Rolled crimp? Taper crimp? Factory crimp? Whats the difference?

spleify · August 11, 2009, 08:08 PM

In conjunction with my other thread asking about crimping, what is the difference between a rolloed crimp, a taper crimp, and the one that i have a question about most is factory crimp.

So it is my understanding that the Lee 3 die set I have for my .44 mag will also give me a roll crimp when using the bullet seating die. Is this true? And is this a sufficient crimp, or do I need a seperate die? I also have a 4 die set for my .45 ACP, the forth die is a " carbide factory crimp die". Does this step need to be taken while loading, or is the bullet seating die sufficent for crimping.

Thanks as always for the help

Doodlebugger45 · August 11, 2009, 10:31 PM

The difference between a roll crimp and a taper crimp is a matter of degree. And yeah any 3 die set can do both of them. The crimp is normally applied by your seating die. Screw the die in until it only touches the case mouth and you will get no crimp. Screw it in a little bit more and you will get a taper crimp. A taper crimp is hard to see with your eye, it is more like applying neck tension to the case mouth. But screw it in a bit more and IF you have a crimping groove, the case mouth will start to buckle inward a little bit. Simple compression of the brass between the die and the case head. Supposedly, if you apply too much compression, the case will start to buckle somewhere else besides the mouth.

It all works well, but the first uncertainty is how much crimp do you want? Well play around and get a modest roll crimp on your .44 until it just "looks" about right. It's kind of a gut feel. You don't need a whole lot normally.

The second difficulty comes because you are using one die to do 2 things. You want to seat the bullet to the proper depth but while that bullet is moving into position, you are trying to crimp the brass at the same time. Getting things adjusted just right is kind of tricky. You get the seating plug set so that the bullets are seating right but then you want more crimp, so you have to screw the die body in a little bit more. Guess what? that changes the depth of the seating plug too right? So you have to screw that out a little bit.

After while, you get a feel for it but at first you are changing 2 different variables, the seating depth and the crimping amount at the same time. It gets annoying at first.

So, there are 2 ways of doing it so it's not as complicated. First way is the cheapest. Set your die body so that the outside (controlled by the die body setting) is not contacting the case mouth at all. Back it out so that it's not applying any crimp at all. Then lower just the seating plug all by itself until you get the right seating depth. Then seat all your bullets to the proper depth. Now, screw the seating plug WAY out so that it's not jacking around with the bullets that you set perfectly already. Shoot, take the whole plug out if you want. But just play around with the die body. Screw it further into the press until it starts to deform the case mouth a little bit. Crimp one and see if it's enough. Screw it in a tiny bit more (an eighth of a turn maybe) and see what that crimp is like. Keep doing it until you get the desired crimp.

The other way is to buy a Factory Crimp Die. It basically does the last step I described using a different method. It will do anything from a light taper crimp up to a full neck roll crimp. It will even make a crimp on bullets that don't have a crimping groove if you want, although that's a bad thing usually. But it uses sideways pressure to make the crimp, not vertical compression with the hope that the case mouth buckles and forms a crimp.

Factory Crimp Dies kind of take away a bit of uncertainty. When I first started and found them, I thought they were wonderful. Now that I have a better feel for things, they aren't as necessary at all. I can crimp in the same motion as seating if I fool around with the settings for a few minutes. Or I can crimp with the seating die as a separate step if I want to. But for the calibers that I own a FCD, well I use it and love it.

spleify · August 11, 2009, 10:52 PM

Doodlbug you are great!! Wow does that help out a ton!

Thanks so very much for all your help on this>

What a great site, I am so glad I found you guys.

Spleify

Shoney · August 11, 2009, 11:18 PM

Crimp - The compressing or turning in of the case mouth, usually into a cannelure (crimping groove) in the bullet's circumference, to provide a firmer grip on the bullet. The object is to prevent the bullet extruding from the case neck during recoil, or from being shoved deeper into the case by contact with the front wall of the magazine during recoil. With shotshells the term usually applies to the closure at the case mouth. Also the crimping of the primer pocket around the primer to seal it.

CRIMP, PRIMER - A forcing inward of the brass around the top of the primer pocket. This is frequently found on military cartridges and is done to prevent set-back of primers. The crimp must be removed before repriming the case.

CRIMP, ROLLED – For Revolver cartridges it is the constriction of the mouth of the cartridge into a cannelure on jacketed bullets or a crimping grove on lead bullets, and is to prevent the bullet extruding from the case neck during recoil. It keeps the bullet from moving The closure of the mouth of a shotshell by inverting the mouth of the tube over a top wad or slug.

