Quote:
Originally Posted by daddySEAL
Factory crimp die needed for revolver ammo?
I've heard that it is important with semi-auto ammo reloading.
But is it needed for reloading revolver rounds?
|
Equally necessary for either type of action, revolver or semi-auto. Also, equally unnecessary.
The Lee FCD (for straight-walled cases; for bottlenecked cartridges the FCD is completely different) performs two functions. Some people derive benefit from both functions, some people from only one function or the other. Some people acutally derive a perceived detriment from one of the die functions.
Function 1 It crimps a bullet (already seated) and it crimps it without seating it any deeper. Seating a bullet deeper (as a combination seat/crimp die does) often causes the case mouth to "dig" into the bullet, as the bullet is moving at the same time as the crimp is being applied or buckle the case.
Making the crimp after the bullet has been seated and is no longer being pushed deeper makes it easier to 1) adjust the die and 2) relieves the "digging in" problem.
Not everyone experiences the digging in problem. It depends on the strength of the crimp and the shape of the crimping groove in the bullet. But it does make adjusting the dies easier. When you adjust the crimp on a combination seat/crimp die, the seating adjustment changes. It isn't HARD to do, but doing it in separate dies is easier.
Function 2 It sizes the cartridge case one last time. When inserting a bullet into a cartridge case, sometimes (especially if the bullet is a little oversize, which lead bullets tend to be for good reasons which I will not go into here and sometimes for bad reasons which I will not go into here, either) the case will bulge a little, especially if the case walls are thick. This sometimes interferes with good, reliable chambering.
The Lee FCD is equipped with a sizing ring that takes down any bulges. This helpd with some handloads. Hurts with some others, as it can inadvertently undersize the bullet inside the case.
If you post-size a round with a lead bullet, the brass is squeezed down and the lead slug is squeezed down also. When the cartridge is pulled completely out of the post-sizing ring, the brass springs back a little, but lead, being a less "springy" metal does not spring back nearly as much. The friction fit between the brass and the lead is thus less than if the post-sizing had never taken place.
Some reloaders go so far as to knock the post-sizing ring out of the FCD. (Incidentally, the same effect could be achieved by simply acquring a second seat/crimp die and pulling the seating stem back, or out. If using batch processing, just use the seat/crimp die a second time with the seating stem backed out.)
In summary:
The Lee FCD die does not replace the resizer die. The Lee FCD is a crimping die and it is supposed to help correct some sizing issues with cases. Some folks swear by them some folks swear at them.
Separating the crimping from the seating makes it easier to install/adjust the dies and makes the crimping operation (particularly for very strong crimps) easier to do without damaging the bullet or the cartridge case (buckling).
The bonus of post-sizing available with a separate crimping die is a blessing (and to some people, a curse) not possible if made part of a combination seat/crimp die.
An extra (or extra use of a) seat/crimp die can serve as a crimp die by simply removing the seating stem, but the post-sizing will not take place. This would be inconvenient on a progressive or autoindexing turret used in continuous mode, but convenient enough if processing in batch mode, as on a single stage or any press in batch mode.
Good luck
Lost Sheep