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My range session today with my new 12.5" build revealed some problems. I was getting heavy extractor swipe and blown primers even with the gas cut back to the point where it wouldn't fully cycle and with a H3 buffer. This was also shooting suppressed.
Before I go and drop $60 on head space gauges, does anyone have a set I can borrow? I'll pay shipping both ways.
I'll post more details later when I get my book in front of me but I have to leave now to take my wife on a pistol shooting / dinner date. 
I did all the trouble shooting I could do at the range including trying 3 different bolts.
Anyone have any suggestions what else to look for?
Some info:
Sabre Defense 14.5 barrel shortened to 12.5
Micro MOA switchable gas block, I'll get the port sizes later.
FA carrier
H3 buffer
Bolts
1st - AA hard use bolt
2nd - bolt that came with my Satern
3rd - bolt that came with the Sabre barrel. Marked "6.5 II" on one side and "X" on the other
Got to run.......
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txgunner00 Wrote:My range session today with my new 12.5" build revealed some problems. I was getting heavy extractor swipe and blown primers even with the gas cut back to the point where it wouldn't fully cycle and with a H3 buffer. This was also shooting suppressed.
Before I go and drop $60 on head space gauges, does anyone have a set I can borrow? I'll pay shipping both ways.
I'll post more details later when I get my book in front of me but I have to leave now to take my wife on a pistol shooting / dinner date.
I did all the trouble shooting I could do at the range including trying 3 different bolts.
Anyone have any suggestions what else to look for?
Some info:
Sabre Defense 14.5 barrel shortened to 12.5
Micro MOA switchable gas block, I'll get the port sizes later.
FA carrier
H3 buffer
Bolts
1st - AA hard use bolt
2nd - bolt that came with my Satern
3rd - bolt that came with the Sabre barrel. Marked "6.5 II" on one side and "X" on the other
Got to run.......
PM me...I have gauges and we're not too far apart.
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07-13-2014, 01:37 AM
(This post was last modified: 07-13-2014, 01:41 AM by Variable.)
Dang Tex. That sucks! Nothing is leaping out at me right off. I'm scratching my head. Reading your combo, it should run like a champ.
You have a heavy buffer, a heavy carrier, gas turned down, and a .308 can (extra volume, and less back pressure can-wise)..... Your Sabre barrel should have a real Grendel chamber too. Early unlock with your combo shouldn't be an issue to my thinking.
Your gas port was set for a 14.5" barrel, but you chopped it back (less dwell), but then added a can (more dwell). The adjusted gas block should have cleaned up any difference. Something is definitely out of whack somewhere, but I can't picture it in my head yet.
Did you try it without the can on? Anything happen then?
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What ammo were you using, reloads, factory ? If your ammo is proven I would definitely look at your chamber. Short barrels in the DI gas system can sometimes create problems when suppressed. This is one of the few advantages of a gas piston over the DI. That said, I have a DI gas system with a BCM 11.5" 5.56 barrel that runs suppressed with complete reliability tuned with a Syrac adjustable gas block.
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I'm curious as to what your gas port size is.
Don't know about Sabre grendel barrels, but their 5.56 carbine barrels are well known for having huge gas ports
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Blown primers would sujestion this is a over pressure load causing the issue,
Punctuation is for the weak....
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07-13-2014, 04:49 PM
(This post was last modified: 07-13-2014, 07:16 PM by txgunner00.)
Variable Wrote:Dang Tex. That sucks! Nothing is leaping out at me right off. I'm scratching my head. Reading your combo, it should run like a champ.
You have a heavy buffer, a heavy carrier, gas turned down, and a .308 can (extra volume, and less back pressure can-wise)..... Your Sabre barrel should have a real Grendel chamber too. Early unlock with your combo shouldn't be an issue to my thinking.
Your gas port was set for a 14.5" barrel, but you chopped it back (less dwell), but then added a can (more dwell). The adjusted gas block should have cleaned up any difference. Something is definitely out of whack somewhere, but I can't picture it in my head yet.
Did you try it without the can on? Anything happen then?
I didn't this time. I actually didn't get to shoot it that much because after about the 5th shot the ejector plunger got stuck down. I spent quite a bit of time trying to get it freed up and turned out the cause was crescent shaped slivers of brass that were shaved from the case head.
Shooting it with gas turned down resulted in less swiping but still had a few primers pop out both with FF 7.62 brass and with Hornady brass.
All of these were mild hand loads that shoot fine in my Satern barrel. 26 grains of 8208 behind a 120 sierra SP, AK brass - 27.6 grains of 8208 behind a 123 SST, Hornady brass.
No firing pin cratering at all. Just ejector/ extractor swiping & blown primers.
Swapping the bolt to the 3rd one above helped with the swiping but I still had a blown primer with Hornady brass.
More info to follow.
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Measured the bolt face depths as best I could with my calipers.
Satern & AA bolt - avg. .134"
Bolt 3 - avg. .139"
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07-13-2014, 06:25 PM
(This post was last modified: 07-13-2014, 06:38 PM by txgunner00.)
Gas port in the barrel is between .070" & .079", closer to the low end. I'm guessing .072". The large port in the adjustable gas block appears to be the same size as the barrel. The small port in the gas block is between .048" & .053".
edit: just checked MicoMOA's site. It appears the plate I was using has .070" & .049" ports.
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I'm beginning to wonder if this barrel's chamber is out of spec. I have to seat 123 SST's back to 2.220" whereas I can seat them at mag length in my Satern (2.260").
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txgunner00 Wrote:I'm beginning to wonder if this barrel's chamber is out of spec. I have to seat 123 SST's back to 2.220" whereas I can seat them at mag length in my Satern (2.260"). This short would suggest that factory loads should get significant marks on the ogive near the next after running into battery and ejecting the unfired round.
If this happens or your bullet stays in the rifle, then your throat is indeed too tight or too short.
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That's what this is looking like. I hope it's not the case but I need to order some factory loads to test it.
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Yeah, that could be bad. To my knowledge (I have no real "insider" knowledge), Sabre always used the real Grendel chamber. If you have a defective chamber that's chrome plated, well, that could be a real pain in the keester...
Hopefully it's something else not caught yet, and it's something easily remediable.
I can offer this input--- Both my 10.5" and 14.5" barrels were made by Sabre, and they run like raped apes with Wolf 120 MPT, Hornady Amax, etc... My handloads were 120 Nosler BT's seated to 2.267" with some running as long as 2.269" and they chambered fine.
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If it is defective I'm probably SOL with this barrel.
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txgunner00 Wrote:If it is defective I'm probably SOL with this barrel.
Well, not necessarily. If it does prove to be short, then Mark @ PF may be able to salvage it with his patented SCS (short chamber stretcher). 
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Chrome
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07-15-2014, 04:44 AM
(This post was last modified: 07-15-2014, 04:48 AM by NugginFutz.)
Whups - missed that part. 
Were all of Sabre's chambers chromed?
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I thnk all of the Vanadium barrels were. They did make some stainless match barrels though.
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I remember someone having similar problems with a Sabre on the old board.
That would suck--- My Sabre barrel can be seated to 2.260"...
I'm not sure about ejector swipes but have you looked at the firing pin? If it has a burr on it that could be causing your piercing problem.
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