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Thread: Critical Failure - Seeking Advice

  1. #61
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    Take that barrel to someone with a true 5.56 finishing reamer and have them ream the camber, if it cuts some metal then it wasn't really 5.56 to begin with. Randall Rausch at AR15 barrells isknown to do this. I bet ADCO would do it as well. Maybe someone withsuch a reamer will volunteer to let you send it to them, free less shipping charges?

    "Addressing the problem of shootings by ban or confiscation of non-criminal's guns is like addressing the problem of rape by chopping off the Johnson of everyone who DIDN't rape anyone while not only leaving the rapists' equipment intact, but giving them free viagra to boot." --Me

  2. #62
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    Excellent. Now, what is your length from the base to this mark?


  3. #63
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    I measured 1.88" with my calipers.

  4. #64
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    Looks like you've got a .223 Remington chamber.

    Military 5.56 is a straight cylinder to 2.0026" (where your rifling land leade angle starts). .223 Remington leade angle starts at 1.8570". Look at the prints and compare.

    The good news is you can shoot commercial pressure ammo 'til the cows come home (some say 40,000 to 50,000 rounds!). A Melonite or salt nitride treatment will be hard and erosion-resistant for a long, long time.

    The bad news is the treatment makes the steel surface HARD (perhaps 70 Rockwell). If you stick a 5.56mm finishing reamer in the chamber you could possibly damage the reamer.

    Is this a dangerous condition? Only if you get an odd, over-pressure 5.56 cartridge.

  5. #65
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    Just to be sure, I will get a candle and try a couple more rounds to make 100% sure.

    If it is indeed a .223 chamber, than 5.56 ammo is unsafe - correct?

    If it is indeed .223, than I will be contacting AIM/Mossberg for some kind of resolution.... I have thousands of rounds of 5.56 and want to be able to safely shoot it in this rifle build.

  6. #66
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    Sounds like a winning plan!

    If it wan't Melonited, nitrided, Hard-Blued, or whatever they call a hardened-treated steel I'd probably say forget about it -- but as it won't show much erosion and wear for a few tens of thousands of dollars worth of ammo I'd ask for a 5.56 throat.

  7. #67
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    Just so I'm clear in this... If it is .223 chamber, then is shooting commercial 5.56mm unsafe?

    Thank you Sir for all of your knowledge and help!

  8. #68
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    It was my understanding that with a 5.56 leade, short bullets like 55 grainers, or anything loaded to mag length if considering reloads, would always be a few thousandths off the lands. Is it possible that dropping a marked bullet into a 5.56 chamber would produce no marks at all?
    B.A.S. Mechanical Engineering Technology

  9. #69
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    Quote Originally Posted by awpk03s View Post
    Just so I'm clear in this... If it is .223 chamber, then is shooting commercial 5.56mm unsafe?
    5.56 military ammunition loaded to MIL-C-63989 (for M855) and MIL-C-9963 (for M193) are loaded hotter, to higher pressures, than SAAMI .223 Remington. They are meant to be fired in military chambers reamed for 5.56mm (with the extra freebore).

    Prvi Partizan loads to CIP standard for 5.56 and is ISO quality-control certified:
    In 1998, PPU was the first producer of Serbian Defense Industry, which gained certificate of Quality System conformity with requirements of standard ISO 9001:1994.

    PPU is just finished activities on recertification of Quality Management System according to standard ISO 9001:2008.
    A .223 throat will raise pressure. A barrel surface-hardened (a harder steel or treatment) will do you no favors.

    Add a case with any anomoly (perhaps a thin wall and an off-center flash hole), or maybe a pushed-back bullet and gap between the end of the barrel and the face of the bolt lugs and you increase risk of a kaBoom.

    Your personal rifle or carbine is designed and supposed to be built with a certain safety factor. We have pages and pages of specs and standards. Shaving off that factor is not prudent.

    I'd REALLY be curious to see how your bolt would handle a GI proof round with this throat.

    Look at the photos of your extractor. When the gas blew out of the base of the case it followed the extractor channel and bent the front of the extractor with lug up and into the barrel extension.

    The M16/M4 is a good, solid design, but they also have a history of kabooms for unknown reasons. You have a reasonable idea how your particular carbine is built.

    -----

    As for the lands marking the bullet ogive, the absolute best way to determine whether the bullet touches the lands (or not) is to use an actual bullet and a Stoney Point gage. You'll feel when the bullet touches the lands, and you can mic the distance to the marks:


  10. #70
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    Critical Failure - Seeking Advice

    Quote Originally Posted by awpk03s View Post
    Just so I'm clear in this... If it is .223 chamber, then is shooting commercial 5.56mm unsafe?

    Thank you Sir for all of your knowledge and help!
    I'm putting that gauge in the mail to you tmrw FYI. But it sounds like you've confirmed.


    Sent from my iPhone using Tapatalk 2

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