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4/4/2009 6:29:33 PM EDT
has anybody ever twisted, or seen an upper that was twisted?  i noticed a pronounced cant when i installed an acog on a rifle that i built using all bushmaster parts.  after removing the scope, the fsb appeared canted compared to the rail top of the receiver.  after removing the barrel, and using a laser to confirm that the tab on the extension lines up with the fsb, all i can assume is that the upper receiver is twisted a little bit, or somehow out of spec.  has anybody ever seen this, and / or can you think of a good way to measure the upper and "prove" it is twisted?

-frank
4/4/2009 7:38:55 PM EDT
[#1]
Does the BCG bind at all in the receiver? If not it probably isn't twisted. I suppose the rail could be off but I would bet it is the front sight base that is canted. Unless you have a way to precisely line up the laser with the barrel you probably have too much error.
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