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Discussion Starter #1 (Edited)
I'm building a 6.8 upper and the last part I have to order is the gas block. Should I get an adjustable gas block if I plan to shoot hot loads (120gr SST with AA2200)? Of course it doesn't hurt to get an adjustable gas block to fine tune the rifle, but it is one more thing that can go wrong. I'm just wondering with max loads, is there a benefit like reducing recoil and would a fixed block be over gassed with hot loads. Wilson Combat just came out with an interesting adjustable gas block 2 days ago with a click adjustment screw, but a bit pricey at $120.
 

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A fixed gas block could be over gassed with some loads and under gassed with others. In my opinion a good click adjustable is always the best option. I haven't seen the Wilson Combat versions but I have had good luck with the SLR Sentry 7.
 

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Buy the adjustable gas block now so you don't have to take your rifle apart to change it later.(Please don't ask me how I know this...;) )Set it and forget it...it will be there if you need it later.

AzCasper
 

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A drop of CLP on the screw threads and run it in and out a couple of times every other barrel clean will keep the thread from locking up with carbon.
 
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Discussion Starter #5 (Edited)
A drop of CLP on the screw threads and run it in and out a couple of times every other barrel clean will keep the thread from locking up with carbon.
The new Wilson block has an auger cleaner on the screw which is supposed to keep it clean.
 

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I have done both. I used a 6.8 spc chamber for some years. In 2016, I jumped up to the SPC II chamber.

I am now building my new 6.8 Bison with an adjustable gas block. I am making it specific to one load. Once you adjust your gas block, keep that in mind. I have had mixed results when I tuned my gas block for factory Hornady 120 SST ammo. It is on the border of just enough to function well in the SPC II chamber.

If you tune for hot ammo, then anything with lower pressure is likely to cycle poorly if its cycles at all. My thought is go for it and enjoy the experiment!

TC
 

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I saw where Aero Precision has a new adjustable gas block. It is supposed to have a "sacrificial chamber" that lets some of the carbon collect there harmlessly. It doesn't prevent carbon from forming elsewhere, but slows it down where it matters. $64.00 was the price I saw; I'm thinking of getting one.
 

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A fixed gas block could be over gassed with some loads and under gassed with others. In my opinion a good click adjustable is always the best option. I haven't seen the Wilson Combat versions but I have had good luck with the SLR Sentry 7.
I'm struck, how can a fixed gasblock be over or under gassed? I always thought the gas port in the barrel determined such things.
I built my 6.8, albeit my first, with a Geissele Super Gasblock but did wrestle with this very question. I've built 11 ARs so far and have never used an adj GB. I did have to use the services of Clint @BRT once, problem solved.
 

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I'm struck, how can a fixed gasblock be over or under gassed? I always thought the gas port in the barrel determined such things.
I built my 6.8, albeit my first, with a Geissele Super Gasblock but did wrestle with this very question. I've built 11 ARs so far and have never used an adj GB. I did have to use the services of Clint @BRT once, problem solved.
The size of the gas port in relation to the amount of pressure created by a particular round is what determines such things. If you have a particularly anemic load and the gas port is opened up enough to cycle the lower pressure ammo then it would likely be over gassed with a higher pressure load. Everything is give or take. Lower pressure means you need a larger port, higher pressure means smaller port. AGB problem solved.
 

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I'm struck, how can a fixed gasblock be over or under gassed? I always thought the gas port in the barrel determined such things.
I built my 6.8, albeit my first, with a Geissele Super Gasblock but did wrestle with this very question. I've built 11 ARs so far and have never used an adj GB. I did have to use the services of Clint @BRT once, problem solved.
I also have never needed an adjustable gas block BUT only because the barrels I have are ported just right for the loads I shoot . If someone has a barrel that is ported on the small size or would like to shoot light loads the best option would be to drill a step bigger than needed and use a gas block .

Sent from my moto g(7) play using Tapatalk
 

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I'm building a 6.8 upper and the last part I have to order is the gas block. Should I get an adjustable gas block if I plan to shoot hot loads (120gr SST with AA2200)? Of course it doesn't hurt to get an adjustable gas block to fine tune the rifle, but it is one more thing that can go wrong. I'm just wondering with max loads, is there a benefit like reducing recoil and would a fixed block be over gassed with hot loads. Wilson Combat just came out with an interesting adjustable gas block 2 days ago with a click adjustment screw, but a bit pricey at $120.
Superlative Arms makes an interesting block that can be used in a "traditional" way or a "vented" way. The latter vents excess gas forward, out of the gas block, to minimize fouling. It's similar to how a piston AR gas block works. I've run win with about a hundred rounds through it and no problems so far
 

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I can see how the Wilson block self-cleans the port area but high pressure gas can still get up in the threads and carbon them up which is the ultimate problem that causes the adjustment screw to freeze up. I see no way to clean/lube the threads or even change the gas tube out.
 

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According to your comment, out of the gate, you are a reloader. Put the AGB on the new build and set it up for your loads. You can reduce or eliminate gas scraping on hot loads, which will eliminate little pieces of scraped brass in the BCG and or action. The AR gas gun craps where it eats, so try to clean up the residue as best you can.
 

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I have the Superlative Arms Gas Bleed Off adjustable gas block on at least ten of my 6.8 builds which is just a DI version of their piston drive block. Have the piston kit on four 6.8 builds to date and it's the only way to fly with short barrels and suppressors. Can dial it in for any load as has a wide range of adjustment.
 

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I like the Superlative block. I did run into a problem when using it on my ARP Creedmore. It would not bypass enough gas to work in that mode. I used it in the conventional mode and it worked fine. I guess it was not designed to work with some AR308 calibers.
 
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