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Old 03-25-2010, 06:33 AM
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Default Taper vs. roll crimp for revolver rounds

OK, Could someone please explain why some revolver rounds have a roll crimp and some have a taper crimp. Thanks.
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Old 03-25-2010, 06:47 AM
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Taper crimp is typically used only for semi-auto cartridges that headspace on the case mouth. All rimmed cartridges headspace on the rim and are typically roll crlmped. You will find that some heavy revolver loads specify a "heavy" crimp for proper ignition.
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Old 03-25-2010, 07:27 AM
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So all revolver cartridges are roll crimped?
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Old 03-25-2010, 08:24 AM
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the pistol chamberings originally designed for semi-auto's are taper crimps but held by the extractor groove in 'moon' or half or 1/3rd moon clips for use in revolvers.
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Old 03-25-2010, 08:26 AM
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I don't recall ever seeing any factory revolver ammo that wasn't roll crimped.

You will find many internet forum members who say they taper crimp theirs, but they are usually talking about light target loads. Rolled crimps serve to keep the bullets from being pulled out of the cases from recoil and to help slower burning powders burn more efficiently and uniformly. They also help keep the bullet from being seated deeper in case the cartridge is dropped.

For the most uniformity using roll crimping, the brass should all be the same length. Those that taper crimp do so to keep from having to trim their brass, which most people don't do anyway for handguns.
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Old 03-25-2010, 12:50 PM
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I have only reloaded 45acp on a Dillon Square Deal B up to now. I recently bought a single stage press to start reloading 44 spl. So, do I have to roll crimp 44spl or can I taper crimp since I am not going to load anything too heavy? And is that a special die, or is that the "fourth" die in the Lee set?
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Old 03-25-2010, 01:12 PM
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It is very likely that your .44SPL dies are roll crimp dies. I suppose someone may sell taper crimp dies for the 44, but I wouldn’t know who it might be.
Factory Crimp dies for the 44 will be roll crimp.
As you can see above the only real question comes in the case of rimless auto loading cartridges shot in revolvers. Since they do not have to locate on front edge of the case, you have an option in crimping. Although you can have a really good argument about whether in practice semi-autos really space on that edge or are held in place by the extractor.

All that said, IMO you are better off crimping, whether roll or taper in a separate step after bullet seating. Thus the fourth stage.
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Old 03-25-2010, 01:57 PM
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Default Another exception is .45 autorim

Since they are typicly reloaded using .45 ACP dies, they would be taper crimped. I have never had any problems with bullet movement in autorim cases.
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Old 03-25-2010, 02:05 PM
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But there is those copper plated bullets from Berry's who is without a cannelure/groove. -- I have used a light taper crimp on those.

There is also a crimp die from Redding who is making a crimp called profile crimp. That is a taper+roll crimp.

PS! I always shoot light start loads.


regards khpe
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Old 03-25-2010, 04:57 PM
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A taper crimp is used forall semi auto cartridges. I also use a taper crimp for plated bullets in revolver cartridges so as not to break the plating. I use a roll crimp for revolver cartridges with lead bullets and jacketed bullets with a cannelure.
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Old 03-25-2010, 05:06 PM
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I flush seat wadcutters in .38 Special and use a taper crimp for that.

Semi-wadcutters get the roll crimp. As has been mentioned, case length should be uniform for the best results with a roll crimp; not so much with the taper crimp.
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Old 03-25-2010, 05:54 PM
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Looking at the factory .38's I have on hand, the jacketed bullets are taper crimped and the lead bullets are roll crimped.
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Old 03-25-2010, 06:18 PM
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Default Crimp testing ammo.

One suggested way to confirm that your reloads are properly crimped is: Fully load your revolver. Fire all but one chamber. Remove the empty hulls and the unfired round. If the unfired round shows ANY movement of the bullet, usually out of the case, your crimp is not tight enough.
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