RELOADING FOR AN AR--.308 NON Crimp?

Discussion in 'Reloading' started by bigbuck, Mar 30, 2013.

  1. bigbuck

    bigbuck Well-Known Member

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    I will be loading for an AR .308 shortly and I need to know if I can do it without crimping ? I just shot some non crimped factory Ammo out of it and it shot fine with two different kinds of Ammo. I want to load up some Accurate loads so in my opinion crimping would not be in the right direction what say you ?
    Thanks for looking....
     
  2. Sgt45

    Sgt45 New Member

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    I don't crimp in my .308 and I haven't had a problem yet (other than loose scope mount and loose turret which turned all my groups to garbage).
     

  3. SidecarFlip

    SidecarFlip Well-Known Member

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    Rule of thumb is:

    If the projectile (bullet to you) has a crimp cannelure and you are magazine loading in a high recoil firearm, it's advisable to crimp the case mouth intoi the cannelure so the projectile don't move during recoil........

    or in the case of select fire weapons, the multiple recoils of automatic fire can move the projectiles in the case mouths, hence they are crimped (case mouth) and the primers are crimped (the edge of the case head is rolled a bit inward.

    Having said that, I crimp all my loads, be it a cannelured projectile or not. However, excessive crimping an non-cannelure projectile can lead to excessive case pressure as well as work hardened brass so I don't advise crimping for anyone unless necessary (and the projectile has a cannelure).

    I use specific made crimp dies that are normally not used everyday btw.

    Typically, OFMB cases will have been crimped and primers locked and sealed in both 5.56 NATO and 308 7.62x51? NATO.
     
  4. bigbuck

    bigbuck Well-Known Member

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    OFMB Cases . What does OFMB stand for ?
    I plan on shooting sierra 175 SMK's or Bergers they dont have a cannelure on them . Does the Military crimp there .308 SASS Ammo ? Thanks
     
  5. SidecarFlip

    SidecarFlip Well-Known Member

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    You need to get with the nomenclature...

    OFMB= One Fired Military Brass

    No, neither the Berger or the Sierra have a cannelure and every loaded round the military uses in normal procedures, is crimped, both at the case neck and the primer pocket.

    So, you are going to load Sierra 175 grain SMK's or Bergers in the same flavor, I have to ask, what propellant, what primer what propellant load and seating depth and I presume you will full length resize the cases, or maybe not.....

    One thing in your favor is that modern firearms have a hole on each side of the receiver in case the shooter makes a mistake... Those holes let the fire out instead of blowing back in your face..... Great innovation.:)
     
  6. bigbuck

    bigbuck Well-Known Member

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    I will be loading for a AR DPMS .308 Auto. I planned on using federal 210 Primers with Varget or RL -15 powder. What I usually do with my bolt guns is seat the bullet where it will just barely clear the mag well. I am a little hesitant to do that with my AR as I am new to this type of rifle . I have .308 winchester load data in several of my loading manuals. I thought surely that the US Military snipers that shoot the .308 semi Auto would have special Ammo (Match) . Do you know exactly what they use ? and how it is loaded ?
    Thanks
     
  7. jlamb

    jlamb Well-Known Member

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    I load for a DPMS AP4 in .308. I haven't used a crimp yet but have purchased the Taper Crimp die set. I've found on my 5.56 that the crimp is making a difference. I think the bullet is moving when the cartridge is slammed into battery. I'm also using it on match bullets w/o a canelure.

    I have under .5MOA performance with 150SMK's and 44.5 grains of Varget.
     
  8. SidecarFlip

    SidecarFlip Well-Known Member

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    .....be apprised that applying a crimp to a non-cannelured projectile (I dislike the word bullet btw), (it's a projectile...) can cause overpressure because it restricts the initial movement of the projectile as it exits the case.

    Consequently, applying a crimp is an exercise in experience and caution. Too much equals an overpressure condition and it workhardens the brass prematurely and we all know how hard brass is to get right now. Workhardened necks will crack prematurely and the casing at that point is scrap.

    Too little does nothing. I use caliber specific Lee Collet Crimp dies (only Lee dies I use btw), and a deft hand at applying the crimp. I don't care for or employ a roll crimp on any rifle die. All my pistol dies crimp but pistol brass is all straight walled, not bottleneck.
     
  9. bigbuck

    bigbuck Well-Known Member

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    Thanks for the load data . Whats your OAL on the .308 rounds ?
     
  10. bigbuck

    bigbuck Well-Known Member

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    My father has loaded for several of his pistols . I will get him to help me out with the crimping . He will love to show me how to do it and rub it in of course:)
     
  11. jlamb

    jlamb Well-Known Member

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    The COAL is 2.800". I've found Sierra 150SMKs and 150gr Hornady BTSP to work the best.