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Posted: 5/26/2013 8:12:24 AM EDT
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Thanks for the replies guys. So I re-measured the distance from the barrel journal to the top of the front sight at 1.96" for the barrel in question (see pic below).
I also measured two CMP C marked barrels with unmarked FSBs and a CMP Chrome Bore marked barrel with a raised "C" and "bell" marked FSB. All three barrel FSBs measured in at 1.96", so this appears to be a non-issue. 
I may have already answered my question but here goes anyway. I have a new in wrap 20" chrome lined (CM P Chrome Bore marked) 1/12 A1 profile barrel with an FSB that has a forge code with a raised "F" on the right hand side (no markings on left hand side) and a square A2 front sight post that I plan on mounting to an A1 upper. I read up on the "F"-marked FSBs in other posts (which indicated that the "F" mark should be stamped on the left side of the FSB; or not at all in some cases). I also measured the distance between the barrel journal and the top of the FSB where it's machined out at 1.97"-ish (0.198" for F-marked, 0.194 for standard A2 FSB per link below). Based on what I read I'm thinking that I don't have a problem, but I was also wondering if I'm measuring to the wrong reference, since the A1 sight bases are drilled to 0.625" instead of 0.750" (A2), which would increase the distance from the barrel journal to the top of the sight base (for an A1). Let me know what you think as I may have to dispose of this defective part... 
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I have one that sounds just like yours & have no sight issues with it. It is not a M4 "F" marking (as you said, it would be on the left side & stamped), just a forge code.
BUT, if you need to "dispose" of it as a defective part I would take that burden off your hands & dispose of it for you. 
ETA: After going & looking at it, mine does not have a F forge code on it. It has a Y with other jibberish like in Ekie's guide. (Picture & text borrowed from there.) Colt M16A2 conversion kits/replacement barrels, M16A4 FSB's and late replacement M16A1 barrels have a jibberish forge code: 
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I know that you don't have an M4 style "F" marked front sight base, but for what it's worth there does not seem to be any adverse effect caused by using "F" marked front sight bases with A1 or A2 uppers, and if you intend on using the 50 yard / 200 meter IBSZ zero with a fixed handle upper it may actually be beneficial to have an "F" marked sight base. I've got both a 20" and a 16" mid-length with A1 uppers an "F" marked bases.
Besides, a standard post made shorter to fit will still be protected by the "ears", while standard FSBs with a longer post sometimes lose that protection. |
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