6.8 SPC Forums banner

21 - 40 of 49 Posts

·
Registered
Joined
·
1,916 Posts
I have several 6.8’s a 20” for longer range target shooting out to 600yds, though some shoot them to 1000 with 130/140gr Berger’s. I also have a few 16” guns for hunting and a few friends have have killed hogs and deer out to 480yds with 12.5” guns.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #22
The track2 is actually 13.9" and with a P&W warcomp closed tine it's a bit over that magical 16" so law abiding people can own it without being extorted.
I most likely could have someone cut on down and thread it but the gasblock area is made so that a fsb is not an option, too short. I dont intend to use a standard FSB but rather the ARMS 41b folding unit, fantastic piece of kit, I currently have them in two builds and another waiting to be used, I just love the look and I do actually use them too.
I have a Geissele set that I'll use, picked them up during their last BF sale, what a mess that was. I think they were bombarded beyond expectations. And I want to use the same Centurion Arms C-4 mid cut-out rail but the new m-lok version, also a BF sale buy from CA. Monty built my personal Mk12 mod1 for me and he and Corrie are fantastic people deserved of my money and support hence my desire for the barrel being able to accept the ARMS 41 unit and the mil type finish would be mostly for aesthetics but it's a great weatherproof finish as well.
For whatever reason I have just never been drawn to LWRC at all. I think mainly it's due to their stuff all being way over priced and too I just think it's all ugly. Couple that with the fact that they choose to support a state like maryland with their business just disgusts me. I only live about 30 minutes from them and have never even visited. Maryland cant be affording them any special breaks they hate guns. I'd like to see them move somewhere where the respect is mutual. I think Benelli or HK has a place nearby too.
Well, like I said before, it's good to know I'm not a total outlier in my thinking. Perhaps we could back-and-forth it more. I'm sure I'll need some pointers at some point.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #23
I have several 6.8’s a 20” for longer range target shooting out to 600yds, though some shoot them to 1000 with 130/140gr Berger’s. I also have a few 16” guns for hunting and a few friends have have killed hogs and deer out to 480yds with 12.5” guns.
Wow! That's some shooting right there! Sort of confirms to me that the potential is definitely there.
 

·
Registered
Joined
·
346 Posts
My 16" 6.8s are for hunting, I built another to mount an IR scope on for night hunting. my 12.5" is from home defense and my pistol 6.8 is my truck gun.
 

·
Registered
Joined
·
3,867 Posts
Just the usual, hunting, problem critter killing.

Mini 6.8 is great and not "ASSAULT MACHINEGUNNY OF DEATH AND DOOMY!" looking for around problem critters when whiners normally stop seeing it and call "LAW OFFICERS!". My ARP that is "ASSAULT MACHINEGUNNY OF DEATH AND DOOMY!" looking one is also great for problem critters and telling whiners who the "LAW OFFICERS" come out then whine when they get arrested for trespassing.
 

·
Registered
Joined
·
1,916 Posts
Wow! That's some shooting right there! Sort of confirms to me that the potential is definitely there.
There are better rounds for longrange shooting in an AR15 (224V, Tac6, ARP Predator line and the new 6mm ARC etc) but its capable and with the bergers its right there with the 6.5G at distance, and smokes it up close.
 

·
Registered
Joined
·
206 Posts
My 6.8 rifle has primarily been a hunting rifle. It has been extremely reliable, so I would not hesitate to use it for defensive purposes but as a hunting rifle it is set up with way more scope than is practical for HD distances.

Now I have two rifles, so one may become a dedicated HD rifle with a red dot.

If I go to a rifle training class I’d take a 5.56 rifle so I could use cheap steel case or Wolf Gold ammo. I can’t imagine leaving a couple hundred rounds of 6.8 brass lying on the deck.
 

