Shimming Barrel Extension

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[ARCHIVED THREAD] - Shimming Barrel Extension

Posted: 5/24/2015 3:12:14 AM EDT

Anyone ever used barrel nut shims on the extension--->upper side?

Having a feed ramp issue and a little extra meat on the extension would fix it.

I assume I would need to cut a slot into the shim and thread it behind the indexing pin.

Posted: 5/24/2015 9:28:18 AM EDT

[#1]

Quoted:
Anyone ever used barrel nut shims on the extension--->upper side?

Having a feed ramp issue and a little extra meat on the extension would fix it.

I assume I would need to cut a slot into the shim and thread it behind the indexing pin.

View Quote

M: I would not do that. I could be wrong, but introducing a shim into that critical interface could degrade accuracy. The flange on the barrel extension needs a clean, flat surface on the receiver to seat properly. Instead, I suggest you use your trusty Dremel tool, with a small conical stone and some rubber abrasive tips, to blend and polish those feed ramps. Don't worry about removing some of the anodizing, its of no consequence. - CW

http://www.dremel.com/en-us/Accessories/Pages/default.aspx

Posted: 5/24/2015 11:12:52 AM EDT

[#2]

Quoted:
Anyone ever used barrel nut shims on the extension--->upper side?

Having a feed ramp issue and a little extra meat on the extension would fix it.

I assume I would need to cut a slot into the shim and thread it behind the indexing pin.

View Quote

Lacking a pic, it sounds like the receiver ramps are proud (above) of the barrel extension ramps.
If so, it should feed as is.

Posted: 5/24/2015 11:59:14 AM EDT

[#3]

I would re-work the feed ramp long before I would try what you're suggesting.

Posted: 5/24/2015 4:48:13 PM EDT

[#4]

The barrel ramps stock out past the receiver ramps. I guess shimming the barrel extension would pull the barrel forward but would also mess with timing/lock up.

Really dont want to blend the barrel ramps but I might have to.

Posted: 5/24/2015 4:55:10 PM EDT

[#5]

Quote History

Quoted:
The barrel ramps stock out past the receiver ramps. I guess shimming the barrel extension would pull the barrel forward but would also mess with timing/lock up.

Really dont want to blend the barrel ramps but I might have to.

View Quote

OK, maybe you have rifle ramps on your barrel extension and M4 ramps on your receiver ?

Posted: 5/24/2015 6:51:18 PM EDT

[#6]

They ar m4/m4, just over lap the receiver some.

Already have a thread on this but here is a pic for ref.

Posted: 5/24/2015 6:58:25 PM EDT

[#7]

Oh, that's that Aero Precision thing.
http://aeroprecisionusa.com/aspx/general/media.aspx?mediaid=24
As stated in the other thread, they are both AP parts....why not make them fix it ?

Posted: 5/24/2015 7:04:49 PM EDT

[#8]

Those feed ramps appear to have been cut AFTER the receiver was Anodized.

Posted: 5/24/2015 7:14:48 PM EDT

[#9]

I think you're seeing a reflection off the barrel extension's ramps onto the lower's ramps.

Posted: 5/24/2015 7:21:04 PM EDT

[#10]

Wait did you say you over lapped the reciever? As in you were lapping it and you went to far?

Posted: 5/24/2015 9:21:22 PM EDT

[#11]

Quote History

Quoted:
Wait did you say you over lapped the reciever? As in you were lapping it and you went to far?

View Quote

Look at the pictures. The barrel extension's feed ramps stick out over the lower receiver's ramps. The barrel's ramps "overlap" the receiver's ramps.

Posted: 5/25/2015 3:32:05 PM EDT

[#12]

The feed ramps in the upper look off.
I think a conversation with the seller or manufacturer is in order.

Posted: 5/25/2015 6:03:36 PM EDT

[#13]

aero says shoot it and report back. Not really happy with that answer.

Posted: 5/25/2015 8:26:02 PM EDT

[#14]

Quote History

Quoted:
aero says shoot it and report back. Not really happy with that answer.

View Quote

I doubt you will have any problems. It looks as though the protrusion of the BE ramps above the receiver ramps is .003-.005". I would bet that is well within spec. My SBR is Rifle receiver/M4 barrel ("OK" picture above) and feeds without issue. The reciever never even gets a mark from contact, only the ramps on the barrel extension.

Posted: 5/25/2015 10:05:58 PM EDT

[#15]

I had a similar issue with an aero build using their upper and barrel. When shooting the bullet would catch on the lip and jam. I was in a hurry to use the rifle so I blended the ramp into the barrel to fit the upper.

Edit=damn kindle keyboard

Posted: 5/26/2015 11:14:56 AM EDT

[#16]

Quote History

Quoted:
aero says shoot it and report back. Not really happy with that answer.

View Quote

If your regular ammo does not have problems try some ammo with different bullets.
I am not going to say it won’t work, but that is not what I have seen in any of my builds.

[ARCHIVED THREAD] - Shimming Barrel Extension

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