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AR-15....to crimp, or not to crimp

Discussion in 'Reloading' started by utfelon, Aug 20, 2011.


  1. utfelon

    utfelon
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    I have a Stag super varmiter that I'm trying to load for. I'm new to the AR world. I'm loading some 65 gr SGK and not sure if a crimp is the way to go.
    Do you crimp some and not others? Do you crimp only one that have a cannular? I load for acc. so no crimp, or crimp for the set back.


    I've read both side or the fence and would like some detailed info.
     

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  2. crsuribe

    crsuribe
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    Yeah dude crimp them twice
     

  3. ColoCG

    ColoCG
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    I never crimp my .223 for my AR with hornady .55gr. fmj or sp never had a problem yet. Might depend on your gun. If you do crimp, crimp only bullets with a cannelure unless your using a LFCD for rifle. YMMV.
     
  4. PCJim

    PCJim
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    Have to agree with CG. I have used the LFCD and was not greatly impressed. Whether with or without cannelure, nowadays I don't crimp.
     
  5. Ferdinandd

    Ferdinandd
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    I asked the same question a while back and received conflicting opinions, but most folks said don't crimp. I was concerned about setback due to recoil. I loaded ammo without crimp. I measured the AOL of the rounds in the magazine as I worked my way through a 30-rounder. I had no detectable change in OAL. That was with 55 grain SP's over H335 of BLC-2.
     
  6. steve4102

    steve4102
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    From The Experts at Sierra.

    Neck Tension

    When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.

    There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra’s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra’s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition.

    To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.

    http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm
     
  7. utfelon

    utfelon
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    Thanx Steve good post
     
  8. EL_NinO619

    EL_NinO619
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    Light Crimp. Has worked great for me. Did not crimp 55gr sierras and did the set back test, and they moved for sure. not much, but i figure a crimp cant hurt for that crap case that has weak neck tension. Now if your shooting matches with a AR platform you may consider not crimping, but i just plink and have never had any less accurate ammo..
     
  9. steve4102

    steve4102
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    I have been doing a lot of load testing in my AR over the past several weeks. One of the tests was crimped loads vs non-crimped loads. Here is one of many targets that showed similar results. The target on the left was a 53gr Sierra Match with no crimp. The target on the right was same load same bullet with a med crimp using the Lee Factory Crimp Die.
    [​IMG]
     
  10. unclebob

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    If you want to increase the neck tension of the rifle rounds. Take about .002 off of the resizing button on the decapping rod.
    Or use the Redding bushing dies.
     
    #10 unclebob, Aug 21, 2011
    Last edited: Aug 21, 2011
  11. Zombie Steve

    Zombie Steve
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    <--- doesn't crimp for AR.
     
  12. steve4102

    steve4102
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    I've done that as well. I have several bushings for my 30-06 and 300WSM Redding dies. In my tests, increasing neck tension decreased accuracy while the use of the LFCD increased it, YMMV.
     
    #12 steve4102, Aug 22, 2011
    Last edited: Aug 22, 2011
  13. unclebob

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    Since I never really did get into high power shooting other than getting my feet wet. That was what I was told by many high powder shooters. And not to crimp the rounds. Both .223 and .308.
     
  14. DoctaGlockta

    DoctaGlockta
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    Light crimp here. Just another stage in the progressive so no big deal to do for me.
     
  15. nc910

    nc910
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    I don't crimp for any of my AR's.
     
  16. StoneDog

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    For those of you that don't crimp, have you ever had issues with the bullet falling into the case? I loaded up 50 a while back with no crimp. I accidentally slammed the ammo box on a table and a number of them dropped down into the case... I'm sure I did something else wrong, but I'm thinking the crimp would have prevented this.
     
  17. nc910

    nc910
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    StoneDog:

    I've never had any problems. It sounds like you seriously whacked your rounds without realizing it, or you've got neck tensions issues. Out of curiosity, what was the bullet/brass combination and what kind of seating die did you use?
     
  18. BBJones

    BBJones
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    No crimp here. I do pay close attention to neck tension. For those you crimp do you also carefully trim all your brass. Crimping without having the same length brass will yield very inconsistent crimps.

    The Sierra article was interesting that the OAL was increasing and not decreasing. Which to me is a good thing compared to the chance of the bullet being set back.
     
  19. jdavionic

    jdavionic
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    I always crimp my .223 rounds using Lee Factory Crimp.
     
  20. unclebob

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    You have something very severely wrong. Either you did not size the case, wrong bullets, wrong size bullets, worn out case, sizing die not adjusted right. Just to name a few.
    And no crimping the round would not have done anything. Unless you crimp in to the cannelure grove in the bullet if it has one. With the round being that lose I do not think that would have even helped.