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JamesRPatrick PM522 Washbear .22LR Revolver






Copyright 2015 distributed under the GNU General Public License v3.0 (GPLv3).

Release Date



This is a 6-shot, double-action-only 3D-printed pistol chambered in .22LR. A roofing nail is used as the firing pin, and elastic bands are used as springs. Steel barrel or chamber liners are not required but will significantly extend the life of the cylinder. The cylinder version that accepts chamber inserts has a capacity of 8 rounds. When the trigger is at rest in the forward position, the cylinder is rotated such that the firing pin is not in line with any cartridge, making this firearm drop-safe. 100% printed barrels are not intended to have a long service life. Works best with subsonic ammunition.

Special thanks to FP of FOSSCAD for printing and test firing this design.

Test Fire

Test Record

  • 2015/09/13 Version 1.0 Tension Cylinder Assembly was printed in ABS. It failed after three shots. The tension bars and cylinder core sheared cleanly at the point where the bullet sits in the chamber.

  • 2015/09/18 Version 1.1 Resin Cylinder 1v3 was printed in ABS and filled with fiberglass and resin. It fired all six shots but was damaged beyond repair. The chambers cracked between layers.

  • 2015/09/23 Version 1.1 Solid ABS Cylinder Assembly with steel chamber inserts fired all six shots succesffully.

  • 2014/10/01 Version 1.1 Solid Nylon Cylinder Assembly (Taulman Bridge) fired five shots without damage. [World Record!]

  • 2015/11/15 Version 2.0 Solid ABS Cylinder Assembly with steel chamber inserts fired all eight shots successfully.


  • Requires a print bed of at least 11" diameter or at least 10" x 6" rectangular area.
  • All printed parts are to be printed with 100% infill, with maximum shells. Print in ABS unless otherwise instructed.
  • If using chamber inserts, the cylinder parts may be printed in ABS.
  • If using a 100% printed Cylinder Assembly, the Front Cylinder Assembly and Rear Index Ring MUST be printed in Nylon. Taulman Bridge is the only successful filament so far.
  • Use plenty of support material.
  • Print Frame and Grip on their right sides.
  • Print Front Cylinder Assembly standing on its front end (larger end).
  • Print Trigger on its left side.
  • Print Striker, Guide Rod, and Sear on their sides.


  • Some parts require epoxy to assemble. Use a high strength epoxy made for ABS and Nylon, such as Loctite Epoxy Plastic Bonder.
  • Install the legally required amount of detectable metal in the Grip using high-strength epoxy. Use acetone or epoxy to secure the Grip Cap.
  • Use a 2mm, a 6mm, and an 8mm drill bit to ream appropriate holes.
  • Use 1.75mm filament to secure the Grip Pin.
  • Use a 1", 12 Gauge roofing nail with 0.281" head. 12 gauge is 2.680mm diameter.
  • Grind tip of Firing Pin to a horizontal, 1mm-wide blade with 0.040" MAX protrusion. Trim the nail head to fit in the Striker. See CAD for dimensions.
  • Use epoxy to secure the Firing Pin to the Firing Pin Retainer.
  • Use epoxy or acetone welding to secure the Firing Pin and Firing Pin Retainer inside the front of the Striker.
  • Use rubber bands or condoms to power the Striker, Trigger, and Sear. 1/4" dental bands have been used successfully.
  • Use epoxy or acetone welding to bond the Rear Index Ring to the Front Cylinder Assembly. Sand rear surface of the Cylinder to fit.
  • Chamber inserts are cut from 9/32" OD, 0.225" ID, 0.028" Wall 316 Stainless Steel tubing. McMaster-Carr part #1800T301
  • Cut tubing into 34mm lengths and deburr.
  • See renders for part layout.


  1. Changes from 1.0:
  • Thickened Tension Bars and modified cylinder assembly parts to fit Tension Bars.
  • Thickened frame above cutout for cylinder assembly.
  1. Changes from 1.1:
  • Moved the firing pin location to 2 o'clock position. Modified the Frame, Striker, Firing Pin Retainer, and Firing Pin to accommodate this.
  • Added a tab to the Firing Pin Retainer and coresponding notch in the Striker to ensure proper assembly.
  • Moved bores farther from axis of cylinder by 1.5mm. Modified Frame to accommodate this.
  • Small cosmetic change to the bottom of the Grip.
  • Added tab to Sear Pin and corresponding notch in Trigger to allow for disassembly of these parts (no adhesive required now).


Use this information at your own risk and responsibility.

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