Redding’s Dual Ring Carbide Sizing Die
Date: Jun 01 2012
Redding has recently introduced a patent-pending Dual Ring Carbide sizing die for popular straight-walled pistol and revolver cartridges, addressing the problem of handloaded cartridges often being excessively loose in the chamber – and other issues.
The lower carbide ring sizes the case minimally, but nonetheless brings the lower half of the fired case back to industry specifications and is a full-length sizer. This is important, as revolver rounds must have some “play” in the chamber, or they can drag on the recoil shield, hindering reliability. By “working” the lower half less, case life is longer. Redding is claiming that it even improves accuracy, which is probably true. It also largely eliminates the “wasp-shaped” case that is common with cartridges that are loaded using some traditional carbide dies.
The second, or upper, carbide ring sizes the upper portion (or neck) of the case small enough so it fits tightly in conjunction with seated bullets. This plays an important role in preventing bullet jump, obtaining proper powder ignition when using slow-burning powders often associated with magnum revolver cartridges, helping to lower extreme velocity spreads and aiding accuracy. A heavy bullet pull will even bump velocity when compared to ammunition loaded in dies that feature a rather loose bullet-to-neck fit. When using cast bullets, this tight bullet and case relationship help to seal the bullet lube, helping prevent contamination of the powder.
With the upper carbide ring sizing the case mouth to a smaller diameter than the lower part of the case, it is a similar concept as neck sizing cases; however, as mentioned, reloaded cartridges will fit in any gun that has a SAAMI specification chamber. From around 1980 through 1987, I did considerable experimenting with neck sizing revolver cases, and while those findings often resulted in improved accuracy and longer case life, I gave it up for a couple of reasons. Ammunition often needed to be used in multiple guns and usually would not chamber reliably in other revolvers. And some guns had out-of-round chambers that resulted in neck-sized ammunition that either had to be forced in or turned until it would chamber, which is impractical for a gun that is carried in the field or for business.
Dual carbide rings sound simple enough, but to work properly, they must be perfectly centered with each other. If not, the sized case would essentially be bent into an L shape, which would bring on a host of other problems. Redding has put in considerable effort to assure that the rings are in perfect alignment.