KM Expander Mandrel


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SKU: C1016 Category: Tag:


KM Expander Mandrel – Neck turning preparation

  • The KM Expander mandrels bolt into a special press adapter to be used to internally expand (usually virgin brass) prior to neck turning operations using the KM Neck Turners.
  • These expanders fit into the KM Press Adapter (sold separately)
  • They are sized approximately 0.001″ larger than the KM brand neck turner mandrels (all 3 types of KM neck turn mandrels).
  • This is to allow for brass spring back of new cases giving a good fit of the inside necks on those mandrels. Without a proper fit the final results of outside neck turning will provide variations.
  • The actual size of the KM expanders is usually close to actual caliber size (eg: for 30cal will be 0.308″, for 6mm will be 0.243″)
  • These expanders have a unique depth control adjustment also. Set to bottom out on the inside case web. This means they can also be adjusted carefully to assist in removal of internal case neck ‘donuts’ by expanding down to, but not over the ‘donut’. (separate tools required to cut out donuts)

NB: For other expanding operations, to uniform inside of necks and control bullet grip after resizing (especially using Neck bushing type dies) the KM Custom undersize mandrels are made for those tasks (separate product).


What’s included? 1 x Expander mandrel with depth control bolt and securing bolt for the press adapter (press adapter sold separately. Also consider a Window riser for press adapter)

(6mm-30cal, 172, 204, 224, 243, 257, 264, 277, 284, 308, 311, 315, 338. 357, 366, 375, 408, 416)

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