·
Registered
Joined
·
287 Posts
I mostly range shoot my 6.8. I use federal AE 90 grains for cost (bout .33 a round though im about to start reloading). Havent pushed it past 200 yards. The only long range here is an hour away and $15 for access. For personal defense, I would say the Banshee in 10mm I have will do the trick for most situations.
 

·
Registered
Joined
·
41 Posts
I know the 6.8 ammo is more costly than say 5.56 and mags too but has anybody here built a 6.8 with actually training with it or does everybody use theirs for hunting and bench type shooting? I've yet to see a thread indicating the former.
My plan is to use it to train just like I do with my 5.56 guns. Once I get it tuned and I know it's right, work up a load that gets me combat accuracy or better hopefully, that I can then reproduce in mass, round up the mags for a decent load out and sight it in to my liking I plan to rotate between my 5.56 and this.
I'm hoping the Barnes 110gr tax, 90gr gold dot that I've bought a boatload of will result in an effective combat load. I've bought powders aplenty to experiment with and a bunch of FMJ for training.
What about everyone else, hunting, recreation or serious work.
Mine is a dedicated fighting gun. I do not hunt with it, I do not target shoot with it. It's sole purpose to literally destroy any person who has it in their mind to harm my family or myself. I suggest you look into Hornady American Gunner 6.8 loads. 110gr BTHP with the cannelure. ARP barrels love that bullet. It is their general purpose OTM / HP and based on testing I've seen works reasonably well for a variety of uses. It's also one of the cheapest 6.8 factory loads around currently at $.60 a round.

Here is with what my build has:
ARP 16" Scout profile 3R 1:11 barrel with gas port drilled out to 7/64th to work with faster burning powders that produce low port pressure (aka what most people call "weak ammo")
ARP 6.8 Bolt (their standard one)
Adams Arms Piston Optimized Upper Receiver
Adams Arms Mid-length free float short stroke piston with their P-Series micro adjustable gas block
Adams Arms NiB Low Mass one piece carrier
JL Billet NANO Magnesium/Aluminum Hanguard (just 4.2 oz for a 15", even lighter weight than carbon fiber!)
JP SCS buffer set up for 3oz weight and 80% black buffer spring
Precision Armament Hypertap 6.5 Creedmoor brake (don't like compensators, but love a really good brake, this brake has a very generous bore clearance of 0.060", even with 6.8 you still have more than 0.04" bore clearance, so no worries about baffle strikes)
Geissle SSA trigger
BCM pistol grip
BCM angled short VFG (I prefer the thumb break grip with some bend in my arm to balance endurance vs. natual pointing / recoil managment)
BCM / VLTOR mid-sized (I forget, I think it's their MOD2) 7075 charging handle
EOTech XPS3 holographic sight (2017 build date, so post "temperature drift scandal", testing has shown thermal drift is now comparable or better than the Aimpoint T2's one of which I previously had)
Riton Optics 3x magnifier
Aimpoint Twist mount base with Aimpoint Twist Flip mount for the magnifier (does both, you can flip to side, and twist if off to quick removal / swap of another accessory optic)
Magpul CTR butt stock with the 0.75" butt pad
Magpul MS4 sling
Magpul BAD Lever (since I run a flared magwell, this works better than trying to reach my thumb up over the flared magwell)
Magpul MBUS Pro back iron sights, they have absolute co-witness with the EOTech
Lancer Tactical flared magwell
SureFire X400 Vampire (does white lite, IR Light and IR Pointer for my L3 Gen 8 White Phospor NV)
SureFire two button pressure pad banded and zip tied to the hand guard (doesn't have pic rail on top and you can't use the M-lock top slots with the piston setup since the piston takes up too much room under the middle of the handguard, a bit ghetto but it works and doesn't move)
BA ambi selector switch (our instructor requires us to engage the safety during certain drills where we transition from rifle to pistol or during certain shooting games, so this allows me to use my thumb to go hot like normal but sweep with my middle finger to go back to safe)

Total round count is about 1,500 rounds in the past 6 mo. Shooting off the magazine prone with just the EOTech (not using the magnifier), I can achieve about 1 to 1.5 MOA using cheap Prvi Partizan 115gr HPBT (did some precision shooting when tuning the action and sighting it in to gauge what it can do). With the magnifier and Hornady 110gr American Gunner, also just shooting off the magazine prone, I can do 1 to 3/4 MOA consistently. So it's accurate.

