Seating bullets with a cannelure . . . ?

[Prof Young]

So after all these years, it occurs to me that I don't know the correct way, or if there even is a correct way to seat a bullet with a cannelure. Assuming the brass will have a crimp, should the brass completely cover the cannelure, or cover half the cannelure or . . . ?

Talk to me please.

Life is good.
Prof Young

[mehavey]

Seat it to cover about 80% of the cannelure then crimp.

[44 AMP]

when using the standard roll crimp, the brass should NOT cover the cannelure. The leading edge of the case should be "in the groove" not covering it.

I'm talking about the standard roll crimp in seating dies, taper crimp and collet crimp dies are a different subject, ok?

The roll crimp shoulder in the die bends (turns in) the case mouth when the case contacts it. For this to work properly, the brass has to have somewhere to go, which is into the cannelure/crimp groove. If the brass has nowhere to go (like being ahead of the groove) the die squeezes it into the bullet. This can deform the bullet, and can even result in the case buckling.

Soft lead bullets can have crimps squeezed into them without problems, but harder bullets and of course jacketed bullets can have issues ranging from mild to major, depending on how much force is being applied when crimping.

When the case mouth is forced to dig into the bullet and the bullet it hard, it can only go so far, before the pressure bulges the case below the crimp. This results in the reduction of the case neck's grip on the bullet, and if taken too far, can result in the case buckling at an unsupported point, and can bulge enough to prevent chambering.

Particularly with bottle necked rifle rounds. The classic is the .30-30 Win, and other similar rounds. It is the leading edge of the case mouth that contacts the crimp shoulder of the die, and get turned in FIRST, and if there's no where for it to go, the case bulges out below it, where the seater die doesn't tightly support the brass. You can get "wrinkles" (bulges) n the case neck, or even worse the case bulges out at the shoulder, enough to prevent the round from being chambered.

Straight wall pistol rounds can have the same sort of thing happen, though not normally to the same degree.

Seat your bullets so that the leading edge of the case mouth is in the groove. Not ahead of, or behind the groove,

Also, there is the "spring back" issue, if you're not in the groove. If you compress the bullet with the crimp (because its not in the groove), the bullet and the case spring back different amounts. The lead stays more compressed than the brass and this reduces the case grip on the bullet. Not a good thing.

Hope this helps explain things for you.

[Shadow9mm]

I always just put the neck in the middle of the cannelure. Whenever I have trimmed brass and seat the bullet to the recommended col that always seems to be where it winds up.

[Prof Young]

Thanks. And how do I know what kind of crimp my die is making? Rolled or something else. I only use Lee dies so . . . .

Life is good
Prof Young

[mehavey]

Looking at Lee's 38SP/357 die,
(Rimmed) 38 Special or 357 Magnum pistol bullet seating die/If crimp is desired, this die will apply a roll crimp.

Looking at 9mm (rimless):
...taper crimp


30-06 rifle (rimless/bottleneck)
...separate "Factory Crimp" die

See https://exhaustnotes.us/blog/wp-cont...sRollCrimp.jpg
For difference between roll & FCD on bottleneck rifle case
https://exhaustnotes.us/blog/index.p...factory-crimp/

[Unclenick]

The purpose of the cannelure is make a pattern with sharp enough ridges to indent the brass at squeeze pressure too low to distort the bullet. In this way, the brass interlocks with the bullet a little, increasing start pressure over what friction with the case neck can achieve. The rule of thumb I've always used is I want to see about 0.015" of cannelue sticking out beyond the case mouth. This means more of the cannelure is below the mouth than above it, which I want because the squeezed brass is spread over some of the width of the cannelure, so getting the middle of that contact area coincident with the middle of the cannelure means having the top edge of the case mouth a little past center. With most pure roll crimps, this isn't critical, but with taper crimps a bigger portion of the cannelure has some of the case brass sunk into it.

These days I mainly use Redding Profile Crimp Dies for revolver loads. These are a hybrid design, with the crimp starting out as a taper and terminating in a roll profile. This addresses a basic problem with the standard roll crimp shoulder, wherein a really firm roll bends the case mouth over so sharply that the stress at the turn lifts the brass just below it outward, causing loss of "neck tension" on the bullet below the crimp, and some loss of contact if it taken far enough. By starting as a taper, the hybrid crimp die traps the brass below the turn in the roll to prevent it from being lifted out away from the bullet sides. The net effect is a firmer crimp can be achieved for warm loads. This can help a lot with loads for light-for-caliber guns.

[Prof Young]

Great information. Thanks to all.

How does one tell what kind of crimp their die engages. I've read all through the instructions that came with my Lee dies. There is nothing that identifies the kind of crimp it creates. Should I be able to tell what kind of crimp it is by simply looking at the finished product?

Life is good.
Prof Young

[Savvy_Jack]

For me I guess it depends on the cartridge/bullet itself. I, like unclenick, use the Redding Profile Crimp Die for both lead and JSP bullets. Taper crimp for lead and the "U" shaped crimp for the JSP cannelure.

I use different dies for different case resizing, as to get the proper neck retention needed when using the jacketed bullet. The "Wasp-Waist" below the base of the bullet, replaces the need for a case cannelure at the base of the bullet.

[Jim Watson]

Yes.
Factory revolver bullets are roll crimped, compare.

[Aguila Blanca]

Originally Posted by Prof Young

Thanks. And how do I know what kind of crimp my die is making? Rolled or something else. I only use Lee dies so . . . .

Read the information that came with the die. That should tell you.

For example, Lee's web site for the 9mm Luger crimping die states, "This die applies a taper crimp."
https://leeprecision.com/carbide-factory-crimp-die-9mm

Their web page for the .44 Magnum crimping die says, "This die applies a roll crimp."
https://leeprecision.com/carbide-fac...p-die-44sp44ma

[Nick_C_S]

Seat it to cover about 80% of the cannelure then crimp.

I'm about there. At least 2/3's of the way.

[RC20]

The Cannelure is supposedly gives you a nominal length cartridge (COAL) that works in barrel chamber and magazines.

So sneak up on it and see how that looks COAL wise. My guess is its an average as a 30 caliber bullet can be used in a number of different cartridges. 308 to 300WM for example.

Yes if its a type (pistol) I used a separate die to crimp. I don't crimp rifle though some of the nasty calibers aka 300 WM, 7mm Mag probably should be if you hunt and have cases in the magazine.

[jetinteriorguy]

Generally with Lee standard die sets for revolver cartridges it’s a roll crimp, semi auto pistols it’s a taper crimp. But Lee also has the Factory crimp die which also incorporates a carbide ring for additional sizing and for magnum revolvers a Collet Crimp die. For rifles they also offer a standard taper crimp die and a Collet Crimp die.

[Jim Watson]

Bullet cannelures, crimp grooves on cast, can lead to OAL Anxiety. Unless you are loading from the bullet company's manual, the printed OAL will seldom come out on the cannelure.
If I am loading for a revolver or lever action rifle, I seat to and crimp in the cannelure and take what OAL it gives me. If loading for a bolt action rifle, I ignore the cannelure.
I don't crimp for target shooting with an AR but you might want to for ammo kept for the breakdown of civilization.

[Nick_C_S]

If I am loading for a revolver or lever action rifle, I seat to and crimp in the cannelure and take what OAL it gives me.

Exactly ^.

The calipers stay in their case.