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1/25/2018 7:38:29 AM
Posted: 10/22/2003 9:35:02 PM EST
I have a pre-ban SPII AR-15 A2 barrel marked:

C MP 5.56 Nato 1/7

Some sources say the whole thing is chrome lined, others say just the chamber.

thank you.
Link Posted: 10/22/2003 9:39:19 PM EST
It looks chrome lined with a flashlight, looking at the crown.
Link Posted: 10/22/2003 10:06:19 PM EST
yeah, its chrome from what i remember the "C" is for chrome and the "MP" is for the magnaparticle(?) testing they did on the bbl for QC (quality control)
Link Posted: 10/23/2003 2:14:50 AM EST
I can't call myself an expert on more recent barrels, but on the early A1 series, "C" stood for Colt, and unless there was also a "B", or "chrome lined" stamped on it, it wasn't. Easy test is to take a Q Tip w/instant blue and put it on the bright ring around the edge of the muzzle. If the bluing takes,and darkens the edge, it's not chrome lined. If it doesn't darken the ring, it is chromed.[:D]
Link Posted: 10/23/2003 5:34:23 AM EST
I read that C stood fro chrome chamber, MP like you said (TOPCREST) for magna-particle, but that it is supposed to say chrome barrel for a bbl. I think I might trie that bluing test. Sounds like a plan, but I am sure I can see a difference between a chrome lining and rhe rest of the barrel, but it is unlike a Bushmaster bbl where the chrome goes pase the bore and onto the crown itself ( a little). This appears to just be the bore itself.
Link Posted: 10/23/2003 8:57:00 AM EST
[b]C[/b] mp Stands for Colt Just as Bushmaster Marks their barrels [b]B[/b] mp
Link Posted: 10/23/2003 10:01:10 AM EST
Correct [b]C[/b] stands for [b]Colt[/b]. Old (we're talking 1960's here folks) barrels had 'C' for 'Chrome lined' - but that was when it was pretty much only Colt and there were military barrels in the system with and without the lining.
Link Posted: 10/23/2003 12:10:01 PM EST
Could be both, my colt sporter has the same markings on the barrel and it's BOTH BORE AND CHAMBER chrome lined, you gotta inspect it visually, is the only way to be sure. HUNTER.
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