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Discussion Starter · #1 ·
I have an upper assembly with no markings on it. The only marking is "4BI2" on the front sight bar right above the barrel.

Any suggestion and there is no barrle markings. How can I tell if it is chrome lined or not?

It shoots ok, 1-1.5 MOA at 100 yards so I'm hapy with rifle but would like more information.
 
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Discussion Starter · #2 ·
one guess is as good as another ;)
the marking on the FSB are the code for whoever forged the casting.
 
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Discussion Starter · #3 ·
Look at the chamber. If there is a shiny ring around it, it is chrome-lined. You can also see a small shiny ring around the muzzle as well. Not sure about your barrel codes.
 
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Discussion Starter · #4 ·
Thank you, I'm still trying to find out who made this upper.
It looks like there is an image or stamp of a lock o one side of the upper above the extraction port. ( a little towards the charging handle)
 
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Discussion Starter · #5 ·
That mark is the forge mark of Cerro Forge, looks like a "keyhole"
Cerro makes the raw forgings for alot of companies.
 
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