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1/25/2018 7:38:29 AM
Posted: 9/26/2002 8:19:52 AM EST
This is my first post here, but I've been lurking around this forum and absorbing information like a sponge for the past month or so.

Here's my question: I recently picked up a Colt MT6731. The barrel is marked "C MP 5.56 NATO 1/9 HBAR". I know that the "C" indicates Colt, the "MP" indicates magnetic particle, "5.56 NATO" is the chambering, "1/9" is the twist, and "HBAR" indicates heavy barrel. But, is this a chrome lined barrel / chamber?

If the barrel is chrome lined, what do you recommend for break-in? If it's not chrome lined, what do you recommend for break-in?

Thanks (very much!) ...........
Link Posted: 9/26/2002 8:22:42 AM EST
Colt HBARs have a chrome lined chamber, but not bore. As for breaking in, I'll let someone else handle that. There's a gazillion different opinions on that!
Link Posted: 9/26/2002 8:31:12 AM EST
Just a follow-up: I called Colt a few minutes ago and the customer service guy stated that the bores haven't been chrome lined since 1998. He further stated that no break-in is necessary and the barrel is ready to go. Any opinions on this?

Thanks
Link Posted: 9/26/2002 8:41:48 AM EST
You mean you got someone other than that lady who reads back the same information that is on the site...and refuses to let you speak to one of their technical reps?????? Lucky you!

I've been in the same quandry for a while. I don't see the tell tail ring at my muzzle, but then again I have a flash hider on mine. I DO see a bright ring down the chanber, right where the bore starts, and the inside of my chamber is bright and shiny. No one can tell me what the deal is...so I no longer give a damn. Just shoot it until it is worn out, then make sure you buy a chrome-lined replacement.
Link Posted: 9/26/2002 9:33:51 AM EST
what is the chrome status on the colt 14.5 and 16.5 m4 profile barrels?
Link Posted: 9/26/2002 9:47:42 AM EST

Originally Posted By mr_h:
what is the chrome status on the colt 14.5 and 16.5 m4 profile barrels?



Those that come from LE upgrade kits have CL bores & chambers.
Link Posted: 9/27/2002 10:47:56 PM EST

Originally Posted By new-arguy:
Colt HBARs have a chrome lined chamber, but not bore. As for breaking in, I'll let someone else handle that. There's a gazillion different opinions on that!



My preban Colt 1/7 HBars have chrome lined barrels.
Link Posted: 10/1/2002 9:23:39 AM EST
Mr_h....My new Colt M4 16.5" barrel is a 1/7 and has a chrome bore and chamber, but is not marked as such (like they used to ). This is an MT6400.
Link Posted: 10/1/2002 9:30:51 AM EST
Boing, how did you verify the chrome lining? I've got tyhe same rifle and cannot tell. Is it because you now have the brake off?
Link Posted: 10/1/2002 9:45:10 AM EST
Colt only chrome lines the chambers AND barrels in their M4 barrels and their govt profile barrels. HBARs will have chrome lined chambers but not barrels. I dont remember when they started doing this, maybe someone who does will chime in. I'm thinking it was the mid 90's?
Link Posted: 10/1/2002 9:57:04 AM EST
See my post on the same subject on the Colt Industry board. Colt MTM6400Cs are all chromed, bore and chamber.
Link Posted: 10/1/2002 10:30:08 AM EST
anykey, A few things made me suspect it. First, rumor was that it would have a 1/9 twist bbl. but it came with a 1/7. With a Colt, to me anyway, that is a hint. Then, when cleaning after the first shooting session I wanted to look at the muzzle crown with one of those new-fangled (blue light) flashlights, and even looking through the brake there was a hint of what appeared to be the telltale chrome ring. Removing the brake verified it.
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