Friend of mine got what appears to be a AR Build. The lower is a JD Machine with a serial number and all caliper engraving.  The upper has a white X on the top of the rail near the charging handle. the front of the upper it looks like a milled out X where the gas tube enters the upper. the rifle doesn't have a gas tube or gas block. it has a free floating hand guard. the upper also has the CERRO  forge keyhole stamp. im just trying to help him out.
i guess he just needs a gas tube and block to make this weapon whole. I personally would like to know who manufactured the upper. The barrel is 5.56mm and is  1 and 7. No manufacture markings that we found. any help will be appreciated.

T

Pictures?

Cerro forged it, but if there is no manufactures mark, then it will be nearly impossible to actually figure out who did the final milling on it.  A lot of companies that do their own milling use the Keyhole forge marked uppers and lowers, I have DPMS, I have a Delton, I have a Bushmaster, etc.  I have a lot of uppers and lowers that I don't know who milled them, just know the company that sold them.

Yeah that would have been nice. Next time I visit. I'll take a couple of pictures.

Almost impossible to answer. Never seen an upper with the "X" markings you describe.

Red X Arms upper.

Wow, you nailed it. Thank you for finding that for us.