rifle.  Well  - not so much to actually break in the rifle - but to take load workup variables out of play for the first few rounds through the gun... 

 

Anyway - stumbled on these - which immediately led to "I've got to source a block of ballistic gel..."  🙂

 

350 gr Supersonic

 

I thought those bullets looked familiar.

From the description:

Caliber: 8.6 Blackout

Bullet Weight: 350 grains

Bullet Type: SOLID COPPER Maker SUBSONIC

Casing: Brass / New

Muzzle Velocity: 1060 FPS 12” Barrel Suppressed

Muzzle Energy: 874.61 ft/lbs

Number of Rounds: 20

 

The 200 grain Makers are what I use in my 300 BLK subsonic hunting rounds.  They do petal open like that and at 50 yards will touch holes with my hand loads.  I've probably taken half a dozen deer with them.    I run mine 970-980 fps.

[BigNate]

19 hours ago, 98Z5V said:

I'm giggling with excitement...  

LOL…

[BigNate]

OK - started the build... ran into a couple of issues...

1) All parts arrived except the buffer tube.  Called Vltor - sounds like a carrier pickup issue - I should have it by Wednesday.

2) The lower parts kit has most of what I need but there are a couple of aero specific items that are missing.  I'm sourcing today.

3) Need to source a vice block or barrel installation tool for the AR10 platform. If I can't bum one in the next day or two I'll order one. 

4) Ordered 40 rounds of Gorilla ammo - 20 subsonic 20 supersonic 

Hoping to put rounds through it this weekend. 

[98Z5V]

  GIT 'EM, BUDDY!!!

[98Z5V]

11 hours ago, BigNate said:

3) Need to source a vice block or barrel installation tool for the AR10 platform. If I can't bum one in the next day or two I'll order one. 

If you wanna drive, you can hit up my Gun Pusher down here.  I leave my large frame Geissele Reaction Rod at his shop.  He uses it more than I do.  You can always just show up at his shop and say, "Tom said you would use his reaction rod to install  this barrel for me, as payment for him loaning you his tools..."  

The first thing he'll say back is, "Aaaaah, that motherfucker...  Gimme the parts..."  

[BigNate]

35 minutes ago, 98Z5V said:

If you wanna drive, you can hit up my Gun Pusher down here.  I leave my large frame Geissele Reaction Rod at his shop.  He uses it more than I do.  You can always just show up at his shop and say, "Tom said you would use his reaction rod to install  this barrel for me, as payment for him loaning you his tools..."  

The first thing he'll say back is, "Aaaaah, that motherfucker...  Gimme the parts..."  

That’s tempting… 🙂

 

I picked up one of these….  https://guntecusa.com/product/dual-ar-5-56-308-cal-upper-receiver-aluminum-vise-block/  It fits up nice.   I looked at those Geissele Reaction Rods - nice stuff - but I’ll buy one of those when I think I’m going to go into business building AR-10s…  Until then - I’ll use the $40 vice block… of drive down and abuse your gun guy… 

Ordered a little jar of Nickel/Graphite anti seize (good to 2600 degrees) after reading a bunch of folks basically saying “use whatever grease you’ve got - hell - just spit on it our use axle grease” but a few suggesting the high temp nickel based stuff….  

Also ordered a baggie of #4-40 X 1/8” set screws which is what Aero says plugs the hole for the detent on the rear receiver pin - they’ll be here tomorrow. 

Ordered a 1 3/16th crow foot wrench for the Wilson Combat barrel nut - it’ll be here tomorrow as well.   Have a torque wrench, a bench vice, and some delrin vice blocks to hold the guntech block - hoping that’ll be good.   

Brushed, patched and then stuck a borescope down the barrel a little fearful based on some of the bitching I heard about Faxon.  It looks ok to me.   Hopefully the upper and everything but the buffer tube asst on the lower will be together tomorrow night.

@98Z5V  Any position on grease vs oil.  I generally grease my older generation stuff (M1A, M1 Carbine, etc) using a decent gun specific grease - and oil my AR stuff - but stuff feels really pretty stiff.  At a minimum I’ll oil the piss out of everything - but I’m tempted to grease up the BCG, upper rails, etc. to have more there for the first shoot as stuff breaks in.  

 

Edited December 19, 2023 by BigNate

[98Z5V]

1 hour ago, BigNate said:

drive down and abuse your gun guy… 

He loves it, even when he's bitching about something...  

For oil, I use the stuff from @JBMatt, ever since it was concocted.  It's the best stuff on the planet.  You two don't live far apart - he might be able to get some to you.  When do you plan on shooting it?  This coming weekend?

[BigNate]

12 minutes ago, 98Z5V said:

He loves it, even when he's bitching about something...  

For oil, I use the stuff from @JBMatt, ever since it was concocted.  It's the best stuff on the planet.  You two don't live far apart - he might be able to get some to you.  When do you plan on shooting it?  This coming weekend?

Yes - hoping to have it out this weekend…  I’ll try to get with @JBMatt… 

 

Edited December 19, 2023 by BigNate