FAQ

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Arbor Press Builder and Accessories-843
Arbor Press
Mitutoyo Wall Thickness Micrometer with 60 Degree Modification-0
Case Neck Thickness

Arbor PressArbor Press Builder and Accessories-843

  • Bullet Seating Force – Which Force Pack Do I Need?
    • The standard and low force pack will measure bullet seating force. This will indicate if there are inconsistencies/variables upstream that can be improved.
    • There is more information at the bottom of the Arbor Press page, including this info: https://kmshooting.com/product/arborpressbuilder/
      • For determining the correct force pack to use, the decision point between the standard force pack and the low force pack is based on the neck tension that the neck has been sized for. The typical rule of thumb for the use of the low force pack is neck tensions of .0015-.002” or less. The scale on the low force pack is 0-50lbs. Therefore, when seating with light neck tensions you will have better resolution for lower force readings.
      • The standard force pack range is 0-150 lbs which will accommodate pretty much any neck tension.
    • There’s also some good photos and info in the tool instructions here: https://kmshooting.com/wp-content/uploads/2021/03/Arbor-Press-2021.pdf

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Expand Mandrels

  • Please explainBullet Tension Mandrels
    • Mandrels for bullet tension are stocked in popular sizes
      • There is a selection on the website (.17 to .50 cal from .0010 to .0050” bullet tension)
      • Any size for .17 to .50 BMG is possible with an e-mail to [email protected]
        • We grind custom mandrels once every week
    • Each mandrel is laser etched with caliber and “.00XX BT” ; it’s on the shank that goes into the press adapter
    • We size our mandrels for the spring back of nominal annealed brass
      • The snap back is a function of diameter and not a constant value
      • Our gage pins help to confirm the neck diameter and brass snap back
        • If the gage pin slides in without holding air pressure, resize the neck one or more times to work harden the brass and cause more snap back to achieve the desired ID
        • If the gage pin is tight or doesn’t fit, anneal the brass to reduce the spring back
    • Our bullet tension and neck turning mandrels are made from the same hardened steel blank, but not made to the same tolerance.
      • The neck turning mandrels are ground to a wider tolerance than the mandrels for bullet tension.
      • Since the mandrels for bullet tension are made in .0005” increments, we must hold them to millionths of an inch so there isn’t overlap between graduations.
  • Help! I cannot add mandrels to cart
    • The likely issue is a box that needs to be checked at the bottom of the page – shown below in green “I understand this is a custom made tool and not refundable.

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Flash Hole Uniformers

  • What size should I get?
    • The flash hole can vary depending on the brass manufacturer and doesn’t necessarily follow the primer size. Many use the “standard” .080” flash hole while Lapua can have a small flash hole .059”/1.5mm.
    • We recommend checking with a drill bit, shank non-cutting side, to determine which size you have:
      • .08 flash hole: 5/64” (.0781”) drill bit
      • .059/1.5mm flash hole: a 1/16” (.0625”) or #54 (.0550”) drill bit
    • Another option is measuring your de-capping/de-priming pin. If the pin is larger than .06” and fits loosely in the flash holes – you’ve got .08” flash holes.
      • If your pin is smaller than .06” you’ll need to confirm with drill bits or other diameter pins
  • What’s the Different Between Premium .059 vs Pro/Premium .062?
    • Premium .059 vs. .062 comes down to opinion:
      • The .062 will provide uniform hole size for “1.5mm” (.059) flash holes by opening the flash hole by .003”
      • The .059 will chamfer the hole, clean up undersized flash holes and leave any oversized flash holes as-is
  • Explain Professional vs. Premium

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