« Reply #4 on: February 06, 2021, 02:22:37 PM »
RELOADING DIES
To reload successfully, the novice needs to learn how reloading dies work, and then how to adjust reloading dies to get them to function properly. True, brand new dies can have issues right out of the box, but this is a very, very rare occurrence. It's always easier to blame the die maker when issues arise, but most die issues are simply created by improper die adjustment. Furthermore, when issues do occur, if the user doesn't fully understand how dies work, then they can waste a lot of time adjusting or replacing the wrong die.
The Most Important Thing to Understand
The most important thing to realize about reloading dies is just how sensitive they are to adjustment. A lot of the dimensions within the chamber and typical cartridge are equal to one half the diameter of a human hair. It's OK to be a macho Rambo when you load that magazine and slap it into your CZ pistol. However, when you adjust your dies to make that ammo you need to have the deft touch and finesse of a watch maker. If you can't make that transition, then you'll never have very much success at reloading.
Here's an example why... Adjusting the taper crimp is accomplished by moving the body of the die. Almost all die bodies come with a 7/8-14 thread. That nomenclature tells us the thread pitch is 14 threads per inch. In other words, that one full turn advances the die 1/14th of an inch, or 0.071". If you wish to change the die setting by 0.002" then you only need to turn the die less than 1/35th of a turn. So if you think you can set your dies by moving them in 1/8 turn increments, think again. You need to work in terms of adjustments more than 4.5 times smaller than that !
So leave your big Rambo muscles at the door, and forget everything you ever learned pulling wrenches on a car. Die adjustments are the most delicate settings you can make. They require abundant skill and very high sensitivity. This is the Science of Reloading.
Brass Spring-Back
Initial die adjustments are made with a box full of fired brass cases. The first thing to realize is that brass has a "springy" quality which can make small adjustments impossible. While it will be easy to move a flair diameter by 0.004 to 0.010", due to spring back it becomes nearly impossible to move brass by only 0.002". So as you close in on the desired dimension, it's important to use a new piece of brass for every measurement check.
How Pistol Dies Work
It seems fairly simple, but many users simply don't understand how dies work.
1. Sizing simply changes the external shape of the brass cartridge case, but it is not a consistent change over the entire case length. About 85% of the main body of the cartridge case is returned to standard chamber dimensions. The neck of the case that holds the bullet is taken to an undersized state. Sizing does not prepare the case for the bullet holding. Sizing is an action on the case exterior; bullets are always held in place by preparations to the case interior.
• Due to brass "spring-back" and the different maker's case wall thicknesses, Sizing takes the case mouth to a diameter far smaller than what is needed for bullet grip.
• Due to the shell holder's grasp of the case rim, Sizing cannot reach the area around the case head. It is common for over-pressure and Major PF rounds to expand this area and render cases non-reusable.
2. Expansion is a secondary step that prepares the case interior to grip the bullet. It takes the under-sized case neck left by Sizing, and opens it up to a precise internal dimension that will adequately grip the bullet. This is typically 0.002-0.003" smaller than a jacketed bullet.
3. Belling prepares the case mouth for the entrance of the bullet. Expansion has left the case mouth smaller than the bullet diameter and so a funnel shape is required to allow the larger bullet to enter. The Belling function is typically included with Expansion tool, but they are 2 separate functions.
4. Seating is also a multi-step process. The bullet should first be straightened and aligned with the case mouth. Then the seating stem then should insert the bullet into the case mouth to the proper depth.
5. Crimp is a swaging action that erases the case's Belling. Typically revolver cartridges require a roll crimp, where a tiny portion of the case mouth is rolled into a cannelure provided on the bullet. Typically taper crimp is used on auto pistol cartridges. Taper crimp does not "hold the bullet". Therefore, more taper crimp does not hold the bullet tighter.
