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Thread: ?????Chrome lined barrels are less accurate?????

  1. #21
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    A 10 MOA shooter using 4 MOA ammo worrying about 1/2 MOA differences between barrels is non-productive.

    Firing five-shot groups (yea, yea) I recorded ~1.5 MOA with a Spike's Tactical 16" M4 barrel and slightly better in a 16" BCM mid-length barrel both with 75 grain Black Hills ammo. I'm quite certain a better shooter with a stainless barrel, or even non-chrome-lined carbon steel barrel, could produce better groups. Group sizes with XM193 and various steel-cased ammo were double the size, and I doubt that the use of a "better" barrel would have done much for them.

  2. #22
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    Quote Originally Posted by rob_s View Post
    A 10 MOA shooter using 4 MOA ammo worrying about 1/2 MOA differences between barrels is non-productive.
    The other thing is though (and it drifts away from the topic of the thread a little) is the high end barrels tend to be more consistent as they heat up. Standard barrels will be more apt to suffer shifting POI under a high volume of fire. Consistency is also a big part of accuracy - certainly in my case it is more important to me than splitting hairs over MOA differences. It is a point often overlooked.
    Dan

  3. #23
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    My understanding is that chrome plating of the chamber and bore originated to make the barrels resistant to corrosion and help eliminate stuck cartridges in field & battle conditions for safety reasons. The very minor degradation in accuracy in combat would be inconsequential.

    Here's an interesting insight on the matter from Heckler & Koch on their new MR556A1:

    "Like the HK416, the MR556A1 uses a barrel produced by Heckler & Koch’s famous cold hammer forging process. But in a major departure from its HK416 lineage, the 16.5-inch MR556A1 barrel is not chrome-lined. By using the highest quality steel in the barrel manufacturing process, a long service life barrel that provides superior accuracy can be produced without chroming. According to HK engineers, chrome lining may add to barrel life but it does not contribute significantly to accuracy and can temporarily conceal defects in the barrel profile."

  4. #24
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    This is the rhetoric that RRA used when pimping their non-chrome-lined AR's. There is a link missing here, though, folks. What everyone does is compare a chrome-lined, non-match barrel to a match grade stainless barrel. Of course the stainless barrel is more accurate, but I suspect it has more to do with the conditions/tolerances under which it is produced, than the material (though the material may have some effect on repeatability.) The conclusion many try to draw from this is that chrome-lining is detrimental to accuracy, so, an un-chrome-lined chromoly barrel will be more accurate than a chrome-lined one. I have never seen any evidence to support this (all other manufacturing conditions held constant). Furthermore, it's not worth the tradeoff in reduced life/durability.
    Semper Paratus Certified AR15 Armorer

  5. #25
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    Quote Originally Posted by ASH556 View Post
    This is the rhetoric that RRA used when pimping their non-chrome-lined AR's. There is a link missing here, though, folks. What everyone does is compare a chrome-lined, non-match barrel to a match grade stainless barrel. Of course the stainless barrel is more accurate, but I suspect it has more to do with the conditions/tolerances under which it is produced, than the material (though the material may have some effect on repeatability.) The conclusion many try to draw from this is that chrome-lining is detrimental to accuracy, so, an un-chrome-lined chromoly barrel will be more accurate than a chrome-lined one. I have never seen any evidence to support this (all other manufacturing conditions held constant). Furthermore, it's not worth the tradeoff in reduced life/durability.
    Ash that is a very good point and you are absolutely right; it is not usually an apples to apples comparison that is made - there's definitely much more to a barrel than "chrome lined or not". However it still does hold that the chrome lining is *slightly* detrimental to accuracy - if it wasn't, the high power crowd et al would use it to get more mileage out of their barrels. The info is out there as to why this is so.

    But back to your point - I do believe that a super high end "match" type barrel with chrome lining would also outperform a run of the mill SS barrel due to the other factors you mentioned.
    Dan

  6. #26
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    The simple answer is yes. The bigger question is what are you going to do with the gun and will that difference effect your goal?

    I have some with chrome linings and some without. Chrome lining means more to me when firing full auto. I live in the dry desert, so I am not worried about rust. If I lived in an area with high humidity then chrome lined bores and chambers may be more important to me. My two "precision" ARs have stainless steel Lothar Walther barrels.

