Taper, Trim, and Neckdown

After head turning, the case is slightly longer than the finished product and is a near-perfect cylinder. Most cases are ultimately tapered to some degree. The case is run into a die. If a small taper is needed, one die can suffice; for more pronounced tapers, the taper is produced progressively to reduce stresses.

Many rifle cartridges have a distinct bottlenecked shape. The neck and shoulder that create the bottleneck shape are also produced in a die or in a series of dies (if the neck diameter is much smaller than the case body).

Once the final profile is formed, the case is trimmed to the specified length. Trimming can be performed on a machine with a cutter that is moved to work the open end of the case (similar to the head-turning machine). Trimming can also be performed in a machine with a rotating cutter; the cutter axis aligns with the case axis. It moves down onto the case mouth, and a preset stop halts the cutter when the correct length is reached.

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