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Discussion Starter · #1 ·
I'm doing my first 6.8 build and have read a lot of advice on the weight but most of the builds are way beyond mine. I'm using Aero XL upper with a Aero lower. Planning on a Wilson Combat 16" barrel. I will not be running a can of any kind. I run a Geissele super 42 just wondering if I could use the same spring with an H2? I use the H1 in a 20" 556 and its awesome.
 

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Try it and find out. It’s easy enough to swap buffers and springs in and out. I usually start with a standard carbine spring and standard weight buffer, then go from there.
 

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Generally, a standard buffer and spring is what is suggested. Try what you want and if it works to your satisfaction, then all is good. Otherwise standard and standard.
 

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Each gun will be different depending on how much gas is available.
I start with a standard carbine spring and an H buffer and see what the ejection pattern is and adjust from there.
 

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Careful with the XL upper. I built one for my brother-in-law, the xl doesn’t have feed ramps because it’s designed for a much larger round. Function testing had some feeding issues, possibly mag issue in conjunction with the ramps. I dremeled some feed ramps in.
 

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I'm doing my first 6.8 build and have read a lot of advice on the weight but most of the builds are way beyond mine. I'm using Aero XL upper with a Aero lower. Planning on a Wilson Combat 16" barrel. I will not be running a can of any kind. I run a Geissele super 42 just wondering if I could use the same spring with an H2? I use the H1 in a 20" 556 and its awesome.
Just wanted to add do yourself a favor and Buy a ARP 6.8 Barrel if not in stock they are worth the wait.
 

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Discussion Starter · #9 ·
Generally, a standard buffer and spring is what is suggested. Try what you want and if it works to your satisfaction, then all is good. Otherwise standard and standard.
I think thats what I'm gonna do. I spoke with Geissele today and they said they have never tested it on anything other than 5.56
Just wanted to add do yourself a favor and Buy a ARP 6.8 Barrel if not in stock they are worth the wait.
ARP over Wilson Combat???
 

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Discussion Starter · #10 ·
Careful with the XL upper. I built one for my brother-in-law, the xl doesn’t have feed ramps because it’s designed for a much larger round. Function testing had some feeding issues, possibly mag issue in conjunction with the ramps. I dremeled some feed ramps in.
Never thought of that! The upper was bought with intent of doing a .50 Beaowulf and because I was able to get it for $35 then I decided to go a different way. I may pick up another upper now just fro GP.
 

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ARP over Wilson Combat???
[/QUOTE]
Yes 100% ARP best barrels for the 6.8. Nothing against Wilson but there is nothing special about their AR barrels. ARP barrels have 3R or 5R rifling and ARP's Chamber you will get more FPS out of the ARP and accuracy is fantastic my 18" ARP with factory Hornady 120gr SST's shoots .0500" 5 shot groups at 100 yards i have not played with reloading for it yet but i will for my 12.5" ARP barrel.
 

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ARP run perfect with standard buffer and springs with almost every load out there.

Sent from my LM-K920 using Tapatalk
 

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I've run both ARP 16" and Daniels Defense S2W 16". With factory ammunition there's no discernable difference in either accuracy or muzzle velocity. ARP's really shine with hand loading for hunting applications, but if your not handloading three's no benefit. For tactical applications that 6.8 SPC was originally designed for, Daniels is untouchable.

The S2W profile is a tapered heavy profile, so it's a bull barrel at the back where you get all the heat, but a standard barrel out front to minimize weight at the end of the rifle. The barrels are cold hammer forged at 50k PSI including the chamber (I posted a video on this from DD a while back as some suggested the chamber wasn't hammer forged, only the bore / rifling).

They use a modern electro plating process pioneered by Boeing for their chrome lining which is about 2.5x more durable than either Nitride or GI Spec chemical etching chrome lining, which is the long established industry standard. Criterion has some high end match grade barrels that are also chrome lined using this process and state their barrels will hold 1/2 MOA or better for 20k rounds or more.

So keep in mind there's two different methods of chrome plating, the old GI standard that is only slightly more durable than nitride (but slightly less accurate than nitride and higher friction) and the modern electro plating process which is quite a bit more complex but produces plating with NO mirco-cracks (which is what kills GI spec chrome lining sooner that it would otherwise) and extremely high uniformity with better lubricity than GI spec chrome lining.

These DD barrels shoot just as well as Wilson's and ARP with factory ammo in my testing. And as stated, every barrel, even from the same manufacturer has specific loads that will perform optimally and others that won't. So ARP is great for certain applications, but not as great for other applications. There is NO BEST BARREL. Only barrels that are optimal for a specific application.

Having used both an ARP 16" 1:11 3R Scout barrel and now using a Daniels Defense 16" 1:11 5R S2W profile, for my applications I prefer the incredible heat tolerance and ruggedness of the DD barrel and since I shoot all factory loaded ammunition at this point, there's no difference in muzzle velocity between the two. I've literally chrono graphed hundreds of rounds at this point of various loads, 110gr Hornady OTM, 110gr Hornady Black (VMax), 115gr Prvi Partisan, 95gr TTSX, 110gr TSX and recently 120gr MKZ loaded by DHA for CBB (which really likes longer barrels irrespective of chamber, rifling or plating process) and 110gr Nossler loaded by DHA.

Both the ARP and DD barrels are mid-length gas. So if your looking for hunting applications and hand loading, APR is the best choice. If your a high volume tactical shooter with maybe occasional hunting / plinking, I think the DD barrel will serve you better because it will hold accuracy much better when it gets hot being both cold hammer forged and a heavy profile as well as wear better (you will probably never shoot out this barrel no matter how hard you run it).

