Extractor failure in XCR-L pistol - Page 2
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Thread: Extractor failure in XCR-L pistol

  1. #11
    XCR Guru Sean K.'s Avatar
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    Quote Originally Posted by Whole Bunches View Post
    Alex emailed me that his bbls are made of 4140 and are chrome lined and that chrome lining made a bigger difference in bbl life than nitriding.
    Which is counter to what the entire industry has found. Odd that in the XCR, nitriding isn't "as good" as chrome.
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  2. #12
    XCR Guru TexasChris's Avatar
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    Quote Originally Posted by Sean K. View Post
    Which is counter to what the entire industry has found. Odd that in the XCR, nitriding isn't "as good" as chrome.
    Yeah that's a little wonky....

    Bunchy, did Alex elaborate at all?
    Do what you've always done, get what you've always got. ----- Have gun. Will travel.

  3. #13
    XCR Guru navalbeaver's Avatar
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    Are you running suppressed? If not, RA needs to redo their gas port/dial sizes. It's not really adjustable if all you have is various states of over gassed.
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  5. #14
    Rifleman Whole Bunches's Avatar
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    I am not running suppressed in the 7.5" 5.56 upper. I did replace the A2 flash hider with a Kaw Valley linear comp to reduce the muzzle blast to the sides and the shooter. From my experience with a 10.x" AR 5.56 bbl Daniel Defense Mk18 upper, the Kaw Valley linear comp does increase back pressure. IIRC when I found failures to extract I contacted Kaw and was told indeed it increased back pressure. I then contacted several makers, with Midwest Ind saying their new Blast Master would not increase the back pressure. Indeed, installing that linear comp solved the extraction issue and tossed the blast forward...looks great too, not like any others available at that time. A2 flash hider and the Mk18 worked perfectly as it came from the factory. Kaw linear comp and the bolt would go back without extracting, I felt it was due to BCG going back before chamber pressure was reduced enough to allow extraction. Of course the DD upper is DI, whereas the RA is gas piston. There are now other linear comps that don't increase the back pressure, as the industry recognized linear comps could sometimes cause problems (and in other cases of too little gas, correct problems).

    I needed the gas set one or two higher (don't remember the specifics) during break in of the new bbl, but found I could later reduce it at about 50 rounds fired to where it is now. Of course the real test would be what gas setting with the linear comp removed. However I may not do that test as I'm happy with the performance now with the linear comp in place.

    Regarding chrome lined lasting longer than nitrided/nitrited/melonited/wasp/whatever the maker wants to call it: I've been keeping bbl wear records on the 300 Blackout for years. To that end, I have plain 4140, CHF 4140, 416R SS, chrome lined 4140, nitrided 4140, 4150/41V50/CMV (as I understand it, essentially the same steel with maybe slight variations depending upon what the bbl makers order) CHF nitrided, same with
    "double" chrome lining, same without CHF but with "regular" chrome lining bbls all chambered in 300 Blackout. Heck, I may have some other variations I don't remember at this instant unless I look them up.

    My regimen is shoot 5 shots (might be rapid for fun) and let cool to ambient temp before firing again. I have a bbl cooler and a fan I use (battery and 110 volt), trying to keep the heat even from bbl to bbl. From my real world measuring in the Blackout, plain 4140 wears the fastest. Using same bbl steel but nitride vs chrome lining, there is NO DOUBT in the way I fire that chrome lined is lasting longer from the standpoint of throat erosion (wearing away of the height of the lands nearest the chamber). There is no doubt that 4140 doesn't last as long as the 4150 types. There is no doubt that CHF 4140 is lasting longer than non CHF 4140, not a lot longer as in thousands of rounds longer, but longer non the less. 416R is lasting a little longer than plain 4140 (not a huge difference). The champion is a FN made CHF 4150 "double" chrome lined bbl. It is so slow wearing that I bought another one just to make sure. 2 problems: The more bbls, the less each gets fired, and I'm 70 years old, but having a lot of fun shooting at least twice per week.