Static Pistol Die Adjustment
We'll be concentrating on "straight-walled" pistol die adjustments in this section, but "bottleneck" rifle die adjustments are similar in many respects. Most reloading dies do more than a single function, which usually means there is a mandatory adjustment sequence. The die body is always adjusted first, followed by the stem. If the body is ever moved, then the stem will also need readjustment.
• Sizing Die. On straight-walled brass you'll want to resize as much of the case's side wall as possible. That means the Sizing Die should come down over the case as far as possible. However, the die should not come into contact with the shell holder. Most modern Sizing Dies incorporate a carbide insert, and carbide is about as fragile as glass. If the shell holder is allowed to bump the die, there is a chance that the carbide will shatter, making the die useless. So it is best to leave a clearance of 0.003 to 0.005" between the die body and shell holder. If you can pull a strip of printer paper between the 2 parts when the ram is fully raised, and feel a slight drag, then you have an optimal Sizing Die position.
The decapping pin length is set next. You want the pin as low as possible without contacting the brass. This typically exposes about 0.19" of pin from the die body.
• Expander. On a singe-stage press you may use an Expander Die. If you use a progressive press, the expander function is most likely built into a part of the powder measure. Both methods typically include the expansion function with the belling function. The die is properly set when the case mouth belling is just barely large enough to seat a bullet without shaving any material from the shank. The belling is adjusted to initially flair a sized case by 0.008 to 0.010".
A typical 4-function Expander from a progressive press
• Seating Die. Most seating dies use the die body to apply a crimp: roll crimp for revolvers and taper crimp for automatics. Setting the crimp is a 2 step procedure. 1) Move the die downward in tiny increments onto an assembled test cartridge (no primer, no powder) until the crimp forms. 2) Since height of the case effects final crimp diameter, and since all cases vary in length there will always be variations in crimp. Therefore, it always best to average the results of 10 crimps, rather than use the results of a single test case.
If you have a progressive press with more than 3 stations and you desire to crimp at a separate station, then run the die down until it touches the case, and then raise the Seating Die body ~1/4 turn.
Typically, the inner stem adjusts the seating depth of the bullet (otherwise known as cartridge over-all length, or OAL). Again there will always be variations in OAL, so it is always better to average the results of 10 test cartridges when adjusting the seating stem. OAL variations of +/-0.002" are considered excellent.
Wider variations in OAL can be introduced by inconsistent operation of the op lever, lack of case lubrication, variations of brass hardness due to "mixed brass", and seating stems (or anvils) that do not properly fit the ogive of the bullet. A proper seating stem will straighten and center the bullet before seating, and then seat the bullet without leaving a blemish on the bullet's ogive.
• Crimp Die. Separate crimp dies are preferred for use in progressive presses. Crimps fall into 2 categories: roll crimp for revolvers and taper crimp for automatics. Adjusting the crimp is a 2 step procedure. 1) Move the die downward in tiny increments onto an assembled test cartridge (no primer, no powder) until the crimp forms. 2) Since height of the case effects final crimp diameter, and since all cases vary in length there will always be variations in crimp. Therefore, it always best to average the results of 10 crimps, rather than use the results of a single test case.
• There are more details on taper crimp HERE.
• If you prefer to use the Lee Factory Crimp Die (FCD) then follow the instructions supplied with the die.
Again, these were static die adjustments. Once production begins, the user needs to go back through and check all the case measurements again because dynamic forces within the press will sometimes alter the die adjustments. This is especially true on multi-position progressive presses.
Reference Dimensions
The following is a list of optimal die and case measurements for reference. - | | 40cal / | |
- | 9mm | 10mm | 45ACP |
. | . | . | . |
Bullet OD | 0.355 | 0.401 | 0.451 |
Szd Cse Mth OD | 0.373 | 0.416 | 0.466 |
Expander OD | 0.3525 | 0.3970 | 0.4470 |
. | . | . | . |
« Last Edit: March 10, 2021, 03:44:54 PM by Wobbly »
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