Understanding Crimping with Seating Die

[sirgilligan]

I am editing this post because there may be a copyright issue with the images...

Sorry

p.s.

Okay, I took the picture and studied it and made my own drawing of it. It shows a seating die set for no crimp and a seating die set for crimp.



What I noticed in the photograph of an actual seating die that had been cut-away was the little notch/taper that forces the rim of the case mouth to turn in to make the crimp. It is very small and therefore turning in the die just a little too much will cause the seating die's taper notch to push the case neck down and when that happens something has to give way, and for me it was the case shoulder.

A picture is worth a 1000 words for sure. I finally understand why it is so unforgiving to setup the crimp wrong.

 

[gamestalker]

So anyway, your having an issue, or maybe just some questions about how to set up your seating die to crimp? Elaborate a bit and maybe we can provide some answers for ya.

GS

 

[Lost Sheep]

The "fair use" clause of the Copyright law allows individuals to quote from other authors' works (particularly if attribution to the original author is included) as long as the quote is not in a for-profit venue.

But you are right to be cautious, for there are ways to overstep.

How about describing your question and providing a link to the web site that has the picture?

Lost Sheep

 

[joem1945]

If your somewhat new to reloading setting the seater/crimp die can be a challenge. Set the die too far down and the shoulder gets a bulge. The way I have done this is to have the die just barley touching the case and the seating plug set the bullet at the right place. Back off the seater plug 2 turns, then raise the ram and adjust the die down 1/8th. turn at a time. Remove the case and inspect the crimp. If it's not enough 1/8 turn more and so on. When it's correct, raise the ram and turn the seater plug down until it contacts the bullet.

 

[HexHead]

Judging from the illustration you posted, why do you feel the need to crimp a rifle round in the first place?

 

[sirgilligan]

Judging from the illustration you posted, why do you feel the need to crimp a rifle round in the first place?

I am the curious type, I wanted to know how the die formed the crimp. Until I had found the photo of the die cut-away I couldn't imagine what it was doing. Not knowing what it was doing meant that I didn't understand what the adjustments were actually adjusting.

 

[gamestalker]

The basic crimp feature of most seating dies is very basic, it simply forces the case mouth to fold inward. This is accomplished by an angled shelf inside the die, that when the brass is run up into the die, the mouth makes contact with that angled portion of the die, then it is forced inward.

Taper crimp is less aggressively folded inward, where as the roll crimp is more aggressively folded inward.

GS

 

[FROGO207]

Your second picture shows the die contacting the case shoulder. This is not the case unless the neck of the brass is trimmed excessively short. I can take standard dies for the 30-30 that were made 30 or so years ago and crimp for the new FlexTip bullets that is trimmed many thousands shorter and it still works. That is why we all say to trim the rifle brass to all be the same length (minimum SAMMI) so that the crimp will be repeatable without buckling the shoulder. Also if you trim the brass and do not chamfer the inside of the neck the bullet itself, especially a flat base will sometimes push the neck down instead of sliding inside. Personally I tried both crimped and no crimp ammo in all the rifle ammo I load. The crimp did not help me that I could measure so now I only crimp for tube fed firearms (my WIN 94 etc.) to prevent bullet setback. If you buy the LEE Factory Crimp die (it uses a set of fingers that push in sideways to crimp) the trim length is not as critical but you have to crimp the neck in a separate step. I do however crimp all my revolver ammo to keep the bullets from moving out unless they are mouse fart loads for my 38 SPL's.

 

[Walkalong]

Your second picture shows the die contacting the case shoulder. This is not the case unless the neck of the brass is trimmed excessively short.

Yep, it shouldn't be touching, but nice pics.

 

[sirgilligan]

The basic crimp feature of most seating dies is very basic, it simply forces the case mouth to fold inward. This is accomplished by an angled shelf inside the die, that when the brass is run up into the die, the mouth makes contact with that angled portion of the die, then it is forced inward.

Taper crimp is less aggressively folded inward, where as the roll crimp is more aggressively folded inward.

GS

I was curious the difference between taper and roll. Thank you. Would a little lube on the rim help, especially for the roll crimp? Also, it seems that chamfering might help it taper or roll over as well.


I have both taper and roll crimp seating dies for .223, and I have the Lee Factory Crimp die.

Now I know how they work I realize that it takes just a little turn of the die downward to get the job done.

I have standard RCBS dies for a Rock Chucker, how far does the die go downward for 1 full turn. I can then figure out how much for 1/16th, 1/18th, and 1/4th.

 

[higgite]

Standard die body threads are 14 TPI, or 0.071" travel per full turn of the die. Seating, crimping and expander stems have a different pitch, depending on the die.

 

[Walkalong]

I was curious the difference between taper and roll.

http://www.thehighroad.org/showpost.php?p=6385988&postcount=75

Heavy Taper

Medium Roll - The inward rolling of the case mouth is affected by how deep the cannelure is. The deeper it is the more the case mouth "rolls" inward. With a shallow cannelure it ends up looking a lot like a taper crimp, but a lot more angle. A true taper crimp is a very shallow angle.