    Here's four calculations (didn't feel like looking up and type all the data...it's feeding time for my goat herd). Dividing throat wear into 1" (US Military standard is 1" of throat wear means it's time to rebarrel for rifles below 50 caliber...or that was the standard when I was in...don't know about current standards; in wearing out 3 30/06 bbls, 1 inch throat wear meant in 250-500 more rounds the 100yd groups would rapidly go from inches to feet; in measuring a used M16 bbl, when the throat wear was at the reject line of the gage (1"), bullet were keyholing) and multiply times the rounds fired = bbl life. Of course this is not using accuracy or velocity reduction as a calculator, but TE wear is easy to measure and keep records of since my eyes are not good enough for repeatable accuracy testing and the US Military did it that way for decades.

    300 Blackout projected bbl life in a plain 4140 bbl until the TE is 1" = 11,820 jacketed rounds (Remington M700 bbl)

    300 Blackout projected bb life in a 4140 nitrided bbl until the TE is 1" = 13,697 jacketed rounds (Remington Micro7 bbl)

    300 Blackout projected bbl life in a 4140 chrome lined bbl until the TE is 1" = 16,740 jacketed rounds (RA XCR-L bbl)

    300 Blackout projected bbl life in a 4150 CHF double chrome lined until the TE is 1" = 22,667 jacketed rounds (FN bbl made for PSA)

    Note I said jacketed rounds. Shooting lead/cast bullets is giving a bbl life of about 3 times as much as plain 4140 steel with jacketed bullets.

    Note that my calculation assumes the throat wear will continue at the same slow rate throughout its life after break in. I don't know what will happen nearer the end of its life.

    OK, what Alex Robinson elaborated on. First he felt I should be measuring the changes in bore diameter in front of the gas block to the muzzle. I disagree; if the throat is worn out, the bbl is gone. After all, some shooters have cut the chamber end off worn bbls, rechambered and threading the bbl and keep on target shooting. Anyway, RA has done extensive testing using 7.62 NATO ball ammo and full auto fire, as they can't wait years for data. I'll let his words speak for themselves. He wrote more than that, but this is his bottom line. I have no idea if RA has throat erosion gages as I do. I was mainly interested in know the bbl steel and bore treatment that RA uses so I could know what category to put my RA bbls in. I appreciated his time in answering my question and in providing some RA obtained data as some companies refused to tell me anything, saying it was secret, for example: SIG. Besides RA, Ruger was another company that was very forthcoming, offering that if I wear out one of their Blackout bbls (I have 3 of them) they will rebarrel for free if they can have my data and section the bbl, keeping half and sending half back to me...of course I'll never wear one out, but still a nice gesture. I also found instances in which web sites listed incorrect bbl info. For example, Daniel Defense sent me a Blackout bbl with a tag saying it was chrome lined when they didn't make such a bbl at that time. I challenged them on that and was right; they subsequently corrected multiple DD internet pages, but at least they listened.

    "We tested Nitride against chrome on 4140 barrels. We shot 2500 rounds (all on Full Auto) through the each barrel. It took about 1.5 hours or each to get that round count. Military 7.62 NATO Ball was used. At the end of the test we could put a .307 gage pin down the nitrided barrel to the gas port. We could only put a .301 gage pin down the Chromed barrel. The chrome barrel held up significantly better. So much better that it took another 2500 round on full auto to wear down the chrome lined barrel to the point it matched the wear of the nitrided barrel.

    Unless your firing full auto only all the time, your chrome lined XCR-L .300 BLK barrel is going to last you a pretty long time. Nitriding barrels is not half as good. We've not only tried it on barrels but also other parts that are exposed to the barrel gasses. Chrome last much longer period!"

