Crimping question

[areandare]

I am new to reloading and have a question on crimpnig. On a lswc 158 gr. for a 38 special am I supposed to crimp the on the rim or directly behind it in the groove/cannelure?? I have been told both ways and both are within oal. Does it natter when I purchased the lee set I was told to do it on the rim and had no problems it just seems more like it would be a more consistant length doing in the groove.
Thanks

[Unclenick]

Some cast bullets are formed with a crimp groove, while jacketed bullets often have a cannelure where it is intended that a roll crimp go. In the .357 magnum a roll crimp into the cannelure is used because magnum loads require a hard crimp be present to provide adequate start pressure and to keep bullets in a revolver cylinder from backing out under recoil.

In the .38 special the recoil is less dramatic, and besides, you may well have a taper crimp rather than a roll crimp in your die. The taper won’t get into the cannelure as hard as a roll crimp does. I’d have to look the die set up by part number to tell. In any event, for the simple reason that straight wall case peak pressures go up rather quickly as bullets are seated more deeply, I would use the configuration that seats the bullet furthest out without violating the cartridge overall length requirement. From your description, that would be crimping into the cannelure.

[XD-Guy]

The Lee factory crimp die is a taper crimp die which is what you have and you should be crimping in the crimp groove

[rwilson452]

Lee makes both roll and taper crimp dies

[Ausserordeutlich]

Roll crimps are for cannelures; taper crimps are not.

[XD-Guy]

He said he bought a set from Lee and the Lee 4 die set comes with a factory crimp die which is a taper crimp die. I called Lee about the same thing and they told me if the bullet has a crimp groove, then thats where to put the crimp

[carl418]

I have a Lee Factory Crimp die for 38/357, 41 mag, 44 mag and 45 Colt. All of mine are roll crimp dies.

[Rimrod]

If the bullet has a crimp groove or cannelure the case should be roll crimped into the groove or cannelure. Hornady makes some lead bullets that do not have a crimp groove and they should be roll crimped ahead of the bearing surface, this is also true of some full wadcutters.

The easy way to tell if a cartridge should be roll crimped or taper crimped is if the cartridge headspaces off the case mouth (taper)or has a rim (roll). (The .38 should be roll crimped.)

The Lee Factory Crimp Dies purpose is to squeeze the round back into factory specs. If you crimp and seat at the same time it will deform the case enough that it might have trouble chambering. If you don't have a FCD all you have to do is seat and crimp in two seperate operations.

[cheygriz]

Lee FCD dies are made in roll crimp for revolvers and taper crimp for autos. Where to crimp depends on the bullet, the OAL, and what works best in your particular gun.

Generally speaking, a 158 GR lead .38 bullet is roll crimped in the crimping groove.

[XD-Guy]

cheygriz: Thank you for your post. I stand corrected, I didn't know that. So what your saying is that depending on what caliber you order from Lee, the correct crimp die will be in the 4 die set. Very good to know,as I thought all Lee crimp dies were taper crimp.

[amamnn]

I'm surprised at the amount of bad information on a subject as straightforward as crimping. here's a quote from the Sierra external ballistics site, which members of this forum could stand to read, it seems. Either that or a good reloading manual.

Crimping

Crimping is the final reloading operation applied to either rifle or handgun cartridges. Reloading for most straight-wall cases calls for “belling” or expanding the case mouth to accept the bullet. In its most basic form, crimping is simply a “turning in” of the case mouth to remove the flare left by the belling operation. There are several different styles of crimp, with all having virtually the same goal; increased functional reliability. Depending on the type of cartridge and firearm being used, there are particular crimps that are appropriate, and certain styles that should be avoided. Making a proper decision as to which type of crimp should be used requires some understanding of bullet design, and the nature of the crimp involved. While there are several different styles or types of crimps, most will fall into one of two categories; a roll crimp, or a taper crimp. Throughout the rest of this discussion, bear in mind the fact that not all cartridges will require a crimp of any kind. For those cartridges which can be loaded without resorting to a crimp, we recommend omitting this step altogether.

