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Bolt fails to completely close


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I've had this 12 for well over a year now and it's always been very reliable until fairly recently. Much too often the bolt has been stopping it's forward movement just about when the extractor comes in contact with the notch in the chamber. I have a multi-adjustable gas valve and shoot many kinds of loads; mostly 1oz slugs. I haven't noticed if this problem is more apparent on different settings or with different loads - I think it happens independent of those variables. My first thought it to add a stiffer recoil spring but haven't located one yet. I may have to go to a spring maker in Phoenix and see what they have in stock. My only other idea is to have the bolt contoured and polished. That can get pretty expensive and takes the gun out of comission for a decent period of time. Does anyone know what's most likely the problem here and what's most likely the easiest solution? And is there anything else I should be looking at that I've overlooked?

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Is this happening when firing, and does it happen if you pull the charging handle back to the most rearward position and release it? Mine will stick like that if I hand cycle it easily. If I let it fly home it locks right in though.

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Disassemble the bolt and clean it! The extractor claw is massive, and is one place where a little dirt can cause problems. Mash the ends of the pins slightly when reassembling the bolt as they can sometimes get loose and cause problems.

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I've had this 12 for well over a year now and it's always been very reliable until fairly recently. Much too often the bolt has been stopping it's forward movement just about when the extractor comes in contact with the notch in the chamber. I have a multi-adjustable gas valve and shoot many kinds of loads; mostly 1oz slugs. I haven't noticed if this problem is more apparent on different settings or with different loads - I think it happens independent of those variables. My first thought it to add a stiffer recoil spring but haven't located one yet. I may have to go to a spring maker in Phoenix and see what they have in stock. My only other idea is to have the bolt contoured and polished. That can get pretty expensive and takes the gun out of comission for a decent period of time. Does anyone know what's most likely the problem here and what's most likely the easiest solution? And is there anything else I should be looking at that I've overlooked?

 

Springs would be my last resort you are just masking the problem but I believe you can use 1911 springs.

 

Check the locking lugs on the bolt and trunnion where the lugs lock in for wear. Also check that slot on the barrel for the extractor has wear or metal protruding.

 

Re-profiling the bolt may help but I doubt it since your gun worked fine before.

 

Also check the bolt face for wear, sometimes the bolt is hitting the trunnion or barrel and causing the bolt carrier to shift over as the bolt goes into battery.

 

Something has changed so look for wear that doesn't look normal, I spent a few hours on a brand new race gun that was doing something very similar, with a little filing and massaging I finally got it just right.

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I sppreciate all the info. I forgot to mention that this happens when shooting ( 1 of 10 rounds ) and when hand cycling. It happens even after the gun is very clean and seems to happen with any magazine or load. I will look harder at everything and look for wear, etc. Thanks again all.

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What chamber "notch" exactly are you talking about? Pics maybe? Also im for looking at Anything that is different from before. A good take EVERYthing apart and clean it never hurts too (unless you ass it up putting it back together.) Look at everything rivets included. Just trying to eliminate the most random things that could end up making a difference and leaving you scratching your head.

Has it been a long time sice it was fired last? Maybe something like the extractor as said before could be gummed up a bit.

Edited by sneaky
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I appreciate all the input. The only way it could get cleaner would be if I were to put the while thing in an ultrasonic cleaner. And I am going to try lubricating everything with slode-glide lite. I started using it on my Sig Sauer P229 and it made a noticeable difference in how smooth everything seems to function.

 

Sneaky, if you close your bolt and stop approx 1/2" short you'll see where the extractor first makes contact. It enters a slot about 3/4" long before it actually makes contact with the first and only thing it makes contact with - that's when the bolt tends to get hung up. I'll double check everything even the rivets. The gun never sits long inbetween shooting sessions; never more than 2 weeks and I clean it every time as if it were going to be stored for an extended time. Thanks you for your ideas.

 

Caged, yes, it apears that the gas block is on the barrel straight. I do notice that the finish has been worn off the bolt carrier just forward of the charging handle where the notch is cut into it for bullet clearance when ejecting - I'll give that a good looking at and see if that is hitting something at the right time to be the culpret. Other than that the carrier bolt seems normal and the operating rod seems fine. Thank you.

 

NinerRider, I'll double check to see if perhaps the there's anything that can be causing the the bolt carrier to be shifting over. Thank you

 

Everyone else, I do appreciate all the input and will re check everything everyone has suggested.

 

I just remembered that I goofed up last year and stored the gun for a few months with the bolt locked open. Wouldn't this chenge the memory and weaken it? That may be why I forst thought of using a stronger spring. Perhaps after I've tried everything else I'll order an OEM spring and replace this one. If none of that works I'll go ahean and spend the money to have the bolt professionally polished. I've read excellent things about Pauli's work and have contacted him about his Glass Bolt process.

 

AH, another thing I just noticed is that if I manually close the bolt and watch from the underneath side it is hanging just when the bolt begins to rotate - that gives me something a little more specific to look at.

Edited by Scott Gwin
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Storing the spring compressed is fine. There is a very common misconception that prolonged compression is harmful, If that were so, nothing clocwork would work for long. Your suspension would go limp... Testing for engineers has shown that springs are weakeded by excessive heat, corrosion, over-compression, over-extension, and too many compression cycles. Prolonged compression is ok.

 

I store mine locked back every day except when I am shooting it or practicing a drill.

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GunFun - that's what I had always thougt. OK, back to looking for less obvious things. I guess it's time to look at everything for the umteenth time.... It has me stumped so maybe I need to go shoot a variety of loads through all my magazines all over again and even try every variation on a couple of different gas valve settings. I have a gut feeling that, in the end, having Pauly polish the bolt and carrier is going to fix the problem but that still won't tell me what changed to make this issue surface.

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I'm guessing that your lock up lugs have worn a bit or you've got debris inside your bolt. I don't remember seeing if you have pulled the bolt apart and cleaned it up, if you have, please disregard my bolt comment.

Edited by Caged
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Is this happening when firing, and does it happen if you pull the charging handle back to the most rearward position and release it? Mine will stick like that if I hand cycle it easily. If I let it fly home it locks right in though.

 

Im pretty sure they're all like that.....

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Is this happening when firing, and does it happen if you pull the charging handle back to the most rearward position and release it? Mine will stick like that if I hand cycle it easily. If I let it fly home it locks right in though.

 

Im pretty sure they're all like that.....

 

IIRC his is stopping on the extractor ramp while firing, bad, very bad, because the weapon will fire and it's not completely in battery...

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OK, problem solved. Yes, it was stopping just where it could fire without the bolt being completely closed. I took a dremel to the bolt and smoothed off a couple of sharp edges, cleaned everything once again and lubrigated it with medium Slide-Glide. After that I fired several diferent loads from Walmart cheapie stuff to 3" Magnum 00 Buckshot and did so with different magazines like a 5-round stick, 10-round stick, 10-round drum and 20-round drum and didn't have any problems at all and I shot nearly 100 rounds that day.

 

After having this positive experience with slide-glide I've cleaned everything I have and used slide-glide on them. I'm sold on the stuff. Here in the Phoenix area sand and grit seems to get on and in everything but nothing seems to stick to slide-glide. Also, it stays exactly where you put it and the slipperyness of it can't be beat.

Edited by Scott Gwin
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