Badly misaligned feed ramps on Colt upper... something to worry about?

[MarkG]

Not sure what you mean by this statement.

Colt has sold plenty of conversion kit uppers from the mid 1980s until now that came in a brown cardboard box with the upper inside the box in a sealed bag.

The blue presentation box ones from 2010 to 2011 are just more recent.

The upper in question in the OPs post is just a case of less than stellar workmanship. This upper probably has a C AF forge code?

Never say never... I stand corrected.

[Failure2Stop]

Does a bolt properly engage the barrel extension when the upper is fully assembled?

[Liftrat]

Not to take this thread too far off track, but I've heard that the anodizing on 1911 aluminum feed ramps helps protect the softer metal underneath. Wouldn't this also be the case if one took a dremel to the upper in question? If the upper's ramps are what's off, light grinding looks to be the easy fix, but would it cause more problems in the long run? Just curious.

[kwilkin]

Not sure what you mean by this statement.

Colt has sold plenty of conversion kit uppers from the mid 1980s until now that came in a brown cardboard box with the upper inside the box in a sealed bag.

The blue presentation box ones from 2010 to 2011 are just more recent.

The upper in question in the OPs post is just a case of less than stellar workmanship. This upper probably has a C AF forge code?

It does per the OP's pics.

[scottryan]

It does per the OP's pics.

There is only one picture in the OP showing the inside of the upper so I'm not sure how you know this from looking at the OP.

[kwilkin]

There is only one picture in the OP showing the inside of the upper so I'm not sure how you know this from looking at the OP.

He followed up in post 7:
https://www.m4carbine.net/showthread...89#post1881189

Granted, he could have embedded them rather than linking the way he did.

[scottryan]

The upper in the OPs pictures is indeed factory assembled. All the forge codes and codes on the bolt are of a matching early 2000s upper.

[recce556]

From my understanding, a factory built Colt upper will have a small proof mark on the upper next to delta ring on the ejection port side. Here's a pict on a A2 upper, in the mark closer to the ejection port door. On the M4 uppers, it should be in a similar location. Check both sides of your upper.

coltproof.jpg rbfdc4.jpg
(Images from Urban_Ops from a post over at ARF)

I've built over 100 uppers using individually sold Colt M4 uppers receivers (meaning not disassembled from complete uppers) and none of them had the VP ("Verified Proof" from a test fire) proof mark. All the factory built Colt uppers that I have (several) and upper receivers that I've built from "pull downs" all had VP proof marks.

[Hygienist]

Thanks for the help so far everyone.

To answer some questions:

Does the bolt engage the extension?
I don't have a ton of experience on the AR15 platform, but based on a Colt AR15A4 I had for a bit (not any longer), the bolt seems to engage like it should. The bolt lugs go through the barrel extension just fine and the BCG shoves forward into place as it should.

Canted FSB?
Near as I can tell, the FSB is straight and true.

Marking @ chamber swell:
If I get a chance I'll look at it, though again I am inexperienced so it's a bit difficult for me.

[Toddler]

If your bolt is engaging then it's just poorly cut feed ramps on the receiver. At least you know now your fix will be cheap, good luck.