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  1. #1
    mac37
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    Chamber Question

    I'm new to the Grendel. I just bought a Specialized Dynamics 20" .264 LBC upper. I was led to the LBC because I was told it would shoot both Grendel and 264 ammo. Anyway... I bought some Wolf and Hornady ammo from Alexander Arms. The upper functioned fine, shot all the Hornady ammo fine with descent accuracy but 2 to 3 rounds per box of the Wolf would not fire. They had light primer marks. I didn't think too much about it thinking it's just the Wolf ammo. Moving on I bought some AA brass (Lapua) and loaded some 120g SMK's. They won't fire just like the Wolf. I took some measurements with a comparator gauge and the Wolf and AA brass is shorter than the Hornady and much shorter than the fired brass. So, here's the question. Is my chamber cut wrong and is there any way to correct it? On a side note, the accuracy with once fired brass is much better than new ammo. Best preforming is 28g Vit 140, 120g SMK's in the Hornady brass with shoulders bumped back .002. Thanks for reading and any help is appreciated.
    Last edited by mac37; 11-27-2011 at 02:13 PM.

  2. #2
    RangerRick
    Guest
    If they had light firing pin indentations the bolt wasn't fully in battery. The brass probably needed the shoulders bumped back a little, but you may want to load one then eject it to check for rifling marks on the bullet.

    Any pressure signs on the fired brass?

    The Grendel chamber has a compound throat (starts at one angle then has a different angle the rest of the way). This was done to work with a wide range of bullets. The .264 throat has one angle and some throats are .295 and others are .300.

    The brass is identical for both but the LBC was designed for the Black Hills loads sold by Les Baer.

    If you reload you won't have any trouble once you get everything set up.

    You need to get an ammo gauge. Alexander Arms sells a nice one for $30. You can find it in their catalog under reloading accessories. If your sized brass or new rounds fit in it, it should chamber. If they fit in the gauge and won't chamber, you may have a chamber problem, but that would be unusual.

    When you say the fired brass is longer, exactly what length is it? Longer than the Alexander Arms spec of 1.526? See: http://alexanderarms.com/images/pdfs..._reloading.pdf

    RR
    Last edited by RangerRick; 11-26-2011 at 03:37 AM.

  3. #3
    mac37
    Guest
    I'm thinking you're right. It's not going into battery. The unfired round just falls out of the chamber.
    The extractor never picks up the rim of the case.
    No rounds fired had any pressure signs.
    Here are some measurements from the shoulders with a comparator gauge
    Hornady New 1.189, Fired 1.208
    Wolf New 1.181(will not fire), Fired rounds 1.207
    AA (Lapua) Brass 1.181 (will not fire)

    OAL of brass Hornady range 1.515 to 1.520
    AA (Lapua) 1.514 to 1.517

    I also measured the base of the case right above the rim and the rim

    Hornady Above .437, Rim .052
    AA (lapua) .439, Rim .058

    The rifle is supposed to have a 264 LBC Chamber but bolt is marked AA. I don't know if it makes a difference using an Alexander Arms bolt with a LBC chambered barrel?
    Last edited by mac37; 11-26-2011 at 04:54 PM. Reason: more info

  4. #4
    brickcues
    Guest
    The chamber on the 264 LBC AR has a neck that is .295, the Grendel is .300. The throat is also alittle tighter on the LBC AR. Wolf steel case ammo will not work with LBC AR as it measures .295 at the neck loaded and would be very tight to chamber. You can check the neck size by using calipers on the fired cases at the neck as their is suppost to be a .300 neck LBC AR also. The problems that I had with mine was that the 123 AMAX that I loaded at 2.26 were being jammed into the lands about .015 and the bolt would sometimes not close. When I reseated the bullets to 2.235 problems went away. Must check OAL to be sure bullets have about .010 jump.

  5. #5
    mac37
    Guest
    No, the loaded rounds are not jamming into the lands preventing the bolt to go into battery. When I load the 123g A-Max to the factory length, in the once fired/resized/shoulders bumped .002 Hornady brass, they fire just fine. If I use the new AA/Lapua brass the round won't fire. I can't get the bolt to close on empty AA/Lapua cases.

