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11/20/2006 5:39:52 PM EDT
Hi,
I already posted in the main AR forum, but I'm posting it here as well
hoping to get some more opinions.

I bought a stag 2H upper a few months ago... It's a 16 inch M4-profile barrel,
with an ARMS40A2 rear sight and an F-marked front sight.
I tried to zero it at 25 meters...  Had to raise the front sight way too much
(in my opinion) to get the POI down.  I also tried using stag carry handle sight
instead of the ARMS - same result.

I ended-up sending it back for warranty service (for a different problem).
Stag sent me a brand new replacement and I encountered the same issue... Still had
to raise the front sight way too much to get it zeroed, and this one had a canted front
sight as well.  I also tried an eotech 512 - that shot way too high at 25 meters
(8-12inches) and I had to crank that down a lot.

Pissed at the front sight situation, I chopped it into a low profile gas-block and put a
MI 10inch railed free float on the upper, with an LMT rail-mount front sight. The elevation
problem still exists....

So... I'm thinking that the upper receiver is machined improperly and the barrel is
pointed slightly upward.  Any idea of how to verify this or how to fix it?
I'm thinking of putting a shim in between the barrel and upper receiver to try
and correct it (I kinda doubt this will work).  Or should I try buying a new upper receiver?

BTW, I tried the bushmaster taller front sight post and that helps a little bit,
but it isn't a real solution, since the top of the post would be too high
(ie. above the ears/guards).

thanks,
jjk
11/20/2006 7:16:05 PM EDT
[#1]
Oblong shimming will not work,

What distance are you zeroing?

If all else fails, there is always the option of calling the manufacture for advice on the subject, and possible a replacement.  
11/21/2006 4:06:26 AM EDT
[#2]

Quoted:
Oblong shimming will not work,

What distance are you zeroing?

If all else fails, there is always the option of calling the manufacture for advice on the subject, and possible a replacement.  


Thanks.
Trying to zero at 25 meters...
The only reason I thought the shimming might work, is that I noticed some up/down play of the barrel
in the receiver socket when the barrel nut is removed.

What are the odds that replacing the upper receiver could fix the issue?
They're not that expensive, but I don't want to go through all the work for nothing.
11/21/2006 4:18:46 AM EDT
[#3]
You should have a much tighter fit of the barrel to receiver.  Every Colt upper I have barreled was a light driven fit of the barrel to receiver.

Try a better grade of parts.
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