CRIMP, STAR - A type of closure of the mouth of a metallic case or shotshell in which the sidewalls are folded in a star-shaped pattern. Also called Rose Crimp or Pie Crimp.

CRIMP, TAPER = is used on straight wall semi-auto pistol that headspace off the mouth of the case, and on some straight wall rifle cartridges. It is narrowing of the case along the sidewall of the bullet at the mouth of the case The pressure from the narrowed case keeps the bullet from being shoved deeper into the case by contact with the front wall of the magazine during recoil.

spleify · August 11, 2009, 11:51 PM

Awesome information!! Thanks shoney!

FlyFish · August 12, 2009, 09:34 AM

Roll crimps and taper crimps are two entirely different things and are done by different dies - you can't apply a proper taper crimp with a roll crimp die (you can turn the edge back to remove the bell, but that's not a true taper crimp), and you can't apply a roll crimp with a taper crimp die. If you look at the product catalogs of the major reloading die manufacturers, you'll see that their dies are identified specifically as either roll crimp or taper crimp, with the two different dies offered for some cartridges.

Taper crimping is used on cartridges that headspace on the case mouth (e.g., .45 ACP, 9mm, .380 ACP), typically fired from semi-auto handguns. It compresses the brass to allow a better grip on the bullet while preserving the sharp edge of the brass that's necessary for headspacing. Bullets for taper crimping typically don't have (or need) a cannelure. A properly applied taper crimp will not be obvious on a quick visual inspection. FWIW, there's a school of thought out there that taper crimps are useless because the brass springs back and doesn't maintain pressure on the bullet, but that hasn't been my experience.

Roll crimping, as the name implies, rolls the edge of the case mouth into a cannelure (groove) on the bullet, which effectively means the case mouth can no longer be used to achieve proper headspace. That's fine, because handgun cartridges, usually those for revolvers, (e.g., .38 Special, .44 Mag, .45 Colt) and rifle cartridges (e.g., .30-30) that are typically roll-crimped headspace on the rim.

And just to wrap up - most modern rifle cartridges of bottleneck design headspace on the shoulder of the case and are not crimped at all.

The Lee Factory Crimp Dies - at least those intended for straight-walled pistol cases, which is all I've ever used - also include a carbide sizing ring that performs a final overall sizing of the cartridge, intended to ensure proper function. Some reloaders consider that to be a crutch, but I don't see the problem with it.

bigted1956 · August 14, 2009, 11:51 AM

these have been very good descriptions of crimping and id just add this for kicks.

the adjustment is really simple to achieve when done the way i do and have done for years.

adjust your body down till it just touches the case mouth and back it up two full turns so it no way contacts the case mouth.
now adjust the boolit seater down to seat the boolit to the desired depth,,,also make sure that the chanelure is rite there where you will want to crimp.
now run the depth adjuster way up so it does not touch the boolit and readjust the body till you get the desired crimp and the case is " rolled " into the chanelure of the boolit.
next with the body locked into place where it gives you the desired crimp,,,spin our boolit seater down to meet the boolit. this is a feel thing that was mentioned but is pretty simple to aquire the feel for. when the boolit seater is in place against the boolit and your body is locked in place for the proper crimp,,,lock the boolit seater in place and withdraw the loaded cartridge.
next put a primed, sized, powder charged cart into the shell holder and place another boolit on top making sure the boolit is straight with the case and pull down on the handle,,,,,,,if everything is correct,,,,,walla there is a seated and crimped cartridge.
repeat till done with your run.

i do this every time i start to seat boolits on any cartridge,,,every time...just so i am certain that every time is done the same way and i always get nice, crimped and good looking and functioning shells.

amamnn · August 14, 2009, 02:17 PM

We should mention that there is a difference between the Lee rifle factory crimp die and the pistol versions. The Rifle die crimps by squeezing a collet on the case mouth. The pistol dies operate in the same manner as other roll or taper crimps with the exception of the Redding profile (roll) crimper for revolver cases.