I bedded the barrel but did not lap (the AA receivers were pretty square so didn't bother). When bedding I used a hybrid method, I used Rocksett engineering adhesive on the barrel extension then wrapped it with a 0.001" brass shim stock I got at my local hardware store. Barrel extension ARP used measured exactly 1.000" on my certified micrometer, but the AA receiver was 1.002 to 1.003. Fit was snug after shimming (had to use some force to get it into the receiver, but no heat). The rocksett would take up and non-uniformity the shim cannot, since the rocksett is only between the shim and the extension, I can still take it apart if I ever needed to. Brass shim stock is still durable enough for shim work down to 0.001" unlike aluminum. Stainless would work too.
 

·
Registered
Joined
·
41 Posts
60769


60770


The AA free floating piston is nearly identical in design to the LWRC piston design, in fact they were competing at the Army's trials back in 2016 for a possible replacement for the DI issue AR's. They found that on average the piston driven AR's ranged from 16% to 20% more reliable than the DI AR's, but that wasn't enough of an improvement to justify the cost of replacement, so it was ultimately rejected until recently when they decided to officially start trials for a new 6.8 caliber intermediate cartridge. While they are not officially adopting 6.8 SPC, the 6.8 SPC project proved the performance of an intermediate caliber / cartridge in an AR-15 sized platform. Hence why the US Army has officially started their 27 month long field trials for both new 6.8 caliber rifles and squad automatics (Sig seems to be the strongest contender from what I've seen).

The only major difference between the LWRC and the AA short stroke free floating pistons are that the AA piston is not vented (what they call gas regulated) where LWRC vents their piston (similar to an AK gas tube, once the piston passes a certain stroke length, any further gas pressure is vented). The AA piston remains pressurized until the bullet exits the barrel (theoretically achieving the best muzzle velocity of any semi-auto, but their primary reason was to avoid visible flash from the gas system for night vision compatibility which the US Army wanted). It is self cleaning, I had a AA piston 5.45 build, shot 4,500 rounds of DIRTY Russian 7N6 from the 80s without ever cleaning the piston or BCG, not a hickup.

What I like is that you can buy the individual parts, the drive rod / piston cup, the gas block, both fixed and adjustable, their piston optimized uppers and their one piece forged carriers in standard weight or low mass, nitrided or NiB. There are lots of options. They also make one piece DI carriers as well that improve reliability of DI setups. I think the only caliber they said would not run with their piston system was .300 blackout which could care less about. 5.56, 5.45, small frame .308's, 6.8 SPC, 6.5 Grendel, any wild cat based off the above etc. Also just use a standard DI bolt, just pop off the gas rings as they are not needed.

My only gripe is hand guard choices. You NEED to use a steel barrel nut. Aluminum barrel nuts are not strong enough to handle the force of the pressurized drive rod / piston and it will shear the edge of the aluminum barrel nut. I tried an aluminum nut for the JL Billet hand guard, but it sheared off the lip in 30 rounds. So i used a steel barrel nut from Brothers and Arms designed for the AA piston setup with the JL Billet hand guard and modified it for a stronger mounting system than just friction clamp.

AA makes their won P-series M-lock hand guards in 15", 12" and 10", their weight is comparable to most 6060 hand-guards on the market, but I wanted to go as lightweight as possible hence my hybrid creation using JL's magnesium aluminum NANO hand gaurd adapted to the BA steel barrel nut.
 

