Holy Double Feeds...Help me diagnose the extraction/feeding

[NHPiper]

I have an AR10 with an adjustable gas block. Gas block is properly set to the 16" barrel and 147 FMJ ammo. Today I started getting these bizarre extraction/feed issues where the ejecting shell would spin 180' and then cause the feeding cartridge to get jammed into the feed ramps. It only seems to happen with my suppressor on and I have shot with it on a handful of times and never had an issue. Any ideas? I tried adjusting the gas block to set it to the ammo with the suppressor on, but I still had 1 or 2 more of these feeds.

 

[padom]

Did you turn gas off and open it up one click at a time firing rounds each time till it locked back on last round?

 

[NHPiper]

Yes, and then confirmed it with another 3 rounds.

 

[padom]

I typically fire 20rd string after the bolt locks back. Sometimes you'll get a few that don't feed and need to open the gas up 1 more click.

 

[NHPiper]

Do you think this is really a feeding issue though? I'm curious why the brass isn't extracting in the chamber. I could understand if more gas is needed.

 

[Gunfighter14e2]

W/O the can on how far an where does it throw the brass? If only 2-4 feet an your extractor uses springs that most likely is the issue. Change to the enhanced extractor an never look back.

 

[lash]

I had a broken extractor once that did that same thing. Then I changed it for an enhanced extractor.

 

[NHPiper]

Without the can on it throws brass 4-6 feet to the 2pm position. With the suppressor it actually seems to toss it less, which seems counter-intuitive for me, I thought that would increase gas pressure and cycle the bolt harder.

BCG is the Nickel Boron Toolcraft .308 from Monmouth Reloading.

 

[Bigjake83]

I had a broken extractor once that did that same thing. Then I changed it for an enhanced extractor.

+1

 

[kingzero]

I had a similar issue and what helped me was adding mass to the buffer. Everything worked fine without the suppressor, but got weak extraction and jambs with the suppressor. What I suspected was the additional pressure from the can was causing the bolt to extract the case prematurely, while it was still swolen in the chamber. All the rearward energy of the carrier/ bolt is expended from the friction of the expanded case against the chamber walls and doesn't allow proper cycling and ejection. I turned up the gas till it cycled, but my brass was beat to shit. I then added mass to my buffer to try and keep the bolt closed a little longer to let pressure subside and the case to shrink. It worked and my brass looked much better.

I have since switched to the heavy JP VMOS and SCS with the highest spring rate. Sometimes you need mass regulation as well as gas regulation when using a suppressor.

 

[NHPiper]

Good idea with the buffer. I have been thinking mine is too light.

What did everyone do to get or install an enhanced extractor? Mine is brand new so I am surprised it may not be working.

 

[padom]

Buy the enhanced extractor, disassemble your bolt to remove your existing extractor and installed the enhanced..

 

[NHPiper]

Are all enhanced extractors the same quality? Do you recommend any particular brand? I am not familiar with them.

 

[padom]

Are all enhanced extractors the same quality? Do you recommend any particular brand? I am not familiar with them.

JP Enterprises. Here you go

http://www.brownells.com/rifle-part...nced-extractor-sku452000168-69268-140892.aspx

 

[lash]

That's what I used.

 

[NHPiper]

Thanks guys. I picked up a heavy mass buffer. Have to order the extractor next week when the paycheck comes in.

 

[Yondering]

Without the can on it throws brass 4-6 feet to the 2pm position. With the suppressor it actually seems to toss it less, which seems counter-intuitive for me, I thought that would increase gas pressure and cycle the bolt harder.

BCG is the Nickel Boron Toolcraft .308 from Monmouth Reloading.

Ejection to 2:00 is generally overgassed, and that's without the suppressor. Turn the gas back down a bit until ejection is more to the rear behind the 3:00 line at least.

Also keep in mind the difference between 147gr mil-spec ball and commercial 308 ammo; if you're tuning for M80 ball it'll be overgassed for commercial 308.