August 11, 2009, 08:08 PM	#1
spleify Senior Member Join Date: August 3, 2009 Location: Denver, Colorado Posts: 151	Rolled crimp? Taper crimp? Factory crimp? Whats the difference? In conjunction with my other thread asking about crimping, what is the difference between a rolloed crimp, a taper crimp, and the one that i have a question about most is factory crimp. So it is my understanding that the Lee 3 die set I have for my .44 mag will also give me a roll crimp when using the bullet seating die. Is this true? And is this a sufficient crimp, or do I need a seperate die? I also have a 4 die set for my .45 ACP, the forth die is a " carbide factory crimp die". Does this step need to be taken while loading, or is the bullet seating die sufficent for crimping. Thanks as always for the help

August 14, 2009, 11:51 AM	#7
bigted1956 Junior Member Join Date: August 5, 2009 Posts: 14	die adjustments these have been very good descriptions of crimping and id just add this for kicks. the adjustment is really simple to achieve when done the way i do and have done for years. adjust your body down till it just touches the case mouth and back it up two full turns so it no way contacts the case mouth. now adjust the boolit seater down to seat the boolit to the desired depth,,,also make sure that the chanelure is rite there where you will want to crimp. now run the depth adjuster way up so it does not touch the boolit and readjust the body till you get the desired crimp and the case is " rolled " into the chanelure of the boolit. next with the body locked into place where it gives you the desired crimp,,,spin our boolit seater down to meet the boolit. this is a feel thing that was mentioned but is pretty simple to aquire the feel for. when the boolit seater is in place against the boolit and your body is locked in place for the proper crimp,,,lock the boolit seater in place and withdraw the loaded cartridge. next put a primed, sized, powder charged cart into the shell holder and place another boolit on top making sure the boolit is straight with the case and pull down on the handle,,,,,,,if everything is correct,,,,,walla there is a seated and crimped cartridge. repeat till done with your run. i do this every time i start to seat boolits on any cartridge,,,every time...just so i am certain that every time is done the same way and i always get nice, crimped and good looking and functioning shells.

August 11, 2009, 10:31 PM	#2
Doodlebugger45 Senior Member Join Date: April 15, 2009 Location: Wyoming Posts: 1,717	The difference between a roll crimp and a taper crimp is a matter of degree. And yeah any 3 die set can do both of them. The crimp is normally applied by your seating die. Screw the die in until it only touches the case mouth and you will get no crimp. Screw it in a little bit more and you will get a taper crimp. A taper crimp is hard to see with your eye, it is more like applying neck tension to the case mouth. But screw it in a bit more and IF you have a crimping groove, the case mouth will start to buckle inward a little bit. Simple compression of the brass between the die and the case head. Supposedly, if you apply too much compression, the case will start to buckle somewhere else besides the mouth. It all works well, but the first uncertainty is how much crimp do you want? Well play around and get a modest roll crimp on your .44 until it just "looks" about right. It's kind of a gut feel. You don't need a whole lot normally. The second difficulty comes because you are using one die to do 2 things. You want to seat the bullet to the proper depth but while that bullet is moving into position, you are trying to crimp the brass at the same time. Getting things adjusted just right is kind of tricky. You get the seating plug set so that the bullets are seating right but then you want more crimp, so you have to screw the die body in a little bit more. Guess what? that changes the depth of the seating plug too right? So you have to screw that out a little bit. After while, you get a feel for it but at first you are changing 2 different variables, the seating depth and the crimping amount at the same time. It gets annoying at first. So, there are 2 ways of doing it so it's not as complicated. First way is the cheapest. Set your die body so that the outside (controlled by the die body setting) is not contacting the case mouth at all. Back it out so that it's not applying any crimp at all. Then lower just the seating plug all by itself until you get the right seating depth. Then seat all your bullets to the proper depth. Now, screw the seating plug WAY out so that it's not jacking around with the bullets that you set perfectly already. Shoot, take the whole plug out if you want. But just play around with the die body. Screw it further into the press until it starts to deform the case mouth a little bit. Crimp one and see if it's enough. Screw it in a tiny bit more (an eighth of a turn maybe) and see what that crimp is like. Keep doing it until you get the desired crimp. The other way is to buy a Factory Crimp Die. It basically does the last step I described using a different method. It will do anything from a light taper crimp up to a full neck roll crimp. It will even make a crimp on bullets that don't have a crimping groove if you want, although that's a bad thing usually. But it uses sideways pressure to make the crimp, not vertical compression with the hope that the case mouth buckles and forms a crimp. Factory Crimp Dies kind of take away a bit of uncertainty. When I first started and found them, I thought they were wonderful. Now that I have a better feel for things, they aren't as necessary at all. I can crimp in the same motion as seating if I fool around with the settings for a few minutes. Or I can crimp with the seating die as a separate step if I want to. But for the calibers that I own a FCD, well I use it and love it.

