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Discussion Starter · #1 ·
This gun did just fine for the first 250rds, then the trouble began. When a round is fired the action seems fine. The empty is ejected about 20ft and a fresh round picked-up. When the bolt closes, though, it doesn't lock fully and pulling on the trigger gives no joy. If I cycle the action by hand it works fine, even if I do it very slowly. Today at the range I fired 20rds manually cycling. The unfired empties ejected easily except two that required banging the butt. I've tried different gas settings, removing and reinstalling the gas block, lubing the bolt and carrier, different mags and hotter ammo. Terra checked the bolt and pronounced it OK. I just installed the heavy hammer spring, and the problem may have gotten worse. Ideas?
 

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<_< ordinarily I would blame the carrier, but it fit fine in three of the shop rifles when I had it here. It wasn't punching primers when I had it here - it's not doing it with you, is it?

Your ejector is firmly bolted in? I even checked your extractor for springiness, no problem there. Whiskey Tango Foxtrot!?

Check the whole rifle thoroughly for any pieces of brass, k?
 

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Discussion Starter · #3 ·
I was just checking things out. I had the gas tube incorrectly installed, with the holes facing sideways. Not aligned with the rib on the gas block. Could that cause problems?
 

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How did you manage that? The block should fit into the notch on the tube...

but yes, that would definitely cause cycling problems.
 

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Discussion Starter · #5 ·
How did I manage that? Believe me, if anything can be misaligned, misinstalled, mishandled, misshapen or mismatched, I can do it. Anyway, it's correct now. Next range day should be Sunday, and I'll try again. If the problem continues maybe I'll send you my upper and you can see whether it's too proud to work with a pink lower? Fingers crossed.
 

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Maybe, if the gas tube was sideways, the barrel was installed/locked down 1-2/16" too far forward which would mean the bolt would have a hard time going into battery but could be pushed by the charging handle when manually cycling.
 

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Yeah, I don't have my rifle in front of me, but if I'm remembering correctly, I don't see how the barrel could be quite fully seated with the gas tube in there sideways.

Did this problem start sometime after you first took the barrel off and reinstalled it (I'm presuming you took the gas tube out and put it back in wrong, rather than it being an incorrect factory assembly)?
 

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Discussion Starter · #8 ·
I'd prefer to think that the factory screwed-up, not me. Regardless of what I'd prefer, I believe the problem didn't appear until I fooled with the disassembled gun some. Hopefully things will work properly, now. There's enough play, at least on my gun, to install the tube sideways.
 

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Once the gas tube and barrel are fully seated, you shouldn't be able to rotate the gas tube (more than the little bit of play the notch allows). It should be able to move fore and aft ever so slightly, but more than 1 or 2 degrees of rotation should not be possible. If it is, the barrel is not fully seated.
 

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Actually, fully seating the barel shouldn't affect headspace as this is managed by the Bolt/barrel locking.

But not fully seating the barrel is still a silly error.
 

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Mickey I respectfully disagree,If the barrel is not tight against the receiver the bolt cannot go forward enough to engage it's recesses fully.The bolt carrier/piston assembly only allows the bolt to go forward so far.This could be similar to firing out of battery depending on how much the bolt was from reaching it's fully seated position,or completely in battery.I cannot see how this is not excessive headspace,the cartridge is not fully chambered,and depending on how much the difference is,could cause anything from blown primers or broken extractors up to a catastrophic failure.



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If the bolt is far enough forward that the bolt can't close, no issue other than fitting the barrel properly.
If the bolt can close but is loose enough to have a headspace issue then the bolt is too loose in the barrel lockup area and both and should go back.

The XCR does not headspace based on the barrel position relative to the reciever, it hedspaces relative to the bolt, same as an AR. This way the pressure of firing is held between the barrel and bolt and not the reciever.

Without seeing the case post firing or any carbon buildup in the chamber it's hard to work out if this is excessive headspace. the best solution would be to get it back to Terra so she can work out the issue and resolve it. It could be an out of spec barrel, bolt or someting else.
 

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Mickey, that definitely makes sense...

I still think the first thing I would do would be to get everything seated correctly and try it again, prior to sending any parts to the factory. I don't know how far forward the barrel can be before you start having problems locking up, but it definitely sounds like something that should be corrected prior to declaring a problem with the rifle.
 

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Headspace is an issue on rifles where the bolt locking lugs are in the reciever and not the barrel. Then barrel to reciever fit becomes critical.

The only reason an XCR should have an issue with headspace would be either the barrel is shot out, or either bolt or barrel are out of spec.

If the bolt can be forward enough to not lock in the chamber, but the hammer can still actuate the firing pin and thence the primer, the rifle has a design flaw. That would hoverer require the barrel to be so far forward that the locking bolt would not engage. I suspect the issue is gas escaping from an improperly fitted gas tube and not providing enought force to cycle the action correctly.
 

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I might be completely off base on this,but I fail to see how if the bolt travel is limited forward by the receiver that it can completely engage the receiving recesses in the barrel extention if the barrel isn't tight against the receiver.In other words,the bolt can go forward no farther,but the barrel isn't where it should be,say 1/4 away from the receiver,would there not be a resulting gap created by the bolt being as far forward as possible but the barrel not being back far enough where it should be.I can't see how the cartridge could possibly reach the chamber completely if the bolt can't reach it's intended stopping point.



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No worries here,I like the hell outa Mickey.We don't always agree,but that makes for any "interesting" discussion. >:DI just want to make sure someone doesn't have a KABOOM!!.If I'm wrong I'll admit it,I just need proof,now maybe I'm too stupid or stubborn to see it,but neither is intentional.Sometimes people "see" things with their mind's eye in different ways,which is a good thing,hence NEW ideas.Anyway no ill feelings here.



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No problem. Grab your bolt and barrel, oil the crap out of them and see how they fit and lock up together. Nothing kinky though!

It's the same with an AR barrel and bolt. Just use plenty of thin film oil as they can be a bit of a bugger to take apart.

Then you can play with it assembled, but use washers to hold the barrel further out from the reciever and see how far out it can be before the bolt carrier can not deliver the bolt to the barrel for lockup. It shouldn't be possible unless there is free throw built into the carrier. Remember the bolt lugs work on the barrel extension, and not the reciever.

If the firing pin can be struck by the hammer when the bolt is not fully in battery then there is a design issue that needs to be looked at.

That is the whole reason aluminum works for the recievers, because it doesn't have to withstand the pressure of firing. The barrel/bolt interface does it all, and therefore handles the headspace.

Maybe I'm not describing it properly.
 
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