    I'm sure many of us have read on the Internet posting after posting claiming that nitriding is just as good as chrome or lasts longer than chrome. I feel the posts are simply people parroting what others have written without doing any testing themselves. Maybe if a cost factor or the use of less hazardness coating is considered, maybe someone could consider nitriding "just as good" as chrome, but I am going strictly by the wear I am measuring. I think the old days of "chrome lining is not even" are long gone. I know what I am seeing in my bbls! Now if any of my bbls no longer gives accuracy I am happy with, that will be considered.

    I am also keeping data on 5.56 bbls, but don't have as much as on the Blackout that I feel would be possible to post trends from at this time. In the case of 5.56 I have 2 bbls being fired full auto, but allowing cooling after each mag, so not a torture test. Most of the bbls are being fired 5 shots and let cool.

    Hope you find this of interest. My goats say they are starving!
    Last edited by Whole Bunches; 09-01-2018 at 05:42 PM.
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  6. #15
    XCR Guru TexasChris's Avatar
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    Very much so!!! Thank you sir!!
    Do what you've always done, get what you've always got. ----- Have gun. Will travel.

  7. #16
    XCR Guru navalbeaver's Avatar
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    Thanks the info. Very interesting. Is there a "good" vs "bad" nitride treatment? Anybody?

  8. #17
    Rifleman owtlaw's Avatar
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    Our Robinson team shooters wear barrels out between 10 and 15k rounds. Those are stainless barrels running .556

  9. #18
    XCR Guru Sean K.'s Avatar
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    Quote Originally Posted by navalbeaver View Post
    Thanks the info. Very interesting. Is there a "good" vs "bad" nitride treatment? Anybody?
    Supposedly there are differences. Case hardening (which is what nitriding a bbl is) can vary in depth and hardness. Most companies use a "proprietary" formula that can vary significantly from their competitors.

    It's a lot like induction and through hardening for axle shafts (for example). Each company has it's own formulation....and consequently, you get different results.
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  10. #19
    XCR Guru Sean K.'s Avatar
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    I beg to differ on chrome lining not being even, being "long gone"....unless you mean in the last 10 years or so. I got several RA bbls that were uneven and had to be honed to work correctly.

    Also...JFYI for anyone running into backpressure issues....most any baffled brake will increase backpressure. I have no experience with linear comps, but lots of experience with different brakes. The big benefit in SBRs is the increase in backpressure making them run a little more reliably in some instances.
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  11. #20
    Rifleman Whole Bunches's Avatar
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    Quote Originally Posted by Sean K. View Post
    I beg to differ on chrome lining not being even, being "long gone"....unless you mean in the last 10 years or so. I got several RA bbls that were uneven and had to be honed to work correctly.

    Also...JFYI for anyone running into backpressure issues....most any baffled brake will increase backpressure. I have no experience with linear comps, but lots of experience with different brakes. The big benefit in SBRs is the increase in backpressure making them run a little more reliably in some instances.
    Thank you for the post regarding uneven chrome lining. Time after time people say its uneven without giving any proof, in which case I felt from the words in their posts they were simply parroting old info. Here and there someone would say the state of the art in chrome lining has improved over the years. It is reminiscent of the fable about the blind men coming across an elephant for the first time and each describing what they feel the elephant looks like from each touching a different part...we are each reporting from our individual experience. I have sometimes wondered if the military way of gaging the throat to determine bbl serviceability is at least partially based upon the ease in which it can be done at even the smallest unit.

    I'm retired Navy, but did spend 2 tours with the Marines, the last of which I was made an alternate armorer and took the Marine course in inspection and repair of firearms. Besides the inspection points/criteria of various wear parts, the Marines also had a standard of how many rounds could be fired before the weapon was turned in for what they called 4th Echelon Maintenance (4th Echelon units replaced barrels for example) (my medical unit armory was 1st Echelon...basically we could tighten grips screws and inspect and that was all), regardless of whether the firearm appeared to be in working order. IIRC 50,000 for the M16 and 24,000 for the M14. Based upon my bbl wear measuring of M16 and M14 barrels, there is no way they could go that long.

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