August 11, 2009, 10:52 PM	#3
spleify Senior Member Join Date: August 3, 2009 Location: Denver, Colorado Posts: 151	Doodlbug you are great!! Wow does that help out a ton! Thanks so very much for all your help on this> What a great site, I am so glad I found you guys. Spleify

August 11, 2009, 11:18 PM	#4
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Crimp - The compressing or turning in of the case mouth, usually into a cannelure (crimping groove) in the bullet's circumference, to provide a firmer grip on the bullet. The object is to prevent the bullet extruding from the case neck during recoil, or from being shoved deeper into the case by contact with the front wall of the magazine during recoil. With shotshells the term usually applies to the closure at the case mouth. Also the crimping of the primer pocket around the primer to seal it. CRIMP, PRIMER - A forcing inward of the brass around the top of the primer pocket. This is frequently found on military cartridges and is done to prevent set-back of primers. The crimp must be removed before repriming the case. CRIMP, ROLLED – For Revolver cartridges it is the constriction of the mouth of the cartridge into a cannelure on jacketed bullets or a crimping grove on lead bullets, and is to prevent the bullet extruding from the case neck during recoil. It keeps the bullet from moving The closure of the mouth of a shotshell by inverting the mouth of the tube over a top wad or slug. CRIMP, STAR - A type of closure of the mouth of a metallic case or shotshell in which the sidewalls are folded in a star-shaped pattern. Also called Rose Crimp or Pie Crimp. CRIMP, TAPER = is used on straight wall semi-auto pistol that headspace off the mouth of the case, and on some straight wall rifle cartridges. It is narrowing of the case along the sidewall of the bullet at the mouth of the case The pressure from the narrowed case keeps the bullet from being shoved deeper into the case by contact with the front wall of the magazine during recoil.

August 11, 2009, 11:51 PM	#5
spleify Senior Member Join Date: August 3, 2009 Location: Denver, Colorado Posts: 151	Awesome information!! Thanks shoney!

August 12, 2009, 09:34 AM	#6
FlyFish Senior Member Join Date: January 20, 2009 Location: Overlooking the Baker River Valley Posts: 1,731	Roll crimps and taper crimps are two entirely different things and are done by different dies - you can't apply a proper taper crimp with a roll crimp die (you can turn the edge back to remove the bell, but that's not a true taper crimp), and you can't apply a roll crimp with a taper crimp die. If you look at the product catalogs of the major reloading die manufacturers, you'll see that their dies are identified specifically as either roll crimp or taper crimp, with the two different dies offered for some cartridges. Taper crimping is used on cartridges that headspace on the case mouth (e.g., .45 ACP, 9mm, .380 ACP), typically fired from semi-auto handguns. It compresses the brass to allow a better grip on the bullet while preserving the sharp edge of the brass that's necessary for headspacing. Bullets for taper crimping typically don't have (or need) a cannelure. A properly applied taper crimp will not be obvious on a quick visual inspection. FWIW, there's a school of thought out there that taper crimps are useless because the brass springs back and doesn't maintain pressure on the bullet, but that hasn't been my experience. Roll crimping, as the name implies, rolls the edge of the case mouth into a cannelure (groove) on the bullet, which effectively means the case mouth can no longer be used to achieve proper headspace. That's fine, because handgun cartridges, usually those for revolvers, (e.g., .38 Special, .44 Mag, .45 Colt) and rifle cartridges (e.g., .30-30) that are typically roll-crimped headspace on the rim. And just to wrap up - most modern rifle cartridges of bottleneck design headspace on the shoulder of the case and are not crimped at all. The Lee Factory Crimp Dies - at least those intended for straight-walled pistol cases, which is all I've ever used - also include a carbide sizing ring that performs a final overall sizing of the cartridge, intended to ensure proper function. Some reloaders consider that to be a crutch, but I don't see the problem with it.

August 14, 2009, 02:17 PM	#8
amamnn Senior Member Join Date: May 13, 2006 Location: WA, the left armpit of the USA Posts: 1,323	We should mention that there is a difference between the Lee rifle factory crimp die and the pistol versions. The Rifle die crimps by squeezing a collet on the case mouth. The pistol dies operate in the same manner as other roll or taper crimps with the exception of the Redding profile (roll) crimper for revolver cases.