Do the Forge codes on FN uppers somewhat correspond to the year of manufacture when referring to complete M16A2 uppers? With Colt it somewhat does but I was not sure about FN. I think FN would get bids for a forge to supply the raw forgings and once the contract was near complete fulfillment would seek new bids and thus the reason why the source of the raw forgings would change, but when did each change occur?

The forging codes for A2 uppers with final machining by FN are listed below and the approximate time frame ranges are listed when known. Does any one have more accurate data to complete this table.

F K
Both letters are raised. K signifies Kaiser Aluminum. (First uppers used on production FN M16A2 and were used regularly from 1988 until ?)

F M
The F is raised. and the M is stamped. M signifies Martin Marietta. (Approximate time frame late 90's to early 00's, any one have a more exact range ?)

F MB
All letters are raised. MB signifies  Mueller Brass Company. (Unknown date range)

F A
Both letters are raised, and the A is splintered. A signifies Anchor Harvey forge.  (Unknown date range.)

F keyhole
The keyhole symbol is raised and the F on these is stamped. Keyhole signifies Cerro forge.  (Unknown date range.)

F keyhole
The keyhole symbol and the F on these are both raised. Keyhole signifies Cerro forge. (Final A2 uppers used on production A2 from FN I think but this needs to be verified.)


Also I am not sure is an F M marked uppers were made with both letter raised at any point.

I have a Slick-Sided Upper that has FK that is raised.  The guy I got it from said that it was a 9mm Upper, but it does has the standard Gas Tube Clover Leaf hole.

Also of note, is that it's Front Pivot Pin Leg is also Rebated, just like my FK marked FN A2 Upper Receiver is.

I wish I could get my hands on a box of these FN FK Slick-Sided Upper Receivers!!!  It's also of the Square Forged design.

Please keep discussion on topic with relevant info to dating A2 uppers from FN only. Interesting upper and all but I don't think it really assist with what I am trying to document and substantiate in this thread.

I have a FNMI complete A2 upper.