Thanks for the link. I have read through the thread, and although there are a few people bitching about non-F marked FSB's, there are no [B]actual[B]accounts of the non-'F' marked rifles failing to zero.
For the record, my Colt A4 upper is 2/14 production, non-F marked FSB, and 'short' fsp. Zeros perfectly with both a Matech BUIS and a Colt carry handle.
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