The roll crimp is the most commonly seen style for revolver cartridges. As the name implies, the roll crimp entails forming a slight radius at the case mouth by pressing it inward against the bullet. Most bullets intended for use in revolver cartridges have a cannelure, or crimping groove impressed into the bearing surface. Two good examples of this are Sierra’s .45 caliber 185 grain JHP, and 240 grain JHC. The 185 grain JHP is designed for use in the .45 ACP cartridge and does not have a cannelure, as it is intended to be taper


These three cartridges show varying degrees of crimp. They are (from left to right) a slight or mild crimp, a good firm crimp, and too much crimp. The center example will be correct for most applications.

crimped. The 240 grain JHC, on the other hand, is designed for the .45 Colt revolver cartridge. It has a properly located cannelure and is intended to be roll crimped. It must be clearly understood that a cannelure is essential to obtain good results with a roll crimp. Remember, bullets that do not have a cannelure but need to be crimped should be given a taper crimp.

Taper crimping is the best choice for any firearm which headspaces on the case mouth. Cartridges intended for use in self-loading pistols, such as the .45 ACP, should never be given any type of crimp other than a taper crimp. Because of the method of headspacing on the case mouth, a slight ledge must be left to provide positive positioning of a chambered round.


An example of an improper type of crimp. These .45 ACP cartridges, intended for use in a semi-automatic pistol, have been given a roll crimp. Ammunition which head-spaces on the case mouth should be taper crimped only; roll crimps are best reserved for the rimmed cases commonly used in revolvers.

On these cases, the use of a roll crimp will result in poor ignition, unreliable functioning, and reduced accuracy. Few bullets designed for autos have cannelures, limiting the amount (and type) of crimp that may be applied. On any bullet, if the crimp being applied is heavy enough to cause any visible deformation, you are over crimping! Over doing the crimping reduces accuracy, so we strongly recommend using only the degree of crimp required for your particular loading application.

Regardless of which type of case a crimp is applied, one of the primary reasons for crimping remains the same; to increase neck tension, thereby ensuring proper powder ignition. In many cartridges, such as the .357 and .44 Magnums, large charges of slow-burning powders like H110 and Winchester 296 require firm initial resistance to the bullet’s movement. This building pressure aids in giving complete combustion, enhancing accuracy and shot to shot uniformity.

Despite the mechanical similarities of the differing styles of crimps, understand that the reasons for crimping varies considerably from one gun type to another. Hard-kicking revolvers, for example, require crimping to prevent the bullets from being pulled out of the case under recoil. In extreme cases this may result in the bullets actually protruding out the front of the cylinder, locking it up and effectively rendering the gun useless. A firm taper crimp on ammunition intended for use in an autoloading firearm is intended to do exactly the opposite; to prevent the bullet from being forced deeper into the case during the feeding cycle. It also serves to ensure reliable feeding by eliminating the sharp edge of the case mouth. Rifles having tubular magazines, such as the Winchester Model 94, also require bullets to be firmly crimped to prevent their being forced back into the case under recoil. Neck tension alone should be enough to prevent this from occurring, without resorting to excessive crimping. We regard this as a poor solution to an easily cured problem. Still, many reloaders do attempt to increase neck tension through the use of a tight taper crimp, with varying degrees of success.

Most manufacturers offer seating dies with built-in crimpers, particularly for those cartridges that predominantly utilize the roll crimp. Despite this, we continue to recommend that seating and crimping be done in separate operations. This can be easily accomplished in a single stage press by raising the seating die body enough that the case is not crimped at all when the press is at the top of the stroke. Adjust the seating stem to seat the bullet at the proper OAL, and seat your bullets without any crimp. When this is done, raise the seating stem to the top of its range, or better yet, remove it completely. With the ram at the top of its stroke, and a loaded cartridge in the shell holder, loosen the lock ring on the die and lower the body down to until you feel it contact the case mouth. Lower the ram, and adjust the die body down approximately 1/4 of a turn. Run the cartridge back through the die, and examine the crimp that has now been applied. If more crimp is called for, lower the ram, and adjust the die body down another 1/8 of a turn. Run the cartridge back through the die, and re-examine the crimp. Continue this process until the crimp is correct. Once the proper adjustment is attained, tighten the lock ring, and crimp the rest of your cartridges.

[Ausserordeutlich]

Taper crimps for semi-auto cartridges are not done for the "primary reason of increasing neck tension." They're only done to remove the bell and have practically nothing to do with preventing setback or providing neck tension.

