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Discussion Starter #1
What would cause the ejector to rip off part of a case? If I could post a pic I would.... New build, new cases, leaves slight ejector marks on cases also... Doesn't do it everytime but enough to piss me off! Never had this happen before.. AA2200 only 27.5grs @2.3 2575fps New cases I might add with Barnes 110TTSX but did it also with Hornady 110 Match
 

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Discussion Starter #3 (Edited)
Sounds like your brass is sticking in your chamber ,what kind of barrel is it?
Brand new ARP, 70 rounds through it
 

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Go to H's web site he has directions on how to clean the chamber probley has some residue left over from the melonite treatment.
 

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ShannonGTO, is it SSA brass? ... break, break ... ARP has two different chambers now. Which one do you have, the smaller chamber? Does a sized case go into your chamber? Note: without a bullet, you can drop a steel rod down the bore and knock it out easily (no need to hammer). If these are not issues, then you may need to polish your chamber lightly to make sure its clean and check for machine tool marks. Otherwise, it sounds like you are over gassed and the bolt is opening while the chamber pressure is too high and still holding the case against the chamber wall.
 

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I am confused, are you taking about ejector or extractor marks?
The ejector might be created by extrusion that normally means high pressures or an ejector with sharp edges perhaps?
The extractor has two ways to put marks on the brass, one when it goes in if the ejector doesn't move freely or it has too much tension and the 2nd when
the brass is hard to extract due to stickiness or due to early extraction.

Could you post a pic? There is nothing like a pic to see what might be going on.
 

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Discussion Starter #7
I am confused, are you taking about ejector or extractor marks?
The ejector might be created by extrusion that normally means high pressures or an ejector with sharp edges perhaps?
The extractor has two ways to put marks on the brass, one when it goes in if the ejector doesn't move freely or it has too much tension and the 2nd when
the brass is hard to extract due to stickiness or due to early extraction.

Could you post a pic? There is nothing like a pic to see what might be going on.




Pm your number and I will text it... My phone pics are too big and won't allow it...
i know I'm not over gassed with 27.5 and 2.3OAL... Works fine in my other 6.8...
 

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You can actually text pics direct to your Photobucket account, go to your account for the dets.

Sounds to me like it is a sticker chamber, had a couple ARP barrels need this. Now I polish all my new builds no matter the maker.
 

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I needed the ideal finish is with the finest grit like emery cloth like 280 or 320 ruining longitudinally.
A chamber should never be polished to shine.
 

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Posted for ShannonGTO

 

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Got the note. Saw the pics here too. That brass is ruined.
What you have there is extractor pulling like an animal so you might have stuck cases or crazy early extraction or a combination of both.
According to the primers you don't seem to have pressure problems but we cannot see the flash holes yet to confirm there is nothing else shady going on. Did you measure the brass at the base?
Possible solutions will be to inspect the chamber and make sure it is free of machine marks, normally easy to take care of with a 320 emery cloth.
But might also need to check timing for the bolt opening. Over-gassed systems are not that unusual in M4 type carbine deals but don't see them too often in quality 6.8 barrels. This might be
corrected with an adjustable gas block.
 

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Discussion Starter #12
Ok guys.... There's NO WAY I can be over gassed at 27.5 right? Still getting ejector pin marks... Only 1 68 does it with same load... I buffed the chamber with a 20gauge cloth cleaner as the site said but it wasn't enough I'm guessing? Going to go get Emory cloth in a minute
 

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Can you chamber a round and then manually extract it?
 

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Discussion Starter #14
No difference in guns other than a low mass JP carrier which is the bad actor
 

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Discussion Starter #15

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Ok guys.... There's NO WAY I can be over gassed at 27.5 right? Still getting ejector pin marks... Only 1 68 does it with same load... I buffed the chamber with a 20gauge cloth cleaner as the site said but it wasn't enough I'm guessing? Going to go get Emory cloth in a minute
Over-gassing doesn't mean your load is hot. A mistake on the porting job can turn a normal load into a bolt torching round.
We are just guessing. Whatever it is the extractor is pulling hard on the brass. So assume nothing. What is the diameter at the base?
Primer is one thing but also look at the whole picture. I see the marks but I don't see the typical extrusions.
Cancel the gas totally if you can. If you don't have a gas block with cancel choice then see if you can slide the gas block 1/4 of an inch or
move it sideways if you have a clamp or even reverse it with the gas tube sticking forward so you Cancel the gas and then shoot the same load again.
That will give you an appreciation on how much force is needed to open a fired round by hand. It should start opening with your two fingers w/o
much force. Then you can consider or discard the case stuck assumption.
Where are you located? Perhaps someone with experience in ARs can take a look at your rig.
 

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Discussion Starter #17
Over-gassing doesn't mean your load is hot. A mistake on the porting job can turn a normal load into a bolt torching round.
Whatever it is the extractor is pulling hard on the brass. So assume nothing.
Where are you located? Perhaps someone with experience in ARs can take a look at your rig.




Lol I build them bro.... I have just never seen this.... Never had a problem... I have an adjustable but it won't fit with the quad.... This is a customers gun I'm doing a load work up on
 

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Discussion Starter #18
Ports mic the same on both barrels.... This is 4k$ gun.... IOR/VALDADA Scope on it that makes my Viper seem like a NC STAR
 

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Ports mic the same on both barrels.... This is 4k$ gun.... IOR/VALDADA Scope on it that makes my Viper seem like a NC STAR
Lets assume nothing as I said. What is the measure on that port? What is you gauge saying?
Everything happens for a reason so you need to go and debug and measure every single thing in a specific order.
I extended my answer above. read again above to see if you can take one shot with the cancelled block.
BTW just to make sure is this a DI or a short stroke piston?
 

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Shannon
In my 20"ARP barrel I am also running a JP LMOS carrier and buffer but I am using an adjustable gas block. With the full mass (Auto wieght) carrier installed I had to run the block almost wide open for proper function but with the low mass carrier installed it was over gased on the same setting. Considering it is a 20" barrel with much lower port pressure than a 16" barrel without the use of a tunable gas system you may in fact be over gas or creating a timing issue with the low mass carrier.

I respect the fact that you build these rifles as I do as well and consider myself pretty knowledgeable but I allways seem to learn something new.
Using the exact same brass as you are when I built my first 68 I had some issues when I did not resize the new brass or try it in the chamber before hand at minimum. It was a stainless barrel so not an issue of sticking due to residue from the melonite process.

My next build was with an ARP melonite treated barrel and I cleaned it I thought pretty well but apparently was being to gentle and the brass was sticking to the chamber and coming out looking frosted or smoked with some pressure signs. After another more thorough cleaning the issue went away.

One of the other questions asked was if you are running the DMR chamber or standard ARP chamber. The DMR chamber requires the use of small base dies or Hornady dies as it is a tighter tolerance match chamber.
 
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