 

[Walkalong]

Would a little lube on the rim help, especially for the roll crimp? Also, it seems that chamfering might help it taper or roll over as well.

No lube needed. Deburring and chamfering is highly recommended.

 

[fguffey]

The seating die does not have case body support, it does not have shoulder support or neck support.

I made a seating die that has neck support and shoulder contact, it does not have a die body.

F. Guffey

 

[GLOOB]

F Guff: I just bought a Lee taper crimp die for 40SW. I thought it would be just like a seater die but without a seater plug/stem.

Boy was I surprised to find out that Lee pistol taper crimp dies have case support! Some of my brass is too thick to use this die with lead bullets. The opening in the die body is too small, and it swages the bullet, FCD style. I have to figure out a way to open up the body.

I should have just bought the seater die body as a spare part.

 

[sirgilligan]

Okay, I found a public domain picture of a seating die with crimp.



Image from US Patent Office

 

[Walkalong]

That's what they look like alright. Some of the crimp ledges are sloppy though.

 

[rsrocket1]

I have both taper and roll crimp seating dies for .223, and I have the Lee Factory Crimp die.

Now I know how they work I realize that it takes just a little turn of the die downward to get the job done.

The Lee FCD for rifle works differently than your diagram at the top. If you have a single stage press, you can easily see how the die works. There are 4 fingers that close up on the neck as the shell holder is pressed into the bottom of the die. The amount of case insertion dictates how far the fingers get pressed into the neck. This allows anything from no crimp to closing the flare to nearly a "roll crimp" into the cannelure.

There is virtually no reason to crimp too much with rifle rounds for most shooters. The heavy crimp into the cannelure for military rounds is to prevent bullet movement during potentially years worth of military transport and rough chambering with auto loading guns and is not a substitute for proper neck tension.

 

[Lost Sheep]

F Guff: I just bought a Lee taper crimp die for 40SW. I thought it would be just like a seater die but without a seater plug/stem.

Boy was I surprised to find out that Lee pistol taper crimp dies have case support! Some of my brass is too thick to use this die with lead bullets. The opening in the die body is too small, and it swages the bullet, FCD style. I have to figure out a way to open up the body.

I should have just bought the seater die body as a spare part.

Buying a crimp/seat combo die and removing the seating stem/plug is, indeed one solution, as you note in your last sentence.

The other solution is to knock the post-sizing ring out of the die. This is not an uncommon practice. (It is not the die body that is too tight, but a carbide ring at the bottom of the die, which is there to ensure any bulges from too-large bullets or too-thick cartridge case walls do not cause chambering problems - see Lee's FAQ section of their web site.)

Lee will also machine the carbide post-sizing ring to your specifications if you want.

Lost Sheep

 

[GLOOB]

Lost Sheep, there's no post sizing ring. This isn't an FCD. It is just a Lee taper crimp die. This is not a die that comes in any of their pistol sets. It looks almost identical to a seater die body, except this one is cut just a skosh tighter. It might be on the tight end of regular tolerances, in fact. And the crimp part looks to be more gradual and ultimately can be set tighter/smaller than the crimp in the seater die. There are some minor esthetic differences - no threading for a seater stem and no outside bevel/chamfer on the die body opening on bottom. (I'm not sure why the Lee seater die opening has an outside bevel?)

I have an FCD, but I use that for bulge busting, so I'm not going to mess with it. And FCD, alone, costs much more than a regular taper crimp or seater die body.

In hindsight, I think my 380 seater die does this on some brass, too. But I didn't use it much, and haven't used it for years. So this might just be part of their normal tolerances. I think I might shoot them an email. And maybe I'm going overboard by saying this swages the bullet. It definitely requires some force to get the round in, and it scratches the heck out of the case, even removing some brass particles. But if it were tight enough to swage a bullet, I think the case might end up getting stuck.

* Well, problem solved. I think. I got to thinking about it, and I decided to just try lapping the die out using the cartridges, themselves. I think it worked. There's still no plunking a cartridge into the die, but at least they can be inserted and removed by hand, at all. Before, the cartridge would wedge partway in; no way to remove the case without a press, if you were to jam the round all the way. But I'll probably have to do some more testing. I used up all my pmc cartridges, and I might have just lapped the brass more than the die, lol. (Maybe I have a new case turning tool?) As for the original topic, I think seater dies can and do support the neck, to the degree that they are able to, anyway. With brass and bullet tolerances figured in.

 

[Lost Sheep]

Lost Sheep, there's no post sizing ring. This isn't an FCD. It is just a Lee taper crimp die. This is not a die that comes in any of their pistol sets. It looks almost identical to a seater die body, except this one is cut just a skosh tighter.

I did not realize Lee made a Crimp-only die for .40 S&W that was not their FCD.

Interesting.

Lost Sheep

 

[Walkalong]

They make them for various calibers. Good stuff.

http://www.midwayusa.com/find?userSearchQuery=lee+taper+crimp+die