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Help! New M4 bolt hanging/sticking . . .


Bolt_308

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Hello- new to the group as I just bought my first M4 and brought it home last night!  Gun is brand new.  Got it home, followed the directions to clean, lube, and assemble.  Followed some of the direction here and applied a lot of lube.  Right away in working the bolt, something was not right- it was hard to pull back and kept sticking back.  Thinking I had done something wrong, I disassembled, watched a bunch more YouTube videos on disassembly/assembly, and then very carefully reassembled.  Same issue.  Bolt would be difficult to pull all the way back to the locked open position, would ‘hang’, locked back, and it would take a very firm wack with my palm to get it to go forward back into battery. 

I did a lot of troubleshooting, reading of forums.  Made sure barrel fully seated, nut firmly cranked down. I even tried reassembling without the trigger group installed.  In running the bolt without the barrel installed, everything was smooth, but when I reinstalled the barrel, and the barrel extension, it would hang/freeze/stick again.  Eventually, I figured out that the front of the bolt, is rubbing against the ejector, and there is a gouge forming on the underside of the ejector.  I have attached some close up pictures to hopefully better illustrate, as I am still learning the parts and may not have the right name for the parts.  If you look closely on the bottom of the ejector, there is a groove forming where it hits and grinds.  In searching the internet, I did find a forum thread on AR15.com where it sounds like someone had a similar problem and their gunsmith removed some material on the one part of the bolt where it was rubbing to get it working.  Before I do something that drastic, thought I would check here first to see if there is anything I am missing or if this is a common/known problem.  I can link to that thread, but wasnt sure the etiquette here for that.  

Help!  I was so excited getting home with a new M4 and have spend the night and this am trying to get it figured out!  Thanks!  

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Edited by Bolt_308
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Hey @StrangerDanger or anyone else who can- see attached picture.  I spent the weekend troubleshooting the gun.  I had found this post on AR15.com https://www.ar15.com/forums/armory/Benelli-M4---Bolt-stuck/1-508609/ Which after reading it, sounds like the same problem I am having.  I took a small file, and did a light filing to the edge of the divot, which was very sharp and is what is digging into the ejector housing.  By doing that, I now got the bolt to cycle and function instead of binding.  Locking the bolt back, I can see that the bolt is ‘canted’ slightly, and was wondering if this seemed normal compared to any of your M4s out there.  As you can see from the pic, the ejector divot is not centered on the ejector housing, and wondering if that is normal?  After calling Benelli this AM, they want to have me send it back to them, which of course I can do but will be several weeks, and just sucks after being so excited to finally have an M4.  So before I do that I thought I would check to see if that looked normal or not?  Thanks all!

 

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Edited by Bolt_308
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2 hours ago, D'zaster said:

Were you able to cycle the action at the gunshop? 

Unfortunately I ordered it online from Sportsman’s Warehouse.  When I picked it up, it was still in the box taken apart, arrives with barrel and bolt out.  I took out the items and inspected them, couldn’t see any wear or issues, but since this was my first M4, I didnt know the procedure to assemble it, and so just left it in the box.  Now that I have some time with it I would know there was an issue, but even if I had put it together and it was doing it, unfortunately I probably would have thought it was user error.  And the staff at Sportsman’s Warehouse I am sure would not have known, at least the ones that were working that day.  Hard lesson learned, uggg . . .

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I’d send it back rather than chance shooting it like that. The bolt might not be seating fully into battery when the bolt is forward due to that alignment issue. As Unobtanium mentioned, something is likely machined out of alignment.
 

The bolt should be centered properly. My guess is Benelli will replace the bolt carrier group and the barrel assembly.
Unfortunately it will take several weeks to have corrected. 

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1 hour ago, StrangerDanger said:

I’d send it back rather than chance shooting it like that. The bolt might not be seating fully into battery when the bolt is forward due to that alignment issue. As Unobtanium mentioned, something is likely machined out of alignment.
 

The bolt should be centered properly. My guess is Benelli will replace the bolt carrier group and the barrel assembly.
Unfortunately it will take several weeks to have corrected. 

The bolt seats very early in the cycle. You have significant carrier movement prior to any unlocking/bolt rotation. I agree that it needs to go back to benelli, just wanted to touch on this.

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What’s going to be extra fun is that I ordered pretty much every accessory out there for it, and so those orders are going to start coming in right as I send it out.  I guess if I try to look on the bright side once it comes back hopefully that means I can go to town decking it out with all the goodies . . . ?

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