·
Registered
Joined
·
41 Posts
Note that I did drill out the ARP barrel's gas port to 7/64th's got get it to run reliably with the AA piston. Standard DI, AA, LWRC or what ever other system etc. they are all slightly different in how much gas flow is needed to drive the system based on diameter and also if you need a little bit of over-gassing to cycle the action when the rifle is NOT shouldered, such as bringing the butt stock up over your shoulder for founding a corner inside a building, a common technique for using longer guns in tight spaces.

Also the load, heavy and slow or fast and light, what is the powder burn rate (some powders generate most of their pressure within the first few inches, others burn slower, so the pressure peak is lower, but remains higher for longer, those powders will generate more port pressure to drive the action). These are all factors to consider. But I can say the recoil impulse is phenomenal with this setup. I have mitigated the recoil impulse as much as possible save for developing a balanced action like in the AK-107. It literally feels like a .22 bolt gun! Again, my goals are different than others though. I aim to achieve maximum concentration and volume of accurate fire.

While 6.8 is a great cartridge and has some significant advantages in performance over 5.56x45 / 5.45x39 / 7.62x39 especially through intermediate barriers like auto glass, dry wall, AK mags etc., projectiles can fail to expand, miss vital organs, drop below hydro-static shock velocities...you name it. Being able to place multiple shots in rapid succession and in close proximity (group size) is very beneficial to stopping a determined adversary or multiple determined adversaries.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #34
Sounds like you put much thought into your build, congrats. And it seems our philosophy on the 6.8/purpose of our builds are tracking parallel to each other. Great looking rifle by the by.
I have bought a 200rd crate of the Hornady AG 110gr stuff you suggest, it came Monday so I may be heading to the range this weekend for a brief trial run. We are also trying to prepare for a move coming up June 6th (sucks big time) so not positive I'll make it or not. OR.......
I broke down a 5.56 build a few nights ago that I only put 3 whole mags through and I forgot that I used one of my BCM uppers for that one so I now have a fired-up upper that has a receiver ext bore of .998", I had to drive that Noveske barrel in and out, it's been squared too already so I'm thinking I may re-build my 6.8 using it, and the Centurion Arms C-4 from another previous build. I also now have a brand new Noveske Afghan barrel that has no purpose (oh no, here I go again). Maybe I'll sell it.
It's good to hear that that H AG 110gr load is generally well liked by ARP barrels. And about the ARP barrels and the gas ports, I'm unaccustomed to hearing gp sizes expressed as fractions, I always use the pin gauge or decimal descriptors like .076" or .78" and am unsure of 7/64" and what that translates to. This is one aspect of the 6.8 I desperately need to educate myself on, what are appropriate gp sizes, size ranges for given barrel and gas system lengths. As we all know the gas system is usually right at the heart of many problems with GAS guns.
I've never saw the need for brakes or comps on a 5.56 gun and tend to stick with good flash hiders instead, being unfamiliar with the recoil impulse of the 6.8 round I may need to reevaluate these as I too want to be able to gift my intended target with rapid multiple hits in quick succession. It's a big learning curve for me as I have been wholly immersed in the 5.56 world for many, many years and never imagined myself venturing outward anywhere else, surprise. So, I'm not aware of what's out there though I suspect that many of the brands/companies I've been dealing with for so long have 30cal muzzel devices. The piston systems you have though I know absolutely nothing about.
 

·
Registered
Joined
·
41 Posts
Myself and quite a few others on various forums I scoured before settling on the ARP 3R barrel noted that they had to enlarge the gas port. If you want it in thousandths, just divide 7 by 64 with a calculator to get the decimal, which gives us 0.109 in or 109 thousandths. I've seen others need to drill out to the 0.099" range as well for some of the commercial loads to run reliably, but it all depends on the gas system (some need just a tad more pressure like the AA does), buffer / BCG weight and buffer spring combination along with the load (what port pressure it produces) and your uses. Then also the friction of the upper, some are tighter than others, different coatings etc. all factor in.

