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Thread: Can a round be over crimped??

  1. #1

    Can a round be over crimped??

    I've just bought. 30-30 crimp die and have crimped 10 rounds tonight, I am using a lee hand press and I run the press up and when the shell holder contacts the die bottom, there is about 1" of travel left so I pushed until the handle ran out of travel, there was reasonable force but nothing too substantial.

    the crimps are about 1mm long and the case neck OD measures .327" and the crimped section .317"

    does this seem ok? Is it possible to overcrimp and if so would this lead to anything dangerous?

    The three rounds show 2 crimped and 1 before crimping.

    GixerAttachment 50976Attachment 50977Attachment 50978

  2. #2
    They look good to me. My understanding is that Lee regard .004'' as a tight crimp so the .010'' may be a bit tight ? If you look on YouTube there is a good demo of setting the Lee Factory Crimp Die, using a piece of paper as a shim between the petals. The die can only crimp until the petals close, which is where I set mine on the .243.
    Hopefully Muir will be along with a more informed answer soon, but do have a look at YouTube in the meantime.
    A pessimist is an optimist with experience.

  3. #3
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    Yes. Rounds can be over crimped. This might in extreme put a distinct "waist" on the bullet so it is no longer straight sided at that point. Over crimping shortens case life as it work hardens that part of the case. Also possibly causes case stretching and will increase velocity and pressure. In theory however velocity over a series of all the same degree of over crimping...on say five rounds will be more consistent.

    Is it dangerous? In pistol calibres possibly. But in sensible rifle reloads it shouldn't ever be possible...with sensible powder charges...for merely over crimping to cause dangerous pressure. High pressure, yes, very high. But unless you loading is already loaded right to the limit of pressure in uncrimped cases then no.

    More harmful would be loads where the bullet is seated so far out that it engage the rifling when chambered. I would say that in 30-30 it shouldn't be possible to overcrimp such that dangerous pressures are created if your loadings are using sensible powder charges as per the manuals. As this is an old cartridge where most manuals give loadings of only modest pressures.

    Depends however on the age of your rifle and its design and headspace with this being a rimmed round may give case stretching issues. This may give case head separation issues in subsequent reloads if the headspace isn't addresses in the cartridge cases when reloaded again and the dies left unadjusted.
    Last edited by enfieldspares; 03-01-2015 at 12:07.

  4. #4
    With a Lee FC Die adjustment of crimp is easy and once the crimp is at max. and the 'petals' fully closed, no further crimp is obtainable...

    What you appear to have done doesn't seem unreasonable as a first attempt but I'd guess you can back off the die and the crimp will still both hold the bullet and give consistent neck tension. Just follow the die instructions.

    Dangerous - unlikely. Shorten case life - not in my experience. The crimp is often trimmed away when cases are trimmed besides, you can always anneal the cases. ATB
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Schmidt & Bender 8x56, 110gn Nosler Accubond = Game Over!

  5. #5
    should be fine
    I have overcrimped several loads
    never had one spike in pressure and some of the ones I have pulled have left a distinct waist in the bullet bearing surface
    Think about the driving bands on some bullets and that in itself is not going to be an issue

    what you may find is that the lip of the neck post firing still looks to display a crimp to it
    what you have is a thinner section at the mouth/lip where the roll crimp has squeezed brass down towards the shoulder slightly
    this can cause a sticky chambering as you have a very slightly thicker section.

    simple answer is to get a factory crimp die
    more controllable, crimps in a perpendicular linear direction and avoids many of the pitfalls of roll crimping

    Quote Originally Posted by deeangeo View Post
    With a Lee FC Die adjustment of crimp is easy and once the crimp is at max. and the 'petals' fully closed, no further crimp is obtainable...
    but the controlling factor here is neck thickness not crimp depth
    you need consistent neck thickness and case length to rely on the collet closing limit

  6. #6
    Did you crimp those rounds with a Factory Crimp Die? Or the seater die? And if the seater die, did you seat and crimp at the same time??

    As to over crimp. My buddy and I pulled some rounds from factory 338 Lapua. The crimp was so severe that we looked under a magnifier to see if it had cut through the jacket. All were the same. All of the remaining ammo beat up the 24" gong at 1680 yards.~Muir

  7. #7
    Thanks for the input folks, it's a factory crimp die Muir.


  8. #8

  9. #9
    No sir....its once fired, is this another 30-30 idiosyncrasy?

  10. #10
    No. It's just a good practice. Lee says it's not necessary with the FCD but I think you'd get a neater result if you trimmed your cases. I don't consider crimping an option unless I have cases trimmed to the same length. In your case, I could tell by looking at the pic that you hadn't.~Muir

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