Trouble mating DD A4 Upper onto Colt lower

AR/M4 AR Technical Discussion
1

Hello I am trying to mate a DD A4 Upper onto my Colt lower, as much as I try I can’t get it to work. This same lower can mate to my Larue Stealth upper with no problems. This is the lower that came with my complete Colt 6721 by the way.

I also tested the DD A4 Upper on an Aero Precision lower and LMT lower. Everyone was a no go.

Here are some pictures hopefully they help:

Is this upper out of spec maybe?

Any advise is welcome, I don’t want to hammer it in, the other uppers mate fine with this lower.

Thanks in advance.

2

Have you contacted Daniel Defense?

3

No, not yet.
The upper is not a complete upper from DD, not sure what to do.

4

Is it just your front pin hole? My DD stripped upper had a problem with the front takedown pin hole being too small. Take a drill bit and see if it fits in the rear hole fine and then see if it fits the front hole. If not then you have the same problem I had. I used a file and carefully made it large enough to fit.

5

I think this is it.

A 1/4 inch drill bit fits fine in the rear hole of the upper, but it does not go into the front hole.

Thanks, I will try your suggestion.

6

The upper receiver is clearly marked Daniel Defense. Please contact them and address the issue.

7

OP;

PLEASE READ THIS.

Sir,

I read your thread on your Daniel Defense upper. It got locked before I could respond.

I implore you NOT to do as this poster said and file the pivot pin lug on your upper.

Daniel Defense is a stand up company and WILL right this for you at no cost to you and no questions asked.

I’ve dealt with their customer service a couple of times. They are top notch and how all businesses in America should be.

You can email Joe Marler and he will help you out at: jmarler@danieldefense.com

Good luck!
Chris.