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This is a discussion on Roll Crimping within the Reloading forums, part of the Firearm Forum category; Here is my next ? for you gentlemen . Roll Crimping - I think I have a good idea about what it takes but just ...


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Old May 2nd, 2017, 08:14 PM   #1
 
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Roll Crimping

Here is my next ? for you gentlemen . Roll Crimping - I think I have a good idea about what it takes but just want to be sure about everything . I know I'm gonna practice a few time's to get it down because practice does make perfect and when going to the bench that's what I'm always looking for . I never really worry about it that much reloading for my bolt action rifle's so any help would be most appreciated .



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Old May 2nd, 2017, 08:36 PM   #2
 
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Revolvers and tubular magazine rifles require solid crimps to hold the bullet from pulling in a revolver and to prevent bullet set back in a tube magazine. Getting the right amount of crimp can be a bit of a learning process.
It is often best to seat and crimp in seperate operations. Once your bullet is seated with the cannelure (crimp groove) flush with the case mouth, back off the seating stem so it won't interfere with the crimping process. Now with the loaded cartridge raised fully into the die, tighten the die until you feel it contact the case mouth. At this point, lower the ram slightly to extract the cartridge from the die and slowly... incrementally.. screw the die in. Start by first turning the die an 1/8 turn and raising the cartridge into the die. This is where you'll need to develop a "feel" for the crimp. Keep incrementally adjusting the die downward until a good solid crimp is applied without going overboard.
Every little turn of the die, remove your cartridge and inspect the crimp. You want the case mouth to evenly turn inward and mate nicely into the cannelure without damaging the bullet or buckling the case. Once you have a crimp you're satisfied with, lock down the lock ring and run the batch.
NOTE: uniform case length is critical to obtaining consistent crimps. If the case length varies much, so to will crimp quality.
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Old May 2nd, 2017, 08:50 PM   #3
 
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Thanks for the information Owly . I thought I would take a couple test runs with some blanks to get the real feel .



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Old May 2nd, 2017, 09:48 PM   #4
 
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I prefer a taper crimp for my handgun cartridges. My 2 cents.
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Old May 3rd, 2017, 07:00 AM   #5
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The OP didn't state what cartridges he will be loading .... and it does make a difference. For handgun cartridges, the industry standard is a roll crimp for revolver cartridges and a taper crimp for semi-auto cartridges. For rifle, the only cases that need to be crimped are for semi-autos and tube fed models. These typically use a roll crimp but can also use a taper crimp, depending on the bullet used. Any time you see a cannelure on a bullet (rifle or handgun) it means that bullet was intended for a roll crimp. Any time you see a smooth (no cannelure) bullet, it means use a taper crimp. For bolt action rifles, no crimp is needed. So .... let the bullets be your guide.

70Dart340, The only time a taper crimp is used with handguns is when you use bullets intended for semi-autos. One of the very few revolver examples is a 45 Colt loaded with 45 ACP bullets. It will use a taper crimp. The reason for using a roll crimp is to get a better grip on the bullet. This helps powder to get a more uniform burn plus it helps prevent bullet jump. Roll crimps don't work well with semi autos because the "roll" actually shortens the case a little, which causes excessive headspace. Excessive headspace affects accuracy and positive primer detonation. So .... back to basics ..... roll crimp for revolvers, taper crimp for semi-autos.
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Old May 3rd, 2017, 07:20 AM   #6
 
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Just my 2 cents..the neck tension of the case holding the projectile is the main issue as to the way a bullet is held...I have seen (and I have to admit from the early days) I'd try and really mash down on the crimp to gain grip and pressure...often with lead bullets...when I should have been paying attention to the neck tension that the neck of the case exerts on the bullet...

I got in a pickle way back when I was loading 45 Colt for the first few times....lead projectiles (quite soft ones) and they would fail the "push test" against my bench..so I just ratcheted up the crimp until I was deforming and mashing the bullets and gaining nothing....so make certain neck tension is proper and then do your crimping.
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Old May 3rd, 2017, 08:11 AM   #7
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My way of crimping, from an old machinist/mechanic. For roll crimping I seat the bullets so the mouth/lip of the case is even or a few thousandths below the top edge of the cannalure or crimp groove. I then adjust the die so that the case metal is rolled about half way into the groove, or to the cannalure. (kinda hard to describe) The lip of the case rolled into the cannalure enough that it touches the cannalure/knurled portion, not necessarily digging into the bullet side. On a lead bullet with a crimp groove I like to roll the case lip about half way to the base/ID of the groove. This is a good starting place and one way to determine amount needed is to compare your crimp with factory ammo. As opos noted, neck tension plays a major part in holding the bullet in place, so I like to use just enough crimp to hold my Magnum bullets in place.

I also use a Redding Profile Crimp die for my .44 Magnums and .357 Magnums. It is kinda a "hybrid" roll/taper crimp. I get even crimps and it seems to take a bit less crimp to do the same job as a roll crimp. I have also recently purchased a Lee collet crimp die for .44 Magnum, and it seems to be working quite well.

