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Gap between upper and barrel nut


rogtack

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Hey guys, this is my first build and I didn't find anything with the search feature. I received my Rainier Arms barrel and MI hand guard today. I snugged everything down by hand just to make sure it all fit correctly and there's a gap between the barrel nut and upper. The gap is .154". Is this gap normal??? Or will it seat all the way once it gets tightened with a torque wrench? It's a Cross Machine Tool upper. Thanks.

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post-15552-0-02026900-1421809435_thumb.j

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 And as long as the Barrel's seating flange is seated flush against the Upper receiver & a notch on the Nut for the gas tube line up  . From your photo ,the seating of the rail to rail , the Hand guard is not going any further, but that doesn't mean the Barrel nut will not go further in , when torqued properly  .

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  • 1 month later...

I just experienced this on my PSA 308 AR after I installed the MI handguard.  The gap created here allowed my dust cover pin to walk forward while shooting and come out of it's rear pin locator hole.  The dust cover stayed attached but it looked like it was about to fall off.  I have not found a solution yet.  It appears your rifle does not have a dust cover, correct?

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Thanks for the heads up on that dust port cover.  Here is the link for anyone interested:

http://www.brownells.com/rifle-parts/receiver-parts/ejection-port-cover-parts/ejection-port-cover-assemblies/pin-less-ejection-port-cover-assemblies-prod73296.aspx

 

I came up with a temporary repair for the time being.  I gutted a length of paracord and wrapped it around the threaded portion of the receiver and tied it.  It stops the ejection port cover pin from walking forward enough to prevent it from falling out.  Crude, but it works.  I'm thinking I might make a longer dust cover pin or cutting a groove to install a C clip.  Here is a pic of what I have now:

FullSizeRender12.jpg

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C-clip on pivot pin may not help, but cause enough resistance to stop pin movement  . That para cord my melt in there & cause problems with easy removal . You could also make an extension , albeit ,a thin walled one , that would restrict its movement enough so the cover pin would not come out of the blind end in the Receiver .

  A large C-clip in that gap attached to the Upper Receiver Barrel nut threads , but you would have to remove the Barrel nut to install it .

Edited by survivalshop
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I think you're right about it melting.  I looked at it closely afterwards and it's just barely touching the gas tube.  Not sure on the melting temp of paracord but that gas tube gets toasty.  5.56 AR's use a small C clip to prevent the dust cover pin from walking rearward.  Not needed on the 308 as the rear hole in the receiver is blind.  I'm considering removing the pin and welding an extension on.  Or finding 4.5" of .125" diameter steel pin...

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