[Unclenick]

Oh dear! Lots of stuff to disagree with! For one thing, a good bit of history seems to have been forgotten.

Originally Posted by Sierra

. . . On any bullet, if the crimp being applied is heavy enough to cause any visible deformation, you are over crimping! Over doing the crimping reduces accuracy. . .

This was part of the great argument between Sierra and Lee, who, without naming names, ranted at each other rather publicly in their advertising for a couple of years after Lee's Factory Crimp die for rifles was introduced. Sierra doesn't want their bullets indented, and Lee's Factory Crimp die does just that. Lee is correct to suggest this is the way many factories do it. Pull some Lake City M2 ball sometime; no bullet cannelure, but a hefty indentation is present around the middle of the bearing cylinder of the bullet. The LC M2 produces dubious accuracy, but so does a lot of military ball, whether indented or not. In the end, it depends on whether the more critical influence on accuracy from a particular load in your particular gun is bullet shape or if it is consistency and adequacy of start pressure? In the former case, the indentation hurts; in the latter it helps. You just have to try it to find out which applies in your case?

Regarding taper crimps, bear in mind that people have been loading ammunition for a lot longer than the taper crimp was available. The first I heard of taper crimp dies was in the 70's. I may have missed them before then, but all the 1960's NRA loading manuals have photos of the .45 ACP roll-crimped.

Here's the thing: If you are shooting jacketed bullets, except in a high recoiling revolver load you don't usually need a crimp. You often don't even need to flare the case necks to seat jacketed bullets, either. The factories don’t. A good chamfer on the case mouth will often be enough.

Lead bullets are another matter. For one thing, they are lubricated. If you don't crimp a lubricated cast or swaged lead bullet, it is often possible to push the seated bullet deeper into a case with your thumb. This is particularly unsafe in a small capacity case because it will see a dramatic pressure rise if a bullet is seated even modestly deeper than the load was developed for. As a result, a crimp is needed to keep the bullet in an autoloader cartridge from being pushed in when recoil bumps the front edge of the magazine back against it. A light roll crimp or a firm taper crimp will engrave a lead bullet with a ridge that prevents this.

What about headspacing on the case rim? Well, truth to be told, most straight, as-issued 1911's and a lot of other self-loading pistols have enough slop that the chamber is actually too long to headspace most ammunition on the case mouth. Instead, the cartridge's forward location is regulated by the extractor hook. In the case of the .45 ACP, this doesn't seem to impact accuracy too badly when shooting jacketed bullets. They are tough enough so the case backs up against the breech face as the bullet works it way onto the rifling and more or less lines itself up. Lead bullets, on the other hand, engrave so easily that if they start out canted to one side by pivoting on the extractor hook, they enter the bore slightly canted, and that plays havoc with their accuracy.

So, what did all the old-time, pre-taper crimp softball shooters do? They headspaced on the bullet. You simply seat the bullet out a little further. Just enough that when you drop a loose round in the barrel, the face of the case head is flush with the breech face. In some extreme cases, where the barrel extension (hood) was welded for fitting but remained too long on a 1911, this headspacing setup made round nose bullets stick out too far to fit in the magazine. But with more blunt-shaped target and semi-wadcutter and truncated cone bullets, it usually isn't an issue. And, it can cut lead bullet group sizes in half, as it did for my original Goldcup.

For the 1911 in .45 ACP, barrel gauging headspace looks like the illustration below.



I also use taper crimp dies for lead target loads in revolvers. Why? The light loads don’t need a heavy roll crimp to prevent bullet back-out, and the taper crimp works the case mouth brass a lot less. The result is the cases last through many more reloads; as many as 50, while roll-crimped case mouths start splitting long before then.

Hope this helps,
Nick

[Ausserordeutlich]

I've just never been able to get beyond "oh dear." Guess it's my loss! I've never heard a man say, "oh dear."

[cheygriz]

This is an area where many of the experts strongly disagree. Try Different methods and see what works for you.

And as for the .45 "headspacing on the case mouth", I thought that myth had been put to rest decades ago.

[Unclenick]

Originally Posted by Ausserordeutlich

I've never heard a man say, "oh dear."

Try 30 years of marriage. It practically becomes a mantra; with and without a comma in between.

[Ausserordeutlich]

I meant to add a smiley. Should have done that.