  7. #27
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    Not definitive by any means, but a test nonetheless. I was having this very discussion with a Marine 2112 armorer in the Quantico RTE shop one day, many years ago. He agreed to test one of the rifle teams M14 barrels, if I could get the plating done. I contacted a company that did such work, and arranged to have one barrel plated. The armorer then removed the barrel from one of the team's rifles, a rifle that had been tested very thoroughly in the test shed, and for which they had much data.
    To make this short, when the rifle was re-assembled with the plated barrel and then run through the same tests again, it was shown to be even more accurate than it was in the beginning. Now, this was a chrome-moly, match-grade barrel, which surely had a great deal to do with the results, but the armorer was still surprised. As far as I know, that is the only M14 the Corps ever had with a chrome-lined, match barrel, and I can tell you this. The team member who was issued that rifle wouldn't give it up.

  8. #28
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    Quote Originally Posted by M90A1 View Post
    Not definitive by any means, but a test nonetheless. I was having this very discussion with a Marine 2112 armorer in the Quantico RTE shop one day, many years ago. He agreed to test one of the rifle teams M14 barrels, if I could get the plating done. I contacted a company that did such work, and arranged to have one barrel plated. The armorer then removed the barrel from one of the team's rifles, a rifle that had been tested very thoroughly in the test shed, and for which they had much data.
    To make this short, when the rifle was re-assembled with the plated barrel and then run through the same tests again, it was shown to be even more accurate than it was in the beginning. Now, this was a chrome-moly, match-grade barrel, which surely had a great deal to do with the results, but the armorer was still surprised. As far as I know, that is the only M14 the Corps ever had with a chrome-lined, match barrel, and I can tell you this. The team member who was issued that rifle wouldn't give it up.
    Wait, you had an existing barrel chrome lined after the fact? and there weren't any signs of overpressure? What thickness was the chrome lining applied? Didn't this reduce the bore size by twice that thickness?

  9. #29
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    Quote Originally Posted by rob_s View Post
    A 10 MOA shooter using 4 MOA ammo worrying about 1/2 MOA differences between barrels is non-productive.
    Yes, but how many of us know a 10 MOA shooter who thinks his problem is a hardware issue not a software issue? The reason I can't shoot for shit has to be the gun!

    But then these are the same nimrods who will spend a ton of money to get a 1MOA gun and feed it imported wolf ammo because of the cost of decent ammo?
    Last edited by Beat Trash; 03-15-11 at 18:36.

  10. #30
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    Quote Originally Posted by rob_s View Post
    Wait, you had an existing barrel chrome lined after the fact? and there weren't any signs of overpressure? What thickness was the chrome lining applied? Didn't this reduce the bore size by twice that thickness?
    When I spoke with the company doing the bore, they said they had the capability of removing material from the bore to compensate for the thickness of the plating. The barrel was not air-gauged before and after, so I don't have an answer for your question of thickness. Signs of over-pressure? Don't really know, since I was not allowed to attend the testing. Didn't set off any alarms for the armorer or the people in the test shed, though, and RTE people are really thorough. This all happened almost twenty years ago, so a lot of the details have been lost to time. All I know is that it worked.

    As far as over-pressure goes, the same armorer talked the Corps into letting him take one of their match M14s to H.P. White Labs, to see what it would take to blow up an M14. At first, they used various rifle powders, and couldn't jam enough into a case to cause any damage. This didn't satisfy anybody, so they started using pistol powders. From what I remember, it finally took around 120,000 psi before the gun went kaboom. This was not done for fun - they actually needed to know how much an M14 could take before grenading. Competition was pretty stiff.

    This all came about because of the G2 and G3 loadings the armorers were using for long range, and they started to wonder about how much the rifles could really take. Couldn't have one blow up on the 1,000 yard line at Perry. How embarrassing!! Turned out that their "custom" loads were nowhere near dangerous.

    Ever hear about the two M14s that were built at Quantico to use Remington 30BR brass(didn't think so). The brass is no longer available, but it was extremely light, large powder capacity, and used small rifle primers. The armorer who did this designed his own custom reamer, and built two 14s using it. Those rifles would not accept M852 or Fed GMM, 'cause the chambers were too small. The final loading for the rifles, which were used solely for 1,000 yard matches, consisted of the old Sierra 180 gr Matchking, a CCI BR primer, and 44.5 gr. of IMR 4064 powder(pretty hot). It worked well enough to win the 1,000 yard Service Rifle matches at Perry the year they were built. There was some really fun stuff going on with 14s in those days.

    In addition, do you have any idea how many different sizes .308 barrels can really be? My Obermeyer Palma barrel has a bore and groove of .298 and .3065, respectively. A normal .30 cal match barrel would not be that small, even after plating. That hard chrome is really thin. Nobody was in any danger.
    Last edited by M90A1; 03-16-11 at 14:45. Reason: ETA & spelling

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