Last edited by mdi; May 3rd, 2017 at 08:14 AM.
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Old May 3rd, 2017, 08:18 AM   #8
 
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Here's my 2 cents!
1. Always pay attention to what Iowegan says!
2. Opos' comment about neck tension is the key!

For good or bad, my first caliber to reload was the 460 S&W magnum. I simply couldn't afford to pay $2 per round for factory ammo. I ruined several cases trying to learn how to get the crimp right. Turns out, the biggest issue was the neck tension. I learned ( the hard way) that you can destroy the neck tension by crimping too much. That may seem counter intuitive, but when you crimp too hard, not only do you squash the bullet, but in pushing the rim down too hard, it actually pulls away from the bullet and forms a little bulge just below the crimp. By pulling the case away from the bullet, you lose all the neck tension, so the bullet moves on recoil anyway. So, when roll crimping, you only want to crimp as hard as you need to, without squashing the bullet and forming a bulge ring around the case. For something like a 38 Special, it doesn't take much of a crimp. For my 460 S&W Magnum, well, that's a different story!
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Old May 3rd, 2017, 08:47 AM   #9
 
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You stated " roll crimping " so you know the difference between taper and roll.

Cast bullets , for revolvers , usually have a generous crimp groove that you can turn ( roll)the mouth into and thus get a heavy crimp without bulging the case.

Jacketed bullets have a cannelure , a ring of ridges to crimp more onto than into. You have to use a much lighter crimp here , just enough to turn the case edge into the ridges, too much will get a bulge . The cannelure is a bit trickier than the cast bullet's crimp groove. So start light.

If a bullet has neither , use a taper crimp.

Those who can't seem to master the art of crimping buy a Lee Factory Crimp Die and use that....takes some of the proper adjustment that's required with regular dies out of the picture . I learned how to use regular dies so do not use the Lee FCD.
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Old May 3rd, 2017, 08:50 AM   #10
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BW45, Well said! To add a bit to the neck tension issue .... neck tension should provide about 90% of the total tension on the bullet. That means the crimp only adds about 10%. Whenever you try to crimp too much, it is counterproductive, just as BW45 said.

I've posted this before but I think it is worth posting again .... my home brew neck tension tester. It is a Lee 45 Colt bullet seater die with a Ruger Blackhawk hammer spring installed inside the threaded cap. It can be adjusted for any cartridge from a 9mm to a 45 Colt by merely threading the die into the press until the last couple inches of your handle throw pushes the bullet against the spring loaded seater stem. This applies about 25 lbs of pressure on the bullet so if neck tension and crimp are too light, the COL will reduce because the bullet will seat deeper. I use this tool a lot when I'm setting the crimp die. To support BW45's post, if I try to crimp too hard, the bullet will push in when using this tool. With no crimp at all, the bullet usually doesn't push in unless the cases are tuckered out.

I've found if my cartridges pass the bullet neck tension test, they will cycle and shoot well with no bullet jump or in the case of semi-autos, the bullets don't push in while feeding.


Last edited by Iowegan; May 3rd, 2017 at 08:57 AM.
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Old May 3rd, 2017, 05:25 PM   #11
 
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In the For What it's Worth [FWIW] category; I've always preferred to seat and crimp in separate operations. I know how to set up a combination seating/crimping die and have done it but, IMO, it is far easier to do those processes in separate steps. Furthermore, it's way easier to fine tune those steps when they aren't interrelated.

Set the seating die to achieve the desired result and lock it down - done. Move on to the crimp die and play with that until you get what you want. When you're happy with the crimp (taper or roll type), lock the die down - DONE !

Using a separate seating & crimping die may add another step to the reloading process when you're using a single stage press but unless you're loading huge numbers of cartridges on a single stage press, it's a non-issue. If you are loading huge amounts of cartridges - get a progressive press ! The seating and crimping processes are separate on most progressive presses so it's a non-issue again.

just my $0.02 worth.
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Old May 3rd, 2017, 07:18 PM   #12
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Petrol and Powder, I do the same thing ..... separate the bullet seating function from the crimp function. I load most of my handgun ammo on my Dillon RL550 so it's easy with a 4 stage progressive. Dillon dies have a dedicated bullet seater die that doesn't crimp and a dedicated crimp die that doesn't seat bullets. When I use my single stage Rockchucker with RCBS combination seater/crimp dies, I still follow the same concept. I seat all bullets then readjust the die and crimp all cases. That said, all those handle pulls on a single stage sure makes you appreciate a progressive press where each pull of the handle produces a finished round.
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Old May 3rd, 2017, 09:39 PM   #13
 
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Do the Lee 4 dies sets use a roll crimp die for revolver cartridges as part of their "factory crimp" sets? I've just learned something else. Just proves you can teach an old dog new tricks......
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Old May 3rd, 2017, 09:59 PM   #14
 
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After examining some of my .357 handloads, they are in fact roll crimped. Thank You, Iowegan, for enlightening me.
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Old May 4th, 2017, 04:21 AM   #15
 
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The vast majority of my handgun cartridges are loaded on a Dillon 550B, so there's a separate station for the crimp die. When I do use a single stage press for handgun rounds I still separate the seating & crimping operations for the reasons previously stated.
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