Remember also heat plays a big role into barrel wear and accuracy. So on average a heavier profile will run cooler and last longer simply because of the lower average heat. High rigidity of the heavier profile reduces whip as does the aligned lattice structure of the cold hammer forging process. These factors also play a role in accuracy and not just longevity / ruggedness.

APR 16" Scout Profile: Mid-length gas, 1:11 Twist, 3R Rifling, Nitrided 4150 CMV, ARP's proprietary chamber, 28.6oz

DD 16" S2W Profile: Mid-length gas, 1:11 Twist, 5R Rifling, Electro-Chrome Plated Cold Hammer Forged 4150 CMV, SPC II Chamber, 36.9oz
 

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Regarding buffer weight, I highly suggest running an adjustable gas block no matter what barrel you use. Recoil impulse is determined by energy, not mass or spring tension. Mass and spring tension are used to tune the carrier speed and shape the impulse wave form for a given amount of energy. More gas flow = more energy = the need for more mass (momentum) and spring energy storage capacity = more actual recoil. This is why all competition guns run low mass carrier setups, because they are running the very minimal amount of gas flow to cycle and the mass / spring energy storage capacity is tuned to match that, kind of like determining the weight of a flywheel on a car for a given application.

I've tested literally almost everything out there and have found I prefer the JP SCS buffer system the most of all buffer systems. I've used the AKTIVE buffer, regular H1 / H2 / H3 GI spec buffers and Hydraulic Buffers. I've tried GI buffer springs, Geissele 42 braided wire springs, Spring Co Springs and Tubbs flat wire springs in various combinations and none of them offered the tunability, smoothness or just right impulse of the SCS.

It's spendy, but a highly tunable system and much smoother than everything else I've tried without causing cycling issues. Paired with an adjustable gas block, you can really tune the impulse energy (minimize it) and feel (short and peaky or long and drawn out) for your application and still retain reliability.

The combination I've found to be preferable in terms of both reliability (feeding a fully loaded 25 round mag, cold weather on a dirty carrier) and impulse is to pair a low mass carrier @ 8.5oz (there's a bunch out there, pick your choice brand) with the SCS set to H2 (2 tungsten, 1 steel weight) and the 85% black buffer spring (comes with a pack of 5 tuning springs). Total mass between the carrier and buffer is 13.1oz vs. a typical carbine setup with standard carrier and 3oz carbine buffer @ 14oz.

With this combination I have a little less mass with more dead blow effect which can compensate for the slightly lower mass while eliminating spring resonance. Since the buffer weights are separated by o-rings, there's just a little bit of damping so it's not harsh at all, but not as drawn out as a hydraulic buffer or AKTIVE buffer. You get a very light and smooth recoil impulse but it feeds everything without issue. I ran this combination on my ARP Scout barreled upper for 1,500 rounds without cleaning.

Then due to the heat issues for my application, I switched over to a DD barreled upper which now has about 450 rounds without cleaning and is still cycling reliably (ARP was out of their SOCOM profile which got me looking into alternatives other than ARP).

Both uppers used adjustable gas blocks and were precision hand assembled (gas block sealed at the port and tube, receiver squared and barrel bedded on an interference fit receiver). Both uppers shoot between 3/4 to 1MOA with the same factory loads using a 6x Razor HD Gen II-E LVPO, I could probably squeeze more out of both with higher mag and hand loading, but given these uppers purpose I opted for versatility and ruggedness over absolute precision at any cost.

I would argue, does 1/2 MOA to 3/4 MOA make any meaningful difference? Probably not at the ranges this caliber is capable of being used. Even 1 MOA is plenty good enough for 500 yards or less and then we go back to other questions such as how consistent does it remain when it gets hot? will I shoot it enough to heat it up? Is my application more than just hunting? How much will I shoot over the lifetime of the rifle? How quickly does accuracy degrade as the barrel wears?

These are all things you must answer. Hope this helps, but I do agree that ARP is the best choice for hunting applications with hand loads, but I think for other applications I prefer the DD S2W hammer forged barrel.
 

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I've run both ARP 16" and Daniels Defense S2W 16". With factory ammunition there's no discernable difference in either accuracy or muzzle velocity. ARP's really shine with hand loading for hunting applications, but if your not handloading three's no benefit.
You must have an oddball barrel. No benefit from ARP ? how about velocity. I get over 100fps from what the box says one factory ammo i use is Hornady 120gr SST factory load , box says 2460 im getting 2567. Now my barrel is a 18" so half of that velocity is from the extra 2" of barrel. To say there is no benefit for factory ammo in a ARP is simply False.
 

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I’ve owned ARP, Wilson, Daniel Defense, and Bison barrels, and MY best performers have been ARP and Bison. To be fair, the DD was 5.56, but it wasn’t accurate enough to interest me, and neither was the Wilson 6.8. I still own ARP and Bison 6.8s. Premium price doesn’t always mean a premium barrel.
 

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You must have an oddball barrel. No benefit from ARP ? how about velocity. I get over 100fps from what the box says one factory ammo i use is Hornady 120gr SST factory load , box says 2460 im getting 2567. Now my barrel is a 18" so half of that velocity is from the extra 2" of barrel. To say there is no benefit for factory ammo in a ARP is simply False.
This has been my experience as well. I've chorno'd several types of factory ammo in a DD 16" S2W nitride barrel and an ARP 16" barrel and, without exception, all loads shot about 100fps faster in the ARP barrel.

-Stooxie
 

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I would imagine if you were going to shoot heavy bullets loaded longer than mag well the spec2 would be a better choice than ARP but for what I shoot ARP is perfect

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