I have a Colt preban with bayo lug and FH but not sure if its the original upper that came with the rifle because as far as I have ben able to find, Blue Label guns(which this is) did not have bayo lugs.  Barrel markings are:

C MP 5.56 Nato 1/7

Any way to find if the bore and chamber are chrome lined?

I called Colt they said I would have to pay for them to have the historical guys research the gun's specs.  Seems like BS to me.  I'm sure one of you guys would know.  I'm just curious to know.  Any other markings on the upper or barrel to indicate this?

TIA

O.K. one more time "C" Chromed chamber.  "MP" Magnetic Particle tested.  Now if you don't believe that go here [url]www.biggerhammer.net/ar15/barrelsbolts/[/url]

CIB, not true.  I had a Colt POST ban that did not have the chrome lined bore labeled "C MP".  The "C" is merely for "Colt".  Hence Bushmaster's markings of "B MP".

JohnM is correct.  A visual inpsection will determine if it has the chrome bore.  Inspect from the barrel end itself in bright light.  If there is chrome lining you'll be able to see silver at the very end of the barrel face with just a bit of overlap on to the crown.  Also NOT all Colt military profile barrels will have the chrome lining, i.e., a 20" HBAR.

Good shooting.

CMOS

It is a 20" HBAR.  I have examined the crown and there is a silver edge to it(tough to see with that FH in the way).  So I guess it chrome lined after all.  The chamber is bright and shiny too.  Thanx!