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6 mm Reducer for UMAREX HDS 68

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  • 1 download

Licence CULTS - Private Use
Publication date 2023-03-05 at 14:35
Design number 1099462
3D design format
STL Folder details Close
  • R68_T8E02_Centreur_Trou825.stl
  • R68_T8E02_Centreur_Trou835.stl
  • R68_T8E02_Culasse_Trou825.stl
  • R68_T8E02_Culasse_Trou835.stl
  • R68_T8e02_Cart2x6.stl
  • R68_T8e02_Cart3x6.stl

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3D printer file info

3D model description

Uploaded on 05 March 2023

Created with: tinkercad

The HDS68 defensive rifle uses a Co2 cartridge and can fire 2 .68 caliber rubber bullets (or Paintball) with a power of 16 Joules.

For recreational target shooting, I have created a caliber reducer that allows you to shoot 6mm steel balls, so your rifle turns into a very powerful rifle! For this, I use a brass or copper tube ...

As the HDS 68 has no sighting system, you can add a laser on the Picatinny rail under the barrels, or a Red Dot sight on the top thanks to the free Picatinny rail I propose here :

Materials to be purchased:

  • A copper or brass tube of 8 mm diameter, 0.20 mm wall, 200 mm length. It will fit into a "breech" at the back and a "centering device" at the front (see photos).

  • a neodymium magnet of 10 mm in diameter and 2 mm thick (available among others on amazon).


  • force the tube into the "breech" (if it is too tight, immerse the assembly in water at 50-60°C).

You will find in my kit 2 breeches and 2 centering, with internal diameters of 8.25 or 8.35 mm .

  • at the other end of the tube test the fit of the centering device: it must be able to slide but tight. Once done, remove it from the tube.

  • glue the magnet on the flat part of the breech with Superglue (its purpose is to maintain the cartridges in the breech by attracting the balls).

  • Place the breech-tube assembly in a barrel of the weapon, then fit the centering device to the front, without sticking.


Simply insert a cartridge (containing either 2 or 3 beads) into the breech, its base must touch the beginning of the tube.

Weight of the cartridges :

  • with 2 balls : 2.22 g

  • with 3 balls : 3.04 g

Velocities raised WITH A 300 mm LENGTH TUBE (they will be less with a 200 mm tube):

  • with 2 balls : 240 to 270 f/s

  • with 3 balls : 174 to 190 f/s


To be used exclusively for recreational shooting!

The use of this ammunition is much more dangerous to injure than the original rubber bullet!

Here in France, in case of injury to a possible attacker, you will risk criminal prosecution ...

  • to see my other ammunition for HDS68 and HDR50, go further down this page!

  • for my other creations on this site, enter "oasisk" in the search window, or click on the "all >" button on the "other 3D models of the same designer" line

3D printing settings

layer: 0.20

filling: 20% for all elements

raft: no

support: no

skirt: yes in order to start the extrusion


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