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Discussion Starter · #1 · (Edited)
I always make a mistake with 6.8s. Lol.

My last one was short stroking (turned out to be remington ammo)

This one is a little different
Arp 16" Midlength barrel
RCA black nitride BCG, extractor spring has an insert
Vortex PST 1-4 scope
All other mega parts

First the good:
20 shot 50 yard group is like 1 messy hole
Ran flawlessly for 20 rounds of xm68gd
Locks back on last round even with federal AE

Now the bad
Stovepipes with Federal Ae 115gr even though the bolt locks back on last round.

Edit--- This gun has way more brass shavings at the 50 round mark than any owned.
Also, I notices that the bolt feels pretty tight into the carrier. Im not sure if that's a contributor or not.

Check out the feedramps, is it typical for them to not blend together perfectly? My other ARs do.











 

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Its ending up around 2 or 3:00 after bounding off the deflector. Does the picture take into the account that the deflector is changing the direction of the travel?
Yes
.... your ARP barrel is ported for using carbine buffer and spring so it might be more complicated

Is your gas block centered over the gas hole ?
Do you have any leakage at the gas block or tube?

What carrier profile are you using ? Semi auto or full auto?

Is the gas tube centered in the hole in the upper? Its hard to tell by your picture.

Have you modified the feed lips on your mags at all? How do the rounds present themselves at the top of the mag?

You might have multiple issues.

You could try tweaking your mag lips, radiusing the ejector pin, maybe blend your feed ramps, and with the rifle buffer/spring you might try a semi-auto profiled carrier if you have one.

Is your brass dull or scuffed up after shooting?
 

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I would definitely blend the feed ramps. You can use a chainsaw file or get the chainsaw sharpening stones for your dremel. This may be causing some of the shavings. Then I would remove and clean the ejector. Could be fouled with copper shavings. See what happens with that.
 

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Discussion Starter · #8 ·
Yes
.... your ARP barrel is ported for using carbine buffer and spring so it might be more complicated
This is probably going to be the fix. I have a mid length 5.56/rifle buffer combo that runs great and I just swapped the upper.

Is your gas block centered over the gas hole ?
Yes, the ARP barrel is dimpled so its in the right spot

Do you have any leakage at the gas block or tube?
Its tight, but the rail covers it. I suppose I can shoot it again with something around it to see if there is any carbon leakage

What carrier profile are you using ? Semi auto or full auto?
Full Auto

Is the gas tube centered in the hole in the upper? Its hard to tell by your picture.
Yes, the mega barrel nut is smooth so the tube can be straight through without any loading.

Have you modified the feed lips on your mags at all? How do the rounds present themselves at the top of the mag?
Negative. Ill Get a pic. I bought ASC mags, but the brass hit when pushed by hand so Im using PRI now

You might have multiple issues.

You could try tweaking your mag lips, radiusing the ejector pin, maybe blend your feed ramps, and with the rifle buffer/spring you might try a semi-auto profiled carrier if you have one.

I don't have one here, just FA

Is your brass dull or scuffed up after shooting?
Only on the back near where the extractor grabs
Thank you,
The answers are in bold. I hope this helps.
 

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I would clean it up and lube the bolt body, gas rings and cam pin then try with a clean gun. The 115 AE is pretty dirty stuff. Make sure your ejector is free and not sticking.

I would blend the feed ramps as well to prevent any possibility of the bullets catching.

Your extractor should have the buffer inside the spring but does it have the O-ring over the spring as well?

Cleaning it up may show a difference adding an o-ring over the extractor spring may fix it.


Sent from a final firing position, the crosshairs are on you!
 

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Discussion Starter · #10 ·
I would clean it up and lube the bolt body, gas rings and cam pin then try with a clean gun. The 115 AE is pretty dirty stuff. Make sure your ejector is free and not sticking.

I would blend the feed ramps as well to prevent any possibility of the bullets catching.

Your extractor should have the buffer inside the spring but does it have the O-ring over the spring as well?

Cleaning it up may show a difference adding an o-ring over the extractor spring may fix it.

Sent from a final firing position, the crosshairs are on you!
I noticed that it was pretty dirty, and the ejector did seem to stick but it moved after I put some pressure on it.

There is NO O-ring. Which direction does an o-ring change the ejection pattern?

I just took it all apart and cleaned it up. The bolt did feel really tight before, and it seems to have loosened up a bit. Im considering going back tomorrow and trying again.
 

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Recently had an issue similar to your 3rd pic down; leaving empty in chamber. Ejector was sticking (retracted). Disassembled the bolt, used a #35 bit to clean up the ejector bore, and is functioning fine.

