Attention men....newbie on board. I just sprung for a new Rock river CAR4 16" flattop with 1:9 chome-moly barrel and I  have a couple of questions.
 First off, I spent 6 yrs in the Army so I am familiar with the weapon and maintainence procedures but I have some confusion concerning the  barrel. Is the bore on this piece chrome lined? It is the shiniest, smoothest easy to clean bore  of all my rifles but because of the flash hider I cannot get a close look.  Can someone explain the difference between chrome-moly, and chrome lined?
 Next during break-in I tried a number of  different weight  and style bullets, including Santa Barbara 62 GR SS-109, Win 55 gr fmj, Win 62 gr FMJ, South African 55 gr FMJ, and even black Hills 68 Gr  BTHP with mediocre results as far as accuracy. I got 1.5-2.0 MOA with the above listed ammo with the Black Hills being the best.  Can I expect this to get better after break-in?
 I also had several failure to feed instances where the bolt hung up half way in it's travel to lockup, though the round chambered due to inertia. This was not because of bad ammo, as if I elevated the muzzle the round would slide out of the chamber to meet the bolt in it's stuck position. This required considerable force on the charging handle to un-stick the bolt . I dis-assembled and inspected the bolt carrier and found a couple of small machining burrs on the leading edge of the bolt carrier where the grooves were milled to ride in the receiver. After  200 or so rounds the FTF thing stopped on it's own and I noticed the machining burrs were gone when I last cleaned and inspected. My question is if this kind of stoppage normal during break-in .  Also is this kind of accuracy normal using the kinds of ammo noted above?
 Some 69 Gr SMK loads I assembled provided sub MOA results. I thought a good rifle would digest about anything with decent accuracy. I am stuck handloading for the MOA claim RR gives? Or am I being too critical for performance from a 16" carbine? I have to say it is a really solid looking piece of machinery, and now that it has loosened up some I am looking forward to sending as much in-expensive/surplus ammo downrange as budget will allow. I am now pretty darn happy with this peice since the FTF thing has resolved itself and since the SMK loads are doing as well as they have been. Comments anyone?

dupe

this was the complete thread

Hello and welcome to the board...

With a clean bore the chrome bore will look a bit frosty as opposed to the plain barrel which should look bright and shiny... It is industrial hard chrome, so it won't shine like decorative chrome plating... What are the barrel markings? They might be able to tell you if its chrome or not...

1.5-2.0 MOA isn't that bad, I bet a little more range time would improve it...

Its hard for any one to say what was causing your FTF trouble... Did you clean and lube the rifle before shooting the first time? It probably was due to it being new and tight since it loosened up and corrected its self after a couple hundred rounds were put through it...

The markings on RRA's barrels are under the gas tube, on top of the chamber, on the barrel.

What letters (and what number) is there?

WIZZO

WIZZO...the barrel markings are N9C...Them handguards are a BITCH to remove and re-install alone.  I ordered 1:9 twist chrome-moly. The bore cleans like chrome lined.  What can you tell me?

WIZZO...the barrel markings are N9C...Them handguards are a BITCH to remove and re-install alone.  I ordered 1:9 twist chrome-moly. The bore cleans like chrome lined.  What can you tell me?

Quoted: WIZZO...the barrel markings are N9C...Them handguards are a BITCH to remove and re-install alone.  I ordered 1:9 twist chrome-moly. The bore cleans like chrome lined.  What can you tell me?

N = NATO 5.56 chamber
9 = 1/9 twist
C = chrome lined

Yep, theshootersden, got it.

This would probably be why it's cleaning up so easily.

WIZZO

BTW, 2MOA is generally the accepted accuracy to get from Mil-spec ammo. The more expensive 75gr stuff will most likely yield the most accuracy out of the 1/9 barrel from what everyone on here says.

Thanks Shooters Den.   I thought the barrel cleaned up awful easy. On the RR website the barrel options are chrome-moly, chrome lined and stainless steel. I didn't pay for chrome lined, is there a difference between chrome moly and chrome lined? Is the chamber on this thing also chrome lined? Did I get a freebie? or am I still not getting it?

You might not have paid for chrome-lining, but you certainly got it.

My RRA 20" is marked W9A
W=Wylde chamber
9=1/9 twist
A=Chrome-moly barrel

You definitely got a chrome-lined barrel. It will last onger (about twice as much, upwards of around 25,000rds) and it will be easier to clean (as you've already experienced)

Yes, it will have a chrome-lined chamber.

WIZZO

Thanks WIZZO.  That is a $40.00 freebie. Plus I have found that it loves 69 gr SMK/25 gr of varget. Have yet to chrono the load but will before winter hits, assuming my OT at work slows down. Gotta love them RR guys! Thanks for clearing up my confusion.   ;o)

Thanks WIZZO... That's a $40.00 option . I'm OK with that as it loves 69 GR SMK/25 GR Varget. Havn't chrono'd the load yet but will lwhen work OT slows down.  

FWIW - I tossed together some half assed 69 SMK loads the other day - Mil brass, cleaned swaged - no trimming, no primer pock uniforming or flash hole work, stuffed 23.5 of H335, a Fed GM primer, and a 69 SMK - 1/2 MOA out of a cheap assed DPMS 16" tube.

H335 metered well out of my Dillon.


Good luck

i payed for a rra m4 upper from adco they sent me a n9c when i didnt pick the option of a chrome lined. i was thinking they where sending me a chrome moly but i got a chromed i guess so im ultra happy.  m4 feed ramp suck on it though cuz they wernt paid much attention