Universal Pump Chassis

universal pump chasis 3d print

Universal Pump Chassis STL Files

Multi-caliber pump-style firearm

Mouse, Maker. Maker, Mouse.

The BCAM Universal Pump Chassis is a seriously bada** multi-caliber pump-style firearm that uses off-the-shelf AR15 parts.

Shop Husky Armory

If there was ever a contest for “Most Neapolitan GunCAD Release,” the UPC from Black Cat Aircraft and Manufacturing would be front of mind as a candidate. Boasting a surprising collection of compatible cartridges, including a wildcat with no official SAAMI specs, this one’s got something to offer everyone, regardless of taste.

An experienced dev and valued member of the Black Lotus Coalition, BCAM is one of GunCAD’s many open and proud transgender voices, exemplifying our long-standing tradition of amplifying the Signal no matter where it comes from.

In The Wild

Technical Specs

The files are designed to accommodate PLA+ as a minimum. Durability may vary depending on selected print materials.

Documentation is scarce with this release, despite its relative complexity and scope, and not much information is available across both Odysee and DEFCAD, but the file package does include a how-to video filmed by BCAM that demonstrates how the pieces all go together.

It should be noted that the video features BCAM building a UPC in .50 Beowulf, but assembly does not seem to be affected significantly by cartridge choice.

The design is meant to support standard AR-15 parts and can be made compatible with the following cartridges:

  • .223 Remington/5.56 x 45 NATO
  • .224 Valkyrie
  • .25-45 Sharps
  • 6.5 Grendel
  • 6.8 SPC
  • .300 AAC Blackout
  • 7.62 x 39
  • .338 Spectre
  • .450 Bushmaster
  • .458 SOCOM
  • .50 Beowulf

Parts List


  • AR-15 barrel (carbine length gas port, 10″ minimum)
  • AR-15 BGC
  • AR-15 FCG (sans safety)
  • AR-15 buffer spring (carbine length)


  • 23 – M5 x 25mm Allen drive grip head bolts
  • 1 – M5 x 35mm Allen drive grip head bolt
  • 3 – M4 x 30mm Allen drive grip head bolts
  • 1 – M4 nut
  • 6 – M5 heat inserts
  • 4 – M4 heat inserts
  • 1 – Steel bar (2″ W x 1/8″ H)
  • 1 – 1/4 x 20 All-thread rod
  • 10- 1/4 x 20 nuts
  • 1 – 3/4″ ID shaft collar, OD >1 ¼”
  • Thread locker


  • Knife
  • Allen keys
  • Drill and bits
  • Taps
  • C-clamp or bench vice
  • Hammer
  • Metal saw or grinder
  • File (mill)
  • Wrench
  • Soldering iron

Build Instructions

Flexible and versatile, the Universal Pump Chassis is built like no other. Download and 3D print one today!

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DISCLAIMER: 3D STL files are for learning and documentation purposes only. The users of this website and files need to be aware of all applicable local, state, federal and regional laws. 3D Gun Builder does not encourage, condone, or promote any illegal activity.

3D Gun Builder (3dgunbuilder.com) does not host, provide, develop, and/or have any affiliation with the firearm STL files or 3dgunvault.com. All files are hosted by a third party.

Kem Regik
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