I was wondering if the barrels on Colts civilian rifles like the MT6731 are chrome lined and if their chambers are 5.56mm or .223?

Welcome to the forum [:)]

The MT6731 is chambered for 5.56. As far as a chrome lined barrel I don't know. My new MT6400C is chrome lined but I don't know about the others.

According to the chart [url=http://www.ar15.com/forums/announcement.html?b=3&f=118&id=172]here[/url] Colt HBARs since 1997 have only been chamber chromed, but I've never seen any info aside from that chart.

Not chromed lined. Colt says it is a tad more accurate that way. Tougher to clean though.

Early 6731 uppers with preban features (except the bayo lug cuz that would be a 6721) have chrome-lined bore and chamber.  I don't have any knowledge about postban 6731 uppers and chrome lining.  

I bought one of Colt's conversion kits from KY Imports around 1995 and it came in a factory Colt box, marked as a conversion.  It came with the complete upper, two unblocked 20 round mags, special pin for adapting the upper to a large  hole lower, and instruction manual. The barrel is chrome-lined from chamber to muzzle and the upper has the extended M4 feedramps.

I think the whole thing cost around $550 and I wish I'd bought two of them.

Here's a question for a Colt RKI, were there any 6731 or 6721 uppers produced with a 1:7 twist and having the M4 feedramps?


Josh

Welcome to the forum! [beer]

Unfortunately, the only post-ban Colt with a chrome-lined barrel is the M4 Carbine, MT6400c.

Thanks for all of the replies.

CJan_NH,
     How do you like your MT6400C? Is it much louder with the muzzle brake. Is the brake easy to remove?

Again thanks everybody for the replies.

I like it a lot! It's a little louder than my two preban Colts but it's not a big deal. The brake comes off by punching out two solid pins that hold it on. When the AWB sunsets next year I'll thread the barrel and add a real A2 birdcage flashhider.

The Colt MT6731 I bought in 1997 had a chrome lined 16 inch barrel and a chrome lined chamber.