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Posted

Hey guys,

I need to lap the receiver extension, it is a little to long. From what I've read Aero's are known for this. I am mating a Faxon barrel to it with a Fortis Switch hand guard. When I put it all together there is a gap between the Fortis and the Aero upper about 1/8", also the barrel pin is about 1/16" from fully seating in the extension. The barrel extension does not reach the feed ramps also, there is a small step from the receiver ramps to the barrel ramps, looks to be about the 1/8" I need.

 

Thanks

Posted

Hey guys,

I need to lap the receiver extension, it is a little to long. From what I've read Aero's are known for this. I am mating a Faxon barrel to it with a Fortis Switch hand guard. When I put it all together there is a gap between the Fortis and the Aero upper about 1/8", also the barrel pin is about 1/16" from fully seating in the extension. The barrel extension does not reach the feed ramps also, there is a small step from the receiver ramps to the barrel ramps, looks to be about the 1/8" I need.

 

Thanks

Your not gonna lap off that much material without screwing it up.  The barrel itself is fully seated but nothing lines up? Any chance you can post a picture?

Posted (edited)

 The important thing is , is the Barrel Extension seating Flange , fully seated against the Face of the Barrel Nut Threads on the Receiver ? The Upper Receiver may not be a M4 type as you may be used to , there will be a transition area . You need to check the Extension Flange & make sure its seated. If it is , assemble , Check Head Space & do a Function test with a Dummy round .

  Photo's, as said , would help 

Edited by survivalshop
Posted

If you set the barrel back 1/8 inch you could also run into a problem with the back end of the bolt carrier sticking out from the back of the upper receiver too far.

Posted

If you set the barrel back 1/8 inch you could also run into a problem with the back end of the bolt carrier sticking out from the back of the upper receiver too far.

That is another thing I was thinking, besides it looking ugly! 

Posted

Also the barrel extension pin is about 1/16" from being fully seated in the receiver slot.

  That in itself means nothing if the Flange is seated .

     Have you fully assembled this firearm & there was a problem or is this your observations , just test fitting the Upper ? The Fortis hand guard gap is a separate issue . You may have to fully assemble & torque the barrel nut , to see if the gap reduces or is eliminated .

    Someone here I'm sure has used this Hand guard & will know . Some hand guards do not seat fully against the Upper Receiver & some like the older JP hand Guards , say not to seat them against the Upper Receiver .

   The photo's I see on various rifles , show a slight gap between the Hand Guard & Upper Receiver .

Posted

http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/receiver-tools/ar-15-m16-upper-receiver-lapping-tool-prod20220.aspx

This one is available for AR-15, but I don't think they have one for a .308.  I've used this one a couple of times, on AR-15s, and it works great, but mainly just for truing up.  I'm not at all certain shaving a bunch off the length of the receiver extension with a tool like this - or any other tool, is a good idea, as noted by others.

Posted

Based on your description, your barrel extension could also be off spec. If the shoulder is set back too far, it would explain quite a bit of your issues. Not saying that's the issue, but it would be on my list of possible suspects.

Posted

Yep the flange is flush against the receiver extension and it is an m4 receiver. Will try to get pictures when I get back home!

If you have issues with posting pictures send me a pm and I'll help you out

Posted

Maybe there is a market for "308" lapping tools,I haven't really seen any.  Might just make a few.. 

 Has anyone tested to see if there is any difference between a lapped & non-lapped Receiver ? As far as how the Rifle shoots or operates . 

 If there is an issue with this rifle as far as the Barrel Extension ( doubtful ) a lapping tool would not help .

Posted

  That in itself means nothing if the Flange is seated .

     Have you fully assembled this firearm & there was a problem or is this your observations , just test fitting the Upper ? The Fortis hand guard gap is a separate issue . You may have to fully assemble & torque the barrel nut , to see if the gap reduces or is eliminated .

    Someone here I'm sure has used this Hand guard & will know . Some hand guards do not seat fully against the Upper Receiver & some like the older JP hand Guards , say not to seat them against the Upper Receiver .

   The photo's I see on various rifles , show a slight gap between the Hand Guard & Upper Receiver .

yes, I did assemble the rifle, and noticed all these issues. I know the hand guard is cosmetic, but it looks like crap! I did torque the barrel nut and the gap did not close. It seems hit and miss on other forums other guys have the same issue, and others mate up perfectly! I've put together enough ar's to know this is a large gap!

My main concern though is the 1/8" step from the receiver feed ramps to the barrels feed ramps!

Posted

Based on your description, your barrel extension could also be off spec. If the shoulder is set back too far, it would explain quite a bit of your issues. Not saying that's the issue, but it would be on my list of possible suspects.

I was wondering that as well. Another guy had his flange turned down, originally was,125" and turned it down to .121". My flange measures. 135".

Posted

If you have issues with posting pictures send me a pm and I'll help you out

thanks, I will! If I can get back home before the big storm hits this weekend!

Posted (edited)

 If there is an issue with this rifle as far as the Barrel Extension ( doubtful ) a lapping tool would not help .

This has already been established.

 Has anyone tested to see if there is any difference between a lapped & non-lapped Receiver ? As far as how the Rifle shoots or operates . 

 

Given the popularity of the AR15 lapping tool I'm sure people would be interested in the 308 version.

Squaring the mating face of the receiver in relation the the bolt carrier is certainly not going to hurt.

An added benefit to some is the ability to take off just a little to help with torquing that barrel nut into the sweet spot.

 

Now back to brother 82Halo's current problem.

Edited by Toolndie7
Posted (edited)
 

This has already been established.

Given the popularity of the AR15 lapping tool I'm sure people would be interested in the 308 version.

Squaring the mating face of the receiver in relation the the bolt carrier is certainly not going to hurt.

An added benefit to some is the ability to take off just a little to help with torquing that barrel nut into the sweet spot.

 

Now back to brother 82Halo's current problem.

 Don't get me wrong , I lap all of mine , but only the last item,  of the above , those other items may be a added benefit , I lap to make sure I have a good flush Flange seating surface .

    82Halo 

 Have you cycled a Dummy round through this rifle & had issues  or have you test fired it ?

Edited by survivalshop
Posted

 Don't get me wrong , I lap all of mine , but only the last item,  of the above , those other items may be a added benefit , I lap to make sure I have a good flush Flange seating surface .

    82Halo 

 Have you cycled a Dummy round through this rifle & had issues  or have you test fired it ?

made it home! Will get some pictures when I take a break from shoveling and snow blowing! 

Unfortunately I don't have any 308 dummy rounds! Not test fired, and now don't know when that can happen!

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