I'm thinking, as Woodstock stated, it was fouled with brass shavings.....

Using Mega billet U/L with ARP barrel and bolt. Feed ramps are GTG.
 

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I noticed that it was pretty dirty, and the ejector did seem to stick but it moved after I put some pressure on it.

There is NO O-ring. Which direction does an o-ring change the ejection pattern?

I just took it all apart and cleaned it up. The bolt did feel really tight before, and it seems to have loosened up a bit. Im considering going back tomorrow and trying again.
The O-ring over the extractor spring gives the extractor a stiffer grip.
Sometimes a slightly weak spring can cause your issue. I noticed it appeared pretty dirty and your bolt was probably dry inside the carrier. The dry carbon and new stiff parts can cause ill affect as well as crappy ammo.
 

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I would remove and clean the ejector. Could be fouled with copper shavings. See what happens with that.
Swstock, your symptoms are what I had last year. When you said you had lots of shavings, it make me think yours is a repeat of my situation. I had lots of shavings from working 130 gr loads without an adjustable gas block so I was over gassed. The shavings were thin enough they had gone down inside the ejector hole and piled up in the spring restricting the ejector pins movement. The shavings had actually worn away the spring pin holding the ejector pin. Not the easiest part on the AR to replace.
 

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Discussion Starter · #14 ·
Hopefully this cleaning will do the trick.

Any advice for blending the feedramps? I already have a chainsaw blade sharpener for my dremel.

What happens with a lighter BCG? Does it simply quicken the action sending itself back further or harder? I would like to keep the rifle buffer because it works mint with the 5.56 upper.
 

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Discussion Starter · #15 · (Edited)
Swstock, your symptoms are what I had last year. When you said you had lots of shavings, it make me think yours is a repeat of my situation. I had lots of shavings from working 130 gr loads without an adjustable gas block so I was over gassed. The shavings were thin enough they had gone down inside the ejector hole and piled up in the spring restricting the ejector pins movement. The shavings had actually worn away the spring pin holding the ejector pin. Not the easiest part on the AR to replace.
So it's possible that small shavings are getting into to ejector hole and jamming it up?

I'll try to get it apart. Now yours was overgassed causing the shavings? I doubt, mine is overgassed. my shavings are probably from the feedramps.
 

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So it's possible that small shavings are getting into to ejector hole and jamming it up?

I'll try to get it apart. Now yours was overgassed causing the shavings? I doubt, mine is my shavings are probably from the feedramps.
The shavings along with the carbon will stick the ejector. That's why I said to make sure it's free. It will be stiff but not stuck. Woodstocks post is stating the same.
 

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my new builds mainly using arp 16 and 18" barrels also with rifle/A2 lowers, perform exactly what you are experiencing. It will break in after 100-200 shots. (same ammo too, fed 90 gd and AE 115 fmj, along with: 110 hornady, 115 GD, nosler 90)

I also,
lots of hand cycling
wet-sand/polish extractor
remove O-ring if needed, sometimes they add too much tension
clean chamber very well 1st and after some firing
 

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Discussion Starter · #18 ·
Thanks for the guidance everyone.

Here is where Im at. Everything is cleaned up, the ejector moves freely (but has almost a slight zipper feel) its not perfectly smooth.

I tried to clean up the feed ramps but didn't want to go to far. The lip is still there a little but its not as pronounced. I also put a few rounds into a mag and cycled the action slowly to see whats going on.

The round sits high enough that I think it was able to clear the sharp edge where the ramps met.

The brass IS being scratched as it gets pushed toward the front of the mags. Im not sure if that matters, I don't think I have a feed issue. I think I have a brass flake issue.

I think im going to head back to the range tomorrow to see if this helped at all.

 

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you might see how strong/stiff the extractor spring is. if it's week it will come off the rim too soon and cause issues as well. if you have an extra AR spring in a rifle that works you could take it with you and switch it out. AFTER you have tried all the other recommendations otherwise you may never know which fix was the cure.
 

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you might see how strong/stiff the extractor spring is. if it's week it will come off the rim too soon and cause issues as well. if you have an extra AR spring in a rifle that works you could take it with you and switch it out. AFTER you have tried all the other recommendations otherwise you may never know which fix was the cure.
^^^^this is why I asked if the O-ring was on the extractor spring. Adding an o-ring could solve it, if that's where the problem exists.

I have ran into a couple "new" bolts with weak extractor springs lately that caused the same issue. They were builds I did for other people.
 
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