As Constructor noted, 4 o'clock ejection angle of the brass is ok for a hunting / bench rifle, but for a fighting gun, you want 3 o'clock. Armalite tech notes say between 1 o'clock and 3 o'clock for optimal reliability, but Constructor pointed out that ejection in the 1-2 o'clock range will decrease accuracy. I say it will also likely decrease service life of the cam pin and buffer spring as well from my observations of over-gassed carbines and risk breakage. Cam pins do wear and can snap in AR's (DI or Piston) that are heavily gassed, although I've never broken one myself.

I tuned mine to eject between 2:30 and 3 o'clock on a hot day with a hot barrel so it has a little bit more headroom in cold weather (yah I shoot it when it's 20F outside just as I do when it 90F) on Prvi Partizan 115gr BTHP and Hornady 110gr AG BTHP (aka OTM) which seem to be darn close in the port pressures they both produce, but the Hornady is more accurate notably and slightly more consistent ejection. 110gr Hornady AG has now become my standard train / general purpose go to load if I run out of the Wilson Combat 95gr TTSX or 110gr TSX I use for my actual defensive loads. It will expands / fragments well out to 300 up to 400 yards, is accuracy, consistent and it's literally one of the cheapest 6.8 factory loads out there at $0.60 a round.

I do believe the 110gr BTHP projectile with cannelure is the same 110gr OTM projectile that the US military tested during the development of 6.8 SPC combat loads running 2600 to 2700 fps. I just got a chronograph (haven't used it yet), so I have not chrono'd it in my ARP 16" 3R barrel, but I did find some reviews on 110gr AG stating they were getting 2600fps flat from a 18" barrel (didn't say who made it). But if it was a 4-grove, my 16" 3R should hit a little higher than that even. All of my loads at least meet Constructor's recommended minimum of 2500 fps from a 110 to 115gr for combat loads. Eventually I'd like to get into hand loading and work up some to run in the 2650 to 2700 fps range.
 

·
Registered
Joined
·
41 Posts
Most of Hornady's 6.8 loads are speced with 16" barrels even though most of their other loads are speced in a standard 24" barrel (like their 6.5 Grendel loads which are from 24" barrels). But the 110gr AG didn't specifically say 16" barrel on their data sheet like it did for their 120gr SST or 110gr VMAX, so I was little concerned it would be a very weak round at just 2370 fps from a 16" until I saw that review from a customer running an 18" barrel and getting 2600, which is right in line with their spec and the same velocity as their 110gr VMAX that is specifically listed for 16" barrel length spec. in a week I should get a chance to go out again and now I have a chrono, so I can actually do a few strings to see what I'm getting with 110gr AG from my ARP 16" 3R. I got the 3R specifically to maximize velocity and extend fragmentation range without going to a longer barrel since they run 60 to 100 fps faster than a 4-grove stainless in the same length.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #37
What do you think of my use of the Vltor A5 setup? Any issues you can foresee? Again, I'm coming from a very long affair with the 5.56 where the A5 setup is tits. I have it on almost every carbine I use and it's perfect, on a 5.56.
 

·
Registered
Joined
·
52 Posts
I have built three 6.8s and did not like any of them compared to my Grendel. The ARP barrel does good to shoot 1” with 90s so I am going to order a McGowen 8 twist with standard rifling and go back to heavy bullets. I just ordered two more lowers to build out to an even two dozen. Like tater chips once you start......
 

·
Registered
Joined
·
287 Posts
I have built three 6.8s and did not like any of them compared to my Grendel. The ARP barrel does good to shoot 1” with 90s so I am going to order a McGowen 8 twist with standard rifling and go back to heavy bullets. I just ordered two more lowers to build out to an even two dozen. Like tater chips once you start......
1" at what distance? I haven't had any issues with my 6.8 keeping 1" or better at the ranges I shoot with 90 grain factory loads. I have a bison 16" barrel.
 
21 - 40 of 49 Posts
Top