I built an AR-15 chambered in 6 ARC. The 24 inch Ballistic Advantage barrel has a rifle-length gas system and adjustable gas block. I replaced a standard spring and buffer for a rifle-length buffer tube with an Armaspec captured buffer system (H2). I am having occasional failure-to-feed conditions. Has anyone had success with a particular captured spring system for 6 ARC?
Spring System for 6 ARC gas gun?
- Thread starter chromatica
- Start date
Are you sure it's a rifle length gas system and not +1 or +2"? A +2" is kind of the norm on a 24" barrel.
I use an A5 buffer set up on mine, so I can't suggest anything as far as captured set ups. I start heavy on the buffer and keep reducing weight until I get reliable hold open on the bolt.
Does your bolt lock back on the last round and what is the ejection pattern, 2, 3, 4 o"clock?
I use an A5 buffer set up on mine, so I can't suggest anything as far as captured set ups. I start heavy on the buffer and keep reducing weight until I get reliable hold open on the bolt.
Does your bolt lock back on the last round and what is the ejection pattern, 2, 3, 4 o"clock?
Fast14riot
Gold $$ Contributor
Part of why I hate the AR15 platform. I really push for everyone to tune their guns with standard gas and recoil systems. Get the gun to run first. Then if you have issues, try switching things out. If your chosen cartridge won't run in a standard AR15, it may not be best choice for an AR15.
So either you're under-gassed or overgassed for the recoil system at this point, which is it? Given that you have an AGB, I'm guessing that You've turned the gas down to where the rifle will lock back on an empty mag plus a little? Where's your ejection angle 1,2,3,4 o'clock? As the first commentor mentioned, the standard gas lengths for ARC are longer than
.223, in general rifle for 18", rifle +1 for 18"- 22", rifle +2 for anything longer, although I have a rifle +2 on a 21" that runs fine.
The whole reason for the 6 ARC design is for it to run in an AR-15.
Yep, it is rifle length. Barrel specs say so and I ordered a rifle length gas tube that fits perfectly.
I have read some other threads that say that a long dwell time is a good thing. My gas port is 13 inches from the front of the receiver. That leaves 10 3/4 inches for the bullet to hang around in the barrel (and deliver pressure to the gas system).
I ordered several spring systems with different weights for testing.
Fast14riot
Gold $$ Contributor
I should clarify. I have a love/hate relationship with the platform. The part I don't like is all the "upgraded" "improvement" and like parts that get bought and installed before the gun is even tested. I'm not new to using uncommon configurations in the platform, I have two 24" barreled 6.8spc ARs and when I built them everyone told me it won't work. Well with some tuning and load adjustment I not only have very smooth running guns, I have even turned down the AGB and use standard weight buffers on a regular rifle gas system. Properly built, tuned, broken in and adjusted loads for the system (correct powder for appropriate dwell time for gas system and barrel length) you should have no problems running a standard buffer and gas system. Once one understands the system and how many of the "upgraded" parts may be two sides of the same coin to "fix" problems, you'll find that Mr. Stoner was pretty smart with his design and its flexibility.
I have a range report:
I substituted an H buffer for the H2 buffer I was using. It is an Armaspec Stealth. I also purchased the official Armaspec spacer for a rifle length buffer tube to replace the homemade spacer I was using. I opened up the gas block to full throttel (20 clicks). When I got to the range, the system was cycling reliably. I turned the gas down to 16 clicks, and still had reliable and had the same results at 12 clicks. At 8 clicks, the rifle stopped cycling and failed to lock back on the last round. I turned the gas back to 12 clicks and everything was copacetic. I tried some milder rounds and they cycled reliably as well. The brass is ejecting at 4:00. I'd say the tuning effort was a big success. Thanks for all your input!
I substituted an H buffer for the H2 buffer I was using. It is an Armaspec Stealth. I also purchased the official Armaspec spacer for a rifle length buffer tube to replace the homemade spacer I was using. I opened up the gas block to full throttel (20 clicks). When I got to the range, the system was cycling reliably. I turned the gas down to 16 clicks, and still had reliable and had the same results at 12 clicks. At 8 clicks, the rifle stopped cycling and failed to lock back on the last round. I turned the gas back to 12 clicks and everything was copacetic. I tried some milder rounds and they cycled reliably as well. The brass is ejecting at 4:00. I'd say the tuning effort was a big success. Thanks for all your input!
Why did you screw with it? Was it not working?
searcher
Gold $$ Contributor
I have had so many issues with encapsulated buffer systems from various manufacturers - I quit using them altogether in all but one rifle. One common problem that I encountered with almost all of them was the tendency to slow down the cycle of the action - often prohibiting the bolt to move rearward enough to pick up a round off the magazine, resulting in a short stroke condition. This is encountered more when shooting light varmint bullets - but have had it happen a few times with heavier bullets as well. I tend to not want to use adjustable gas blocks for reliability and simplicity reasons - and if the buffer causes problems - there is little other solution than to replace it with yet another buffer or go back to exposed spring buffers (my preference). I like trying new stuff out and some of these "aids" are great - and some cause more problems than they are worth. The only reason I still have one on a particular rifle is because the rifle was tuned with it in place - and it shoots incredibly well with that particular buffer. When encountering a short stroke situation with a regular exposed spring buffer, one only need pop the old spring out and replace with a Wolff reduced recoil spring. 20-second fix.
I wrote a message to Armaspec and they told me that my H2 spring/mass was likely too heavy for 6 ARC. If I had a fixed gas block, they recommended a carbine (C) buffer. Because I already had an adjustable gas block, they recommended I try an H buffer with the gas block somewhere near the halfway position. When I was shopping for this, I found a screaming deal on a C, H, H2, and H3 of the Stealth model. With this order complete, I had a full set of tricks to try and tame the beast.
BTW, the Stealth systems includes two different telescopic springs and several sliding masses. It is very smooth and very quiet.
BTW, the Stealth systems includes two different telescopic springs and several sliding masses. It is very smooth and very quiet.
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