RCBS Case Forming Dies are used to create brass cases for very hard to find or expensive cartridges out of readily available brass. They are designed to change the case in small steps to eliminate excessive stress on the brass. After forming and trimming, the cases must be full length sized for final forming. These sets may consist of one trim die or a whole set containing up to three dies, expander ball, ream die and reamer depending on the case being formed. Instructions are included with each set.Case forming dies are for the reloader interested in forming cases from one caliber to another. This is done either
because the case needed is prohibitively expensive or it is otherwise unavailable.
The specific steps necessary to form cases will vary greatly depending on what changes must be made to the parent
case and may include initial forming, separate base forming, annealing the brass, making the neck larger or smaller, cutting
the cartridge rim and fireforming the case in the firearm's chamber to obtain the finished caliber.
Case forming dies are designed to reduce the case by steps to eliminate case stress or collapse and to prolong case life.
There will be one or more form dies for each caliber. After forming and trimming, cases must then be full length sized, using
the full length sizer in the reloading die set for the finished caliber. RCBS does not recommend using full length sizer dies for
the actual case forming process.
Case forming dies (threaded standard 7/8 x 14 unless otherwise noted) will withstand the normal case forming pressures
encountered but are not intended to swage the base of the case. When that is required, a special Base Form die is needed.
Base Form dies are unthreaded and require the use of a 3-ton arbor press.
Some cases will need to be shortened after initial forming. A Trim Die is designed so that a mill type file can be used to
trim the case to the correct overall length without damaging the surface of the die.
Frequently, changes to a case will result in brass that is too thick at the case's neck. A Neck Reamer, if needed, may be
chucked in a tap wrench or in a hand drill. A drill press is not recommended.
A search of MidwayUSA's product offering using "RCBS" followed by the name of the specific finished caliber
needed will give a listing of all the RCBS dies available and may help to show what will be needed in that specific case-
Caliber-specific information and general instructions on case forming can be found in "The Handloader's Manual of
Cartridge Conversions" by John J. Donnelly, product number 815626, and in "Designing and Forming Custom
Cartridges" by Ken Howell, product number 942114.
RCBS is also available at 800-533-5000 between 6:30 AM and 3:00 PM Pacific time Monday through Friday for
questions about what will be needed to form cases.