Hey all, A friend recently gave me a stripped A1 upper after he replaced it with a new A2 version. He said it was a bushmaster upper, is there any way to check ?
Are there any ID or foundry marks put on them by the manufacturer ?

www.ar15.com/forums/topic.html?id=61976

Production Codes





The production codes listed below are used by the various manufacturers as part of their quality control procedures for their forgings. These production codes can overlap between manufacturers, and cannot be counted on as the definitive source of origin - they do however make a good guideline.

Stamping  Source  
CAF Colt / Alcoa Forge (See above for photo)
CH Colt / Harvey Aluminum (1st Colt Forgings)
CM Colt / Martin Marietta (See above for photos)
DK Diemaco / Kaiser
FK, FS, BK, DK, EK, FK, AF, CW, AA, FS Bushmaster
LK FN / Kaiser
LM LAR / Martin Marietta (Army Spares Contract)
Splintered A Olympic Arms


or check out:

www.biggerhammer.net/ar15/uppers/