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Thread: "Heavy crimp and high bullet pull"

  1. #1
    Member rimfirematt's Avatar
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    Default "Heavy crimp and high bullet pull"

    Here is a instruction from Accurate powder.

    "Handgun loads using the slower powders (#7, #9 and 1680) require heavy crimp and High bullet pull to insure consistency- particularly with cast loads or extreme cold weather."

    What does high bullet pull mean?

  2. #2

    Default bullet pull

    It means that it takes more pressure to get the bullet to release from the case when the powder is ignited, allowing the powder to burn more completely and consistently. The heavy crimp helps make for higher bullet pull, as does tighter case to bullet tolerances.

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    Quote Originally Posted by rimfirematt View Post
    Here is a instruction from Accurate powder.

    "Handgun loads using the slower powders (#7, #9 and 1680) require heavy crimp and High bullet pull to insure consistency- particularly with cast loads or extreme cold weather."

    What does high bullet pull mean?
    There are several things that effect bullet pull. The technical term for that is rate of confinement. Just how snug does the bullet fit the case and bullet weight. Increasing rate of confinement is done by increasing bullet weight, using a tighter fitting case, usually done by using a smaller expander plug (.002"), using a bullet with longer bearing surface (longer shank) this is done by using a WFN desing vs a LFN design and lastly using a good crimp is part of high bullet pull and a case full of powder.

    Other things that effect rate of confinement are jamming the bullet into the lands of a rifle, or using smaller throats in a revolver. There are other things outside the handloaders control such as mechanical dimensions of the chamber that can effect it also.


    What we are trying to do here is give the most resistance to bullet movement so that pressure will build up quickly to the point where the powder will burn cleanly.

    There are some ALWAYS, things to do with certain types of powder, generally spherical powders, and these are:

    Fill the case with powder-Or as close to full as possible and stay with in safe charge weight.

    Use a heavy for caliber bullet-usually a hardcast, WFN design.

    Use a heavy crimp- I prefer the profile crimp as it is a combo taper and roll crimp.

    Use a tight bullet fit-This is smaller expander or .001" over sized bullet.

    Use magnum primers- This helps ignition but not rate of confinement.

    Remember this: Increasing bullet pull or increasing rate of confinement increases initial pressure of the fired round. Sometimes that is good sometimes it is bad.
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  4. #4
    Member rimfirematt's Avatar
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    Default

    Quote Originally Posted by Murphy View Post
    There are several things that effect bullet pull. The technical term for that is rate of confinement. Just how snug does the bullet fit the case and bullet weight. Increasing rate of confinement is done by increasing bullet weight, using a tighter fitting case, usually done by using a smaller expander plug (.002"), using a bullet with longer bearing surface (longer shank) this is done by using a WFN desing vs a LFN design and lastly using a good crimp is part of high bullet pull and a case full of powder.

    Other things that effect rate of confinement are jamming the bullet into the lands of a rifle, or using smaller throats in a revolver. There are other things outside the handloaders control such as mechanical dimensions of the chamber that can effect it also.


    What we are trying to do here is give the most resistance to bullet movement so that pressure will build up quickly to the point where the powder will burn cleanly.

    There are some ALWAYS, things to do with certain types of powder, generally spherical powders, and these are:

    Fill the case with powder-Or as close to full as possible and stay with in safe charge weight.

    Use a heavy for caliber bullet-usually a hardcast, WFN design.

    Use a heavy crimp- I prefer the profile crimp as it is a combo taper and roll crimp.

    Use a tight bullet fit-This is smaller expander or .001" over sized bullet.

    Use magnum primers- This helps ignition but not rate of confinement.

    Remember this: Increasing bullet pull or increasing rate of confinement increases initial pressure of the fired round. Sometimes that is good sometimes it is bad.

    Geez! who wants to buy 4#s of AA #9?!

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    Quote Originally Posted by rimfirematt View Post
    Geez! who wants to buy 4#s of AA #9?!

    It's not that bad. I didn't mean to scare you off.

    Those things are to get the most from that type of powder. The down side of it, if those things aren't followed would be;

    Inconsistant and inefficient ignition_Velocity will vary and accuracy may suffer.

    Possible incomplete ignition or squib load_ Which could leave a bullet stuck in the barrel or cylinder.

    Cold weather complicates these symptoms.

    Follow loading data and burn it.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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