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Thread: roll crimp vs taper crimp "technical question"

  1. #1
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    roll crimp vs taper crimp "technical question"

    I've read enough to know the different applications of roll vs taper crimps, however, I am (without sounding dumb) still lost as to how to spot the difference. I mean, a heavy taper crimp will look just like a roll crimp, right? I've been using Lee dies all this time, thinking that, say, my .357Mag dies (seating/crimping die) applied taper crimp. Today I got to use, for the first time, the Lee Factory Crimp die, which is supposedly a roll crimp die, and the crimp looks just like the crimp from the seating die.

    How does one tell the difference, or what difference is there to the internal crimping surface?

  2. #2
    My understanding is this..
    The cast lead bullets I shoot have a crimp groove,and the crimp 'rolls' into that groove.
    Jacketed bullets have no such groove,the the crimp die is tightened just enough to squeeze the casing against the sides of the bullet,called 'taper crimping',which follows the tapered side of the bullet.
    To me,a rol and taper crimp look entirely different.

  3. #3
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    Unless specified as a taper crimp, Lee revolver dies will roll crimp. As well as most other manufacturers versions of revolver caliber dies. Auto dies will 'mostly' have taper crimping ability now a days. Except 45 auto which I have seen with roll crimper in some makes.

    Taper crimped cases, properly done, don't have a visible crimp. The crimp is long and gentle and without radius...hence the 'taper'. If you look into the crimp die, the roll version will have an obvious restriction that contacts the mouth and forces it inward. The taper die isn't so obvious and may look like it has no crimping ability at all.

    The FCD makes what looks like a heavy roll crimp on revolver cases, but it does it by squeezing the mouth rather than ramming the mouth into a restriction. I like the FCD in revolvers especially as it isn't so dependent on case length to make a good and consistent crimp. It works more like a collet crimp if my memory serves.....been a while since loading any revolver ammo.

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    Recoil Rob is partially right here.

    For years ALL dies with built in crimp shoulders were roll crimp dies, revolver or semi-auto case didn't matter, they were ALL roll crimp.

    Then the taper crimp dies came out, mostly after people started trying to do strange things with auto pistol cartridges for IPSC and they got the roll crimp set so deep the cartridge did not headspace and they had misfire problems.

    This was pure stupidity, I have loaded hundreds of thousands of .45 ACP with a seating die with a roll crimp in it. I NEVER had one case fail to headspace and fire and that included with M1917 revolvers fired with no moon clips and even an old Command Arms carbine.

    After that taper crimp dies were special and had to be bought and used separately. They came after carbide dies became common but before the price differential dropped to the relation to steel dies it is today. The carbide dies used to be MUCH more expensive because the carbide was so much harder for the die manufacturer to work with.

    Then, some manufacturers would let you order the dies with EITHER crimp type you specified. This caused problems because a dealer would have a roll crimp die set in stock and the customer would want a taper crimp set and the dealer would have to order a whole new set and still have the old set in stock.

    Lately they have tried to match the crimp type to the cartridge type.

    I don't have any taper crimp dies, my sets are older than that or purchased with the roll crimp option. If I want a serious crimp I use the Lee Factory Crimp die.

    Buckshot

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    Thanks, this means then that I've been roll crimping all along with my revolver dies as they are of new production, and that's why I am not seeing any difference between the crimp made by my seating die vs the one made by the FCD.
    A while ago I asked a dealer here whether the dies made roll or taper, and he said taper. That's why I was under the assumption that I've been taper crimping all along. Well, learning something new every day.
    Makes sense what Buckshot said. My .40 and .45acp dies do not crimp the same way, although I never tried to apply a heavy crimp since the headspace issue.
    Thanks for the explanation.

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    roll crimp

    buckshot is right on:and gave the best answer I have seen.on my 45 acp I leave the bullet out and crimp on first band 1/32 down.I have never had a jam or failure to feed.to much is made of the head space.the 1911 will hold the brass against the breach face.

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    I have several .44 mag revolvers, plus a .44 mag lever rifle and a .444 Marlin lever rifle. Accordingly, much of my reloading is with the LBT design cast bullets. SWC designs will not reliably feed from the magazines of Marlin lever rifles. The LBT bullets have a smooth ogive with a generous meplat or tip and feed smoothly.

