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  1. #21
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    Default Re: Shotgun ammo crimp

    Sorry, late to the thread.

    I find from my own experience it has a lot to do with the type of load one is making and your press. For instance, on my load-All 2, Lee designed the system to use spent trap hulls (I tend to stick with high brass for Hulls for slugs and buck) for loading. The press does not crimp spent S&B Comp Slug and Industrial cartridge LG hulls very well due to the thickness of the hull material, that being in star crimp form. Therefore I find that thicker hull case materials should be re-crimped in roll format.

    In terms of the type of loading, using a standard 32 gram trap wad and 67.5 mm Hull with a star crimp gives you enough room for 6 "double ought"/.33 caliber buck shot balls stacked 3 high in the wad, these are my typical loads, as per Lee instruction and work fine for my intended purpose. However, if an 8-9 pellet "double ought" or 6 pellet "triple ought"/0.36" shot load is required, a roll crimp with a shot cup is more appropriate to accommodate the extra length of the load especially if you are chamber limited to 2.75" shells.

  2. #22
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    Default Re: Shotgun ammo crimp

    Quote Originally Posted by Pirate View Post
    Thanks guys, my curiosity is generally satisfied...

    Would roll-crimped ammo not allow "longer" cartriges, because the chamber does not need to accommodate the extra length of the unfolded star crimp?
    Most of what I said in my previous post applies to double barrel guns, as does most of what follows below. (And yes, I'm going off track a bit, beyond the scope of the original question)

    Older shotguns had a relatively abrupt change in diameter just in front of the chamber, so one might have been able to fit a longer cartridge in there if it was roll crimped. They also often had shorter chambers - 65mm was quite common and sometimes even shorter. More modern guns however have a more gradual taper in front of the chamber and anyway tend to be chambered for longer (70mm or even 75mm) cartridges so it doesn't make any practical difference with a modern gun.

    Yes, roll crimped ammo does allow for longer cartridges.

    One also needs to be aware that shotgun cartridge length measurements as stated on the box refer to the length of the cartridge AFTER firing ie once open and are a bit nominal anyway and once again vary between manufacturers. An unfired roll crimped cartridge marked 70mm has an actual length around 62-63mm while an unfired star crimped cartridge is around 58-60mm. Both would probably physically fit into a chamber on an old gun marked 65mm, but once fired would be longer than 65mm. What then happens is that the crimp might not be able to open all the way, which leaves a smaller than usual hole for the shot & wad to be forced through.

    Compounding the situation, older ammo used wads made mostly of felt (or a variety of other "soft" materials) which were easy to compress through the constriction ahead of the chamber. Paper cases also had walls that were thicker than modern plastic cased ammo. Modern ammo therefore has larger diameter wads made of less compressible hard plastic material than older ammo.

    Both the above aspects contribute to why firing modern plastic cased ammo through old barrels can be risky as both cause increased recoil and pressure, which in extreme cases with old guns might lead to damage to the gun.

    As mentioned by KK20, shorter cartridges might allow one to load 1 extra in a (modern) pump action with a tubular magazine. If you want to do this, you've got more chance of achieving it by using star crimped cartridges.

    Buckshot (or slugs) that is mostly manufactured with roll crimps also tends to be loaded with a heavier charge (net result: will kick you harder) than smaller shot sizes that are mostly loaded with star crimps. This is not related to the crimp itself though, just to the heavier charge.

    Hope this hasn't confused more than clarified ;-)

    Edit: Whew, I spent ages writing this, then I see that there was a whole page of answers covering the same things that I didn't see before I started writing......

  3. #23
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    Default Re: Shotgun ammo crimp

    Thanks BBCT, it really is a nice summary

  4. #24
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    Default Re: Shotgun ammo crimp

    If I may add, heavier loads that are star crimped tend to open up in tube magazines while roll crimped ones tend to remain intact.
    There is no difference with low brass and high brass but tend to reserve high brass for buck and solids for ease of identifying buy feel.
    (as per my reloading exp)
    live out your imagination , not your history.

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