  6. #6
    Marksmanship Moderator
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    Quote Originally Posted by mac37 View Post
    I'm new to the Grendel. I just bought a Specialized Dynamics 20" .264 LBC upper. I was lead to the LBC because I was told it would shoot both Grendel and 264 ammo.
    Mac:

    Normally a guy needs to bump fired brass in order to get it to chamber. Since you are shooting factory loads, I doubt the problem involves the Lapua / AA or Wolf brass.

    Note that the all Hornady does with their brass is to change the headstamp between Grendel and .264 LBC. Just like you can buy Grendel brass with Lapua or Alexander Arms headstamps. The brass is identical in dimensions.

    The first run of Grendel brass that Hornady made had problems chambering in AA chambers because the brass was too long. Just like your current situation as you have found by measuring.

    Maybe who ever made your barrel cut the chamber long to accommodate this first run of Hornady brass? If they did, it is possible -- although I believe only very slightly -- that your AA and Wolf brass is so short that you are having problems with the firing pin hitting the primer hard enough to set it off.

    I say this because I have deliberately fired Grendel ammunition through chambers cut for the 7.62 X 39 brass while using the Grendel bolt -- thus creating excessive headspace. All rounds fired. Also, I have fired .308 ammunition out of 30-06 chambered rifles without any problems other than destroying the brass.

    Some of us never had a problem with this first run of Hornady brass but enough others did to make Hornady take note and subsequent lots of their brass has not shown any problems that have been brought to the attention of the Forum.

    Les Bear and Hornady both state very clearly that .264 LBC is interchangeable with Grendel brass.

    LR55
    Last edited by LR1955; 11-27-2011 at 02:44 PM.

  7. #7
    Moderator bwaites's Avatar
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    Quote Originally Posted by LR1955 View Post
    Mac:

    .......... Also note that if they state it is a neck diameter issue with AA using .300 and LB using .295, they are deliberately and willfully lying. AA marketed both chambers and factory loads will chamber and function perfectly with both.

    LR55
    This is splitting hairs a little bit, but according to Bill Alexander, AA never shipped any .295 necked rifles. CSS requested the .295 neck for some rifles and called it the "Match" chamber. Alexander felt that it compromised semi auto, and especially full auto, performance and thus refused to sell it under the AA brand. He also knew eventually there would be steel case ammo and that the .295 neck would be even more compromising. So AA didn't market he .295 neck. Bill Alexander has regretted ever drawing that chamber almost since day one because of the issues associated with it.
    ”You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live.” - John Galt

  8. #8
    mac37
    Guest
    LR55,
    I think you got it. It makes sense that the chamber is cut too deep. The Lapua case is set too deep in the chamber not only for the firing pin to reach but even for the extractor to pick up. As for the necks, all the fired cases measure between .298 and .300. So, it seems that the throat is .300 and the chamber is cut ~.008-.010 too deep. Could the AA bolt in an LBC chamber contribute to this? I read AA uses their own spec bolt and they will not work with other mfg's barrels and correctly headspace.

    Thanks for all the help!
    Last edited by mac37; 11-27-2011 at 05:44 PM. Reason: more info

  9. #9
    RangerRick
    Guest
    Quote Originally Posted by mac37 View Post
    LR55,
    I think you got it. It makes sense that the chamber is cut too deep. The Lapua case is set too deep in the chamber not only for the firing pin to reach but even for the extractor to pick up. As for the necks, all the fired cases measure between .298 and .300. So, it seems that the throat is .300 and the chamber is cut ~.008-.010 too deep. Could the AA bolt in an LBC chamber contribute to this? I read AA uses their own spec bolt and they will not work with other mfg's barrels and correctly headspace.

    Thanks for all the help!
    That's a dangerous gun. Did you buy it new from the manufacturer? If so send it back for a replacement. If they don't believe the problem and you want to confirm it, you can get a set of "go/no go" gauges. Midway sells them but they are out of stock there til the end of December: http://www.midwayusa.com/product/316...pc-264-lbc--ar

    Somebody else may have them in stock.

    Whoever you bought it from sold you a defective gun, so you should be able to get your money back.

    RR

  10. #10
    mac37
    Guest
    Yes, I bought it new from http://specializeddynamics.com/
    I've tried reaching him through another site but he hasn't responded. I'll let you know what he says when I hear from him.

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