Can misaligned M4 feed ramps be adjusted > Build It Yourself

Posted: 12/8/2007 10:44:07 AM EDT

I just received this upper half. As you can see, the M4 ramps are misaligned. Is this something I can fix myself or does it need to go back to the factory? I have all the tools to install a barrel.

Posted: 12/8/2007 11:57:59 AM EDT

[#1]

Was there slop in the alignment pin and the upper? If not the extension is off and I'm thinking that it would have to be adjusted somehow. I'm sure someone will be along to comment. If there was some play in the alignment pin and the upper you may be able to wedge it making the ramps line up.

Posted: 12/8/2007 12:03:47 PM EDT

[#2]

Will the bolt go in and lock up.This will let you know if its the extention or maybe the upper was just machined wrong.

Posted: 12/8/2007 12:36:33 PM EDT

[#3]

it appears to me as though the ramps in the barrel extension are not machined correctly.
look at the locking lug cutouts in the ramps. they should be centered.
the ramps in the pic are clearly off to the right

Posted: 12/8/2007 1:49:51 PM EDT

[#4]

crackedcornish, you nailed it. Now that I look at it again, everything appears machined correctly except the feed ramps in the barrel extension. This one's going back for replacement. Thanks guys!

Posted: 12/8/2007 2:01:23 PM EDT

[#5]

Dude, CLEAN that thing!

CJ

Posted: 12/8/2007 3:38:37 PM EDT

[#6]

That's the way it came from the factory. It's the crud from test firing. No point in cleaning this one since it's going back.

Posted: 12/8/2007 3:40:30 PM EDT

[#7]

yeah, certainly its the extension, never seen that before though. interesting.

Posted: 12/8/2007 4:39:54 PM EDT

[#8]

Where did you get the barrel from?

Posted: 12/8/2007 5:22:44 PM EDT

[#9]

It's an Armalite upper half from their Thankgiving special. I received five other upper halves that were all fine.

Posted: 12/8/2007 7:25:16 PM EDT

[#10]

<---------- Dashes off to check his.

Posted: 12/10/2007 2:40:24 AM EDT

[#11]

That's far enough out of rotation that I'd be afraid to fire it. Bolt lockup may be iffy there. Somehow your barrel extension is out of alignment. That's not easy to fix. I'd send it back if I were you.

Posted: 12/10/2007 3:02:41 AM EDT

[#12]

Is the front sight canted?

Posted: 12/10/2007 4:31:05 AM EDT

[#13]

The feed ramps in the barrel extension are the only thing that are out of alignment. My guess is that they were machined with the barrel rotated a few degrees out of alignment. Notice that the slots that the locking lugs travel through are in their correct places. The bolt goes in and locks up fine. I'm sure that there is no danger in firing it, but it's just not right. Keep in mind that the vast majority of the time the bullet tips are going to hit above the portion of the upper receiver that is cut, so reliability might not even be a problem. A simple visual inspection of the barrel extension or completed upper would have been enough to avoid this problem from getting out the door. I've already emailed Armalite for an RMA#.

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[ARCHIVED THREAD] - Can misaligned M4 feed ramps be adjusted