    Most of the time, the 1.6" OAL needed for my rifles doesn't line up with the crimp grooves on these bullets, so I use a separate taper crimp die, or "factory crimp" die as Lee calls the .444 model. These bullets, crimped this way, feed just fine in the rifles and are more than adequate for medium intensity .44 mag loads in the revolvers. However, for heavy 300 grain loads in my Dan Wesson M44, I prefer a heavy roll crimp over the shoulder of a SWC bullet, the slower powders need the extra time to develop pressure. - CW

    http://www.beartoothbullets.com/
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  8. #8
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    "...how to spot the difference..." Case mouth on a roll crimp is rounded. A taper crimp is not.

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    They say a picture is worth a thousand words...on the left a roll crimped 45 Colt, on the right a taper crimped 45 ACP. On the Colt you can see the brass actually rolls into the cannelure. Now as the APC actually headspaces on the case it cannot be roll crimped, same goes for most non-bottle neck semi auto cartridges.

    Last edited by Absintheur; December 29th, 2009 at 08:31 AM.
    But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security. - The Declaration of Independance

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    How does one tell the difference,
    A thermos keeps things hot or cold, how does it know

  11. #11
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    How does one tell the difference,

    A thermos keeps things hot or cold, how does it know
    Yeah, very funny. If you haven't noticed, I stated that my initial confusion came about when a veteran reloader and a FFL told me that all seating dies only taper crimped. Okay, maybe he was coming from an era when that might have been true, but since then it was explained that revolver dies roll crimp and semi-auto dies taper crimp.

    One could see then why I posted this question, after loading thousands with the seating die only (assumed to be a taper, but not really), and then switching to a FCD (assumed to be a roll), and why I did not see any difference in the crimp profile.
    That does not mean that I am dumb or ignorant, just that I was given some wrong info early on and never had an opportunity to dispute it.

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    Don't feel bad Henry... I have run across a lot of "knowledgable" people over the years who knew something different than was completely accurate....

    One of the things I have observed, and one of the reasons I frequent boards and read more than one, is that people focus in on there interests and know them and little else. I belonged to a bullseye group for awhile that was 99% 45 ACP and I was one of two revolver shooters.
    Paul
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  13. #13
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    All Lee dies taper then roll in the standard seating die. FCD will do the correct one for the caliber loaded. Read about dies here. http://www.leeprecision.com/cgi/faq/index.cgi

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    Absintheur,

    With some careful adjustment of the roll crimp die and case selection for the same length, I can reproduce the look you have posted for the taper crimp with a roll crimp die, did it for years and still do it often.

    Buckshot

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    Lee Seating Dies have a Modified Crimp + FCD

    From Lees website
    Seating die crimp style

    There are two crimp shoulders in our bullet seating dies. The first shoulder applies a slight taper crimp and the second shoulder applies a full roll crimp. The closer the die is adjusted to the shell holder the heavier the crimp will be.
    The factory crimp die (FCD HANDGUNS) has this to say >
    The type of crimp on the die depends upon the type of cartridge. With cases that headspace on the case mouth such as the 45ACP, the die essentially reduces the outer diameter of the case mouth into the bullet. On other cases, a roll crimp is applied.
    NOTE: The FCD is different for a Rifle. Lee Tech Assistant http://www.leeprecision.com/cgi/faq/index.cgi
    Last edited by 243winxb; December 30th, 2009 at 11:02 AM. Reason: added link to Lee Tech Assistant.

  16. #16
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    IMO This round is over crimped, brass life will be short.

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    IMO with a 260 grain bullet and a stout load at 850fps any less crimp and this bullet will pull...actually that is not opinion it is fact...lol. This is not a load I shoot a great deal of but it is very effective on deer. I used this as it is the most exaggerated roll crimp I had on hand.
    But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security. - The Declaration of Independance

  18. #18
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    Good crimp thread here, many photos, have a look.(ORG Site) http://www.thehighroad.org/showthread.php?t=469815

  19. #19
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    crimp

    the 45acp does not have a crimp with jacket bullets.every target shooter I know used a roll crimp on 45acp as I do.there was no taper crimp until recently.I would say in the 1980s.I use SWC in my pistols except for the 38. where I use WC.I have a revolver and a S&W 52.my win trapper feeds SWC
    45 colt fine.I have no idea what the OAL is.I load it like I do my ruger black hawk.

  20. #20

    taper crimp

    If you want to experiment with taper crimping:
    Remove the sizing dies primer decaping stim. Then readjust the die for crimping. It works!

  21. #21
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    Absintheur, is that .45 Colt crimp from a Redding Profile Crimp die? It looks just like the crimp the Redding die puts on my .44 Magnum loads.

    Everybody talks about "taper" and "roll" crimps, but I've found the Profile crimp to be a subtly different animal.
    "Ya gotta be tough if you're gonna be stupid."

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