Manurhin PB-31-8 Bullet Assembly Press

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The Manurhin PB-31-8 is a mechanical multi-stage transfer press manufactured by the French company Manufacture du Haut Rhin (MHR). MHR is a global leader in industrial ammunition manufacturing equipment, and their PB series is an industry standard for projectile production.

This specific machine is used for the automated manufacturing and final assembly of the projectile (the bullet) for small-caliber ammunition.

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Primary Function & Input Materials

The primary task of the press is to mechanically join the bullet's jacket with its core. The machine is fed with two primary input materials:

1. Cup blanks (pre-drawn metal cups, typically made of brass, tombac, or steel, which will form the outer jacket).

2. Pre-formed lead cores (or sometimes steel penetrators, depending on the ammunition type).

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Technical Working Principle

• Transfer Mechanism: As a transfer press, it is equipped with an automated feeding mechanism (transfer bar) that moves the workpiece linearly from one tooling station to the next with each stroke of the press. 

• 8 Processing Stations: The number "8" in the model name indicates the number of tooling stations in the machine. A bullet is gradually completed as it passes through these stages. For a standard Full Metal Jacket (FMJ) pistol bullet, the operational sequence is typically set up as follows:

  1. In-feed of cup and drawing

  2. Point forming

  3. Trim jacket length

  4. Insert lead core

  5. Close base of bullet

  6. Final form

  7. Empty (Idle station)

  8. Calibration (Final diameter sizing)

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Production Speed​​​​

• Operating Speed: Machines of this type typically operate at a speed of 60 to 120 Strokes Per Minute (SPM).

• Output Rate: Since a transfer press completes one projectile for every stroke (once fully fed through all 8 stations), this equates to 60 to 120 finished bullets per minute.