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Discussion Starter · #1 ·
One problem I had during my last range trip was that the bolt seemed to get stuck in the rearward position on a couple of occasions. The only way that I found to release it was when I finally tried to separate the upper and lower receivers. It seems that pushing the button to release the upper receiver from the lower receiver will cause the bolt to be released from this rearward/stuck position. I was using a 6.8 conversion kit on my XCR and I have only about 200 rounds through my XCR (mostly 5.56, and ~50 6.8).

Has this happened to anyone else? Is this just too much gas pressure causing the bolt to get stuck in this rearward position?
 

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Not really sure what it is doing, has it only happened with the 6.8 or has the 5.56 done this? Can you tell what it is getting stuck on? What gas setting are you shooting on? Would it not release at all when you pulled back on the charging handle and pushed down on the bolt release? If not, that doesn't sound right at all.
 

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Discussion Starter · #4 ·
Not really sure what it is doing, has it only happened with the 6.8 or has the 5.56 done this? Can you tell what it is getting stuck on? What gas setting are you shooting on? Would it not release at all when you pulled back on the charging handle and pushed down on the bolt release? If not, that doesn't sound right at all.
It only happened with the 6.8, but I have not tried shooting 5.56 after these occurrences. I couldn't tell what was stuck, because the bolt would immediately be released when I depressed the button to unlock to upper from the lower. Racking the charging handle did not work and neither did the bolt release. I was shooting on gas setting 4. I only have ~200 rounds through the rifle and I was going to shoot another 100 on setting 4 to break in, before turning down to 2 and test firing.

I'll head to the range again in the next week or so, and see if I can replicate it with either the 6.8 or the 5.56.
 

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Discussion Starter · #6 ·
your bolt hold release isn't working?
no. that is the first thing i tried along with pulling back the charging handle. when i pushed down the bolt release it almost felt like it wasn't moving. that is, it felt like it was stuck in the depressed / down position. i haven't really inspected the rifle since returning from the range. any thoughts on what to check when i do?
 

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Take it apart and check the bolt release moves freely and that the ejector is tightly fastened to the reciever wall. Also check both protrusions to make sure they are not bent. check the bolt and carrier for any wear marks that should not be present. Check the recoil spring has tension and that there are no obstructions in the oprod.

If it is only happening a bit it is most likely the bolt release or ejector locking the bolt back.
 

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Discussion Starter · #9 ·
i took a very quick look at my rifle last night. the ejector was tightly fastened to the receiver wall. i noticed a small shiny area (i.e. had some slight wear) along the bottom front half, thus it is being rubbed by the bolt/carrier during cycling. is there supposed to be some wear, or should the ejector be adjusted so that there is no rubbing against the bolt/carrier? of note is that the wear seemed to be along the front half of the ejector, not the rear where one might expect it to be if it is holding the bolt/carrier from moving forward.

the bolt/carrier likewise has some slight wear where it rubs the ejector. i also noticed that the bottom side of the bolt/carrier has lots of brass rub marks where it cycles over the top round in the magazine. i assume that this is normal.

the recoil spring has tension and there are no obstructions in the oprod.

the bolt release seemed to function normally.

any thoughts? should i loosen the ejector and readjust so that there is no rubbing?

thank you. i can take a closer look this weekend if/when i finally decide to clean the rifle.
 

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Finish wear on the ejector and on the ejector groove on the bolt carrier are normal.Does the rifle "lock up" to the rear when you manually cycle it,or just when you fire it.Does the bolt release have spring tention? In other words,does it stay down until either the magazine follower or you manually engage it? when it "sticks" can you just push it forward or is it locked to the rear? Just making sure you know,but you can push in on the charging handle and use it like a forward assist.
 

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it could be the rifle isn't getting enough gas to fully cycle, too. It is still in break-in, and the problem, according to the OP, has only happened a few times.
 

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Discussion Starter · #12 ·
Finish wear on the ejector and on the ejector groove on the bolt carrier are normal.Does the rifle "lock up" to the rear when you manually cycle it,or just when you fire it.Does the bolt release have spring tention? In other words,does it stay down until either the magazine follower or you manually engage it? when it "sticks" can you just push it forward or is it locked to the rear? Just making sure you know,but you can push in on the charging handle and use it like a forward assist.
the bolt/carrier locked to the rear on three occasions on my last range trip, but otherwise functioned normally during to the ~100 rounds of fun. i assume that the bolt release has spring tension, b/c the rifle functioned normally, except for these 3 occurrences. i will play around with it when i clean.

when the bolt/carrier was stuck to the rear, the charging handle moved freely.
 

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Discussion Starter · #13 ·
it could be the rifle isn't getting enough gas to fully cycle, too. It is still in break-in, and the problem, according to the OP, has only happened a few times.
i guess i'm just going to have to go to the range and force myself to do a little bit of shooting this weekend. i'll update after my next range visit. thank you all. and, if it happens again, i'll take better notes.
 

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In order to use the charging handle as a forward assist, you need to push the knob in towards the bolt to engage the catch. Then you may be able to 'assist' the bolt forward instead of just sliding the handle assembly forward.
 

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Discussion Starter · #16 ·
In order to use the charging handle as a forward assist, you need to push the knob in towards the bolt to engage the catch. Then you may be able to 'assist' the bolt forward instead of just sliding the handle assembly forward.
I actually had forgotten about using the charging handle as a forward assist. [I know that I read about it multiple times, but I failed to remember.] Even DTOM's earlier post didn't cause me to remember. I will try this if it the bolt/carrier lock up again. Damn, that would have been the perfect time to test that function.
 

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Discussion Starter · #17 ·
Did you drop the magazine when this happened? One thing to try would be some different mags, if you have them available.
I actually don't recall for sure. But, I am guessing that that would have been one of the first things that I would have done, along with depressing the bolt release and racking the charging handle.

I will report after my next range visit.
 

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The only thing that the bolt/carrier could be sticking on is the ejector,if was somehow bent and causing it to hang.Or the bolt carrier or it's being held back by the bolt hold open.It's unlikely the ejector is bent,so I would guess it might be some thing wrong with the BHO.Did you hold up on it while your were cycling the bolt to the rear,if so you may have bent it somehow causing it not to drop back down all the way when you release it,causing the bolt to stay hung open.Easy way to check is rack the bolt with an empty magazine(don't touch the bolt release while doing it)Now drop the mag,and run the charging handle a few times...did it go back into battery?....if not you might have a bent bolt hold open rod.What leads me to this is that when it did stick you couldn't get it to release until you opened the upper,which would release the carrier from the bolt hold open.
 

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Discussion Starter · #19 ·
DTOM, interesting theory that makes sense. I'm pretty sure that I have been careful not to cycle the action while pushing up the bolt hold open. I've seen pictures and read about problems regarding that on this forum and that is something I have consciously avoided. That said, there being a problem with the bolt hold open makes sense, because the bolt/carrier would release when I just slightly separated the upper from the lower. I'll test my rifle as you suggest later today and I'm also headed to the range this weekend.

Thanks again for your help!
 

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Don't thank me yet,I could be wrong...lol ;D
 
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