Well, I was off looking for what type of chrome lining the military specifies for its barrels and came across these documents (PDF):
Mil-spec for M16A2 (Inactive for new design effective 1993)
Mil-spec for M4 Carbine
Amendment 1 to M4
M4 Revision A
M4 Revision A Amendment 1 (Inactive for new design effective 1994)
They've got them for the M16 and M16A1 as well but apparently those documents are subject to controlled distribution while the more current ones aren't. Go figure.