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Discussion Starter · #1 ·
Hello all, I am relatively new to handloading and have a few questions about crimping. I am reloading .45 colt rounds for a new Ruger Blackhawk, using RCBS carbide dies and the seating die is able to do a rolled crimp. In looking through the reloading manuals for various loads I have noticed that some loads say a crimp is necessary, while others do not mention a crimp at all. I just have a few questions about crimping:
1. Do all loads need to be crimped, or just the ones that the manuals specifically say need to be crimped?
2. What are the benefits of crimping?
3. Are there ever any times when crimping should not be performed?
4. Should I crimp with the seating die or go ahead and get a die specifically for crimping?
5. Difference between a rolled crimp and tapered crimp?
6. As a beginner, one of the tough things is figuring out what I need to know so if there is somethings you all think are beneficial for me to know that I haven't asked please tell me.
Thank you everyone in advance, this is a great forum!
 

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Most reloaders do not crimp rifle ammo unless it will be used in a tubular magazine or perhaps in a semiauto rifle. The crimp keeps the bullet from being shoved deeper into the case due to spring pressure in the tube magazine or the violent shove it gets into the feed ramp on an auto.

Crimping is generally necessary for revolver rounds for two reasons, first, to keep the bullets from coming out of the case during recoil of another round being fired and possibly jamming the cylinder, and second, for more consistent ignition of the powder charge and better accuracy. A proper crimp on ammo for a semiauto pistol keeps the bullet from being driven into the case during feeding and also makes feeding smoother in general.

A medium crimp is appropriate for most loads. A firmer crimp is needed for heavier loads. Most revolver ammo is loaded using a roll crimp, and most ammo for semiautos is done using a taper crimp. The roll crimp folds the end of the case into the crimp groove on the bullet, and the taper crimp squeezes the case walls down so that they grip the bullet more tioghtly, without folding the end of the case. You can use a taper crimp on bullets that don't have a crimp groove.

You can do an good job with the crimp feature of your seating die, but many of us nut jobs who are really serious about this stuff prefer to get a separate crimp die, such as the Lee Factory Crimp Die. It works well and allows you the satisfaction of having more stuff on your loading bench.
 

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I can give you all sorts of reason why you should crimp and not to crimp, I crimp almost all of my ammo. Many of my reloads I use the Lee Factory Crimp Die, I have a Pacific taper die for 45 ACP and 9mm.

Now roll crimp versus taper crimp is a whole different subject.

Jerry
 

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Answer to original question #3. Usually cast bullet loads in bottleneck case rifle cartridges are not crimped.

If crimping is to be done, jacketed bullet loads in rifle cartridges are usually done best with a taper crimp if ample bullet pull (case neck tension on bullet) is present. This goes for bullets with or without cannelure.

I don't want to get into an argument against Richard Lee's theory behind the benefits of the "factory crimp." For handloaders, there are times when the factory crimp die comes in handy but I don't use it routinely. The major manufacturers (RP, WW) who use factory crimp on finished ammunition do it for two reasons, (1) It allows them wider tolerance on case length, and (2) It's insurance against a loose bullet. They don't do it to enhance accuracy, as most people who shoot factory ammo can't tell the difference -- deer rifle accuracy is good enough for most buyers.
 

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Discussion Starter · #5 ·
Answer to original question #3. Usually cast bullet loads in bottleneck case rifle cartridges are not crimped.

If crimping is to be done, jacketed bullet loads in rifle cartridges are usually done best with a taper crimp if ample bullet pull (case neck tension on bullet) is present. This goes for bullets with or without cannelure.

I don't want to get into an argument against Richard Lee's theory behind the benefits of the "factory crimp." For handloaders, there are times when the factory crimp die comes in handy but I don't use it routinely. The major manufacturers (RP, WW) who use factory crimp on finished ammunition do it for two reasons, (1) It allows them wider tolerance on case length, and (2) It's insurance against a loose bullet. They don't do it to enhance accuracy, as most people who shoot factory ammo can't tell the difference -- deer rifle accuracy is good enough for most buyers.
What exactly is the "factory crimp"? Is this the same thing as a normal crimp that I can do with my RCBS seating die or does the Lee crimping die do something different?
 

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It's quite different. Look at any round of factory ammo and you'll see what look like short segments of the neck pushed straight in from the side, not rolled in around the whole circumference. The factory crimp looks like a series of dashes.

Roll and to some extent taper crimps work by pushing the loaded round into a crimping shoulder or angle. Because it is pushed in, an excessive crimp can crumple the case walls. A factory crimp (like Lee uses) exerts all its force perpendicular to the case mouth, so it not only can extert more force, but can NOT crumple the case walls. Jaws squeeze the case, and can even crimp to a bullet with no relief cannelure. Without damaging accuracy, I'll add.

To answer your general questions, higher bullet pull is good, whether created by neck tension or crimp. A "locked" bullet can not be pushed deeper (by a semi-auto or lever) or pulled out (by a revolver). It also significantly improves powder ignition and consistent pressure rise. Rifles and revolvers generally use a roll crimp, whereas semi-autos - which headspace on the case mouth - use a taper crimp. Cast bullets have a deeper relief cannelure/groove and can be crimped harder than jacketed bullets.

In summary, always crimp revolver and lever-action rounds. Usually crimp semi-auto rounds. With bolt and single-shot rifles, crimp is not mandatory, but it seldom hurts anything.
 

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Additionally, crimp will help on rifle rounds were the throats are deeper. An example would be my Ruger 77 in 6.5x55. The throat is deep to accept the longer 160 gr RN bullet that was originally fired in the M96 Swede, but which not very many people use anymore. Seating bullets of 120 and 140 grains anywhere near the normal distance to the lands is not possible, so I crimp them in order to get a uniform starting pressure and enhanced accuracy. I've proven it to myself, as this was the only way to get this rifle to fire with accuracy using my handloads...
 
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