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Thread: Taper or roll crimp semi auto rifle ammo?

  1. #11
    Member GuanoLoco's Avatar
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    Unless you are roll crimping in to a cannelure I seriously doubt that crimping is doing anything to reduce the likelyhood of bullet setback. 5pins has it right - it's all about neck tension. The Dillon size/TRIM (not crimp) die makes this a non-issue as the neck tension is crazy high.

    Here's a test. Measure cartridge OAL. Using both thumbs, press bullet against a piece of wood as hard as you can. Re-measure OAL. If it hasn't changed you should be good.
    Last edited by GuanoLoco; 01-21-2017 at 09:36 PM.
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  2. #12
    Member SecondsCount's Avatar
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    Quote Originally Posted by GuanoLoco View Post
    Unless you are roll crimping in to a cannelure I seriously doubt that crimping is doing anything to reduce the likelyhood of bullet setback. 5pins has it right - it's all about neck tension. The Dillon size/crimp die makes this a non-issue as the neck tension is crazy high.

    Here's a test. Measure cartridge OAL. Using both thumbs, press bullet against a piece of wood as hard as you can. Re-measure OAL. If it hasn't changed you should be good.
    I agree that neck tension is key but years ago I started putting a slight crimp on my AR loads that were loaded with a 55 V-max. It ended the setback issues I was having.
    -Seconds Count. Misses Don't-

  3. #13
    Member GuanoLoco's Avatar
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    What crimp die?
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  4. #14
    Member SecondsCount's Avatar
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    Quote Originally Posted by GuanoLoco View Post
    What crimp die?
    Dillon.
    -Seconds Count. Misses Don't-

  5. #15
    Member GuanoLoco's Avatar
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    I am guessing this works because the jacketing on a small diameter 223 bullet is relatively hard and/or the end of the case mouth is digging in to the bullet jacket. Given the relative springiness of a brass case I find it hard to believe that crimping is giving much compression benefit unless the case mouth is really loose to begin with.

    What size die, trim process and expander bit, if any, are you using?
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  6. #16
    I had malfunctions with a suppressed 5.55 SBR (like a fool, I forgot to bring different weighted buffers to fix this), and experienced bullet setback all of the way into the case with powder spilling, hence the OP.
    #RESIST

  7. #17
    Deadeye Dick Clusterfrack's Avatar
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    Quote Originally Posted by LittleLebowski View Post
    I'm trying to make up my mind on .223 AR ammo, I use a Lee FCD on my .300blk stuff.
    I don't crimp most of my rifle rounds, but the FCD does a good job.
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  8. #18
    Member SecondsCount's Avatar
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    Quote Originally Posted by GuanoLoco View Post
    I am guessing this works because the jacketing on a small diameter 223 bullet is relatively hard and/or the end of the case mouth is digging in to the bullet jacket. Given the relative springiness of a brass case I find it hard to believe that crimping is giving much compression benefit unless the case mouth is really loose to begin with.

    What size die, trim process and expander bit, if any, are you using?
    I assume you are asking me as you didn't quote my post.

    These days I use all Dillon dies but back when I was having an issue, about 25 years ago, I was using RCBS dies. Currently using the Possum Hollow trimmer but looking at an EZ trim or Giraud Triway.
    -